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Sample records for near-threshold rovibrational excitation

  1. Near Threshold Excitation of Molecular Nitrogen: Benchmarking Cross Sections for Upper Atmospheres

    NASA Astrophysics Data System (ADS)

    Malone, C. P.; Johnson, P. V.; Hein, J. D.; Grisanti, B.; Khakoo, M. A.

    2013-12-01

    Molecular nitrogen is the major component in the atmospheres of Earth, Titan, and Triton. The airglow emissions of N2 from the atmospheres of Earth and planetary satellites have been extensively observed. Accurate, consistent cross section data is a necessity for accurate models of how upper atmospheres behave. We present electron energy-loss (EEL) derived excitation cross sections for near-threshold electron impact of N2. Differential cross sections (DCSs) and integral cross sections (ICSs) were obtained by unfolding EEL spectra in the ~6-11eV range for the A 3Σu+, B 3Πg, W 3Δu, B‧ 3Σu-, a‧ 1Σu-, a 1Πg, w 1Δu, and C 1Πu electronic states over the ~15-130° scattering angular range. Vibrationally-resolved DCSs and ICSs were obtained for stronger vibronic transitions, including the a 1Πg state, which generates the atmospherically important Lyman-Birge-Hopfield (LBH) emissions. The summed near-threshold excitation cross sections (A+...+C) generally are larger than previous measurements. Acknowledgement: This work was performed at CSUF and JPL, Caltech, under contract with NASA. We gratefully acknowledge financial support through NASA's PATM and GEO programs and NSF-PHY-RUI-0965793.

  2. Photoionization cross section measurements of the excited states of cobalt in the near-threshold region

    SciTech Connect

    Zheng, Xianfeng Zhou, Xiaoyu; Cheng, Zaiqi; Jia, Dandan; Qu, Zehua; Yao, Guanxin; Zhang, Xianyi; Cui, Zhifeng

    2014-10-15

    We present measurements of photoionization cross-sections of the excited states of cobalt using a two-color, two-step resonance ionization technique in conjunction with a molecular beam time of flight (TOF) mass spectrometer. The atoms were produced by the laser vaporization of a cobalt rod, coupled with a supersonic gas jet. The absolute photoionization cross-sections at threshold and near-threshold regions (0-1.2 eV) were measured, and the measured values ranged from 4.2±0.7 Mb to 10.5±1.8 Mb. The lifetimes of four odd parity energy levels are reported for the first time.

  3. Prestimulus Network Integration of Auditory Cortex Predisposes Near-Threshold Perception Independently of Local Excitability.

    PubMed

    Leske, Sabine; Ruhnau, Philipp; Frey, Julia; Lithari, Chrysa; Müller, Nadia; Hartmann, Thomas; Weisz, Nathan

    2015-12-01

    An ever-increasing number of studies are pointing to the importance of network properties of the brain for understanding behavior such as conscious perception. However, with regards to the influence of prestimulus brain states on perception, this network perspective has rarely been taken. Our recent framework predicts that brain regions crucial for a conscious percept are coupled prior to stimulus arrival, forming pre-established pathways of information flow and influencing perceptual awareness. Using magnetoencephalography (MEG) and graph theoretical measures, we investigated auditory conscious perception in a near-threshold (NT) task and found strong support for this framework. Relevant auditory regions showed an increased prestimulus interhemispheric connectivity. The left auditory cortex was characterized by a hub-like behavior and an enhanced integration into the brain functional network prior to perceptual awareness. Right auditory regions were decoupled from non-auditory regions, presumably forming an integrated information processing unit with the left auditory cortex. In addition, we show for the first time for the auditory modality that local excitability, measured by decreased alpha power in the auditory cortex, increases prior to conscious percepts. Importantly, we were able to show that connectivity states seem to be largely independent from local excitability states in the context of a NT paradigm.

  4. Prestimulus Network Integration of Auditory Cortex Predisposes Near-Threshold Perception Independently of Local Excitability

    PubMed Central

    Leske, Sabine; Ruhnau, Philipp; Frey, Julia; Lithari, Chrysa; Müller, Nadia; Hartmann, Thomas; Weisz, Nathan

    2015-01-01

    An ever-increasing number of studies are pointing to the importance of network properties of the brain for understanding behavior such as conscious perception. However, with regards to the influence of prestimulus brain states on perception, this network perspective has rarely been taken. Our recent framework predicts that brain regions crucial for a conscious percept are coupled prior to stimulus arrival, forming pre-established pathways of information flow and influencing perceptual awareness. Using magnetoencephalography (MEG) and graph theoretical measures, we investigated auditory conscious perception in a near-threshold (NT) task and found strong support for this framework. Relevant auditory regions showed an increased prestimulus interhemispheric connectivity. The left auditory cortex was characterized by a hub-like behavior and an enhanced integration into the brain functional network prior to perceptual awareness. Right auditory regions were decoupled from non-auditory regions, presumably forming an integrated information processing unit with the left auditory cortex. In addition, we show for the first time for the auditory modality that local excitability, measured by decreased alpha power in the auditory cortex, increases prior to conscious percepts. Importantly, we were able to show that connectivity states seem to be largely independent from local excitability states in the context of a NT paradigm. PMID:26408799

  5. Near-threshold vibrational excitation of H sub 2 by electron impact: Resolution of discrepancies between experiment and theory

    SciTech Connect

    Buckman, S.J.; Brunger, M.J.; Newman, D.S. ); Snitchler, G.; Alston, S.; Norcross, D.W. ); Morrison, M.A.; Saha, B.C.; Danby, G.; Trail, W.K. )

    1990-12-24

    New measurements and calculations of near-threshold (0.5--5.0 eV) {ital e}-H{sub 2} vibrational-excitation cross sections challenge previous determinations based on transport analysis. Elastic and {ital v}{sub 0}=0{r arrow}{ital v}=1 cross sections measured in a crossed electron-molecular-beam apparatus agree well with values calculated using a vibrational close-coupling theory with a separable represetnation of exchange, particularly at energies below 2.0 eV, but are incompatible with cross sections derived via analysis of electron-swarm transport data.

  6. Parabolic versus spherical partial cross sections for photoionization excitation of He near threshold

    SciTech Connect

    Bouri, C.; Selles, P.; Malegat, L.; Kwato Njock, M. G.

    2006-09-15

    Spherical and parabolic partial cross sections and asymmetry parameters, defined in the ejected electron frame, are presented for photoionization excitation of the helium atom at 0.1 eV above its double ionization threshold. A quantitative law giving the dominant spherical partial wave l{sub dom} for each excitation level n is obtained. The parabolic partial cross sections are shown to satisfy the same approximate selection rules as the related Rydberg series of doubly excited states (K,T){sub n}{sup A}. The analysis of radial and angular correlations reveals the close relationship between double excitation, ionization excitation, and double ionization. Opposite to a widespread belief, the observed value of the asymmetry parameter is shown to result from the interplay of radial correlations and symmetry constraints, irrespective of angular correlations. Finally, the measurement of parabolic partial cross sections is proposed as a challenge to experimentalists.

  7. Dominance of the first excitation step for magnetic circular dichroism in near-threshold two-photon photoemission

    NASA Astrophysics Data System (ADS)

    Hild, K.; Schönhense, G.; Elmers, H. J.; Nakagawa, T.; Yokoyama, T.; Tarafder, K.; Oppeneer, P. M.

    2012-01-01

    Magnetic circular dichroism (MCD) in near-threshold photoemission is measured for a perpendicularly magnetized Cs/Co/Pt(111) film with work function adjusted by Cs adsorption. For one-photon photoemission (1PPE) the MCD asymmetry is recorded at a fixed photon energy of hν = 3.06 eV and varying work function Φ. The asymmetry shows a nonmonotonous behavior in dependence of the excess energy hν-Φ with a maximum value of A1PPE = 6.2 % at Φ = 2.45 eV. The measurement explores the first excitation step of a former two-photon photoemission (2PPE) measurement with A2PPE = 8.4% demonstrating that in 2PPE from Co(111) the first excitation step is the dominant asymmetry-generating process. An energy-dependent measurement in 2PPE at reduced work function (Φ≈ 3 eV) yields a constant asymmetry of about 17% in the photon energy range between hν = 1.53-1.66 eV. It reveals that for Co(111) the involvement of a real intermediate state is crucial for enlarged MCD asymmetries. Both results are discussed in the framework of direct interband transitions in directions deviating from the direction of normal electron emission Γ-L. The 1PPE measurement is in reasonable agreement with calculations on the basis of this model. This reveals that an ab initio calculation considering all directions of excitation with an additional restriction in energy due to the existence of the sample work function in the photoemission process adequately describes MCD asymmetries in near-threshold photoemission.

  8. Recent experiments on near-threshold electron-impact excitation of multiply charged ions

    SciTech Connect

    Bannister, M.E.; Djuric, N.; Woitke, O.; Dunn, G.H.; Chung, Y.; Smith, A.C.; Wallbank, B.

    1998-09-01

    Some recent measurements of excitation of multiply charged ions by electrons studied in beam-beam experiments are highlighted. The emphasis is on absolute total cross sections measured with the merged electron-ion beams energy-loss (MEIBEL) technique, although some results obtained with the crossed-beams fluorescence method are also presented. The MEIBEL technique allows the investigation of optically-allowed and forbidden transitions with sufficient energy resolution, typically about 0.2 eV, to resolve resonance structures in the cross sections. Results from the JILA/ORNL MEIBEL experiment on dipole-allowed transitions in several ions demonstrate the success of various theoretical methods in predicting cross sections in the absence of resonances. Comparisons of R-matrix calculations and measured cross sections for spin-forbidden transitions in Mg-like Si{sup 2+} and Ar{sup 6+}, however, show that further refinements to the theory are needed in order to more accurately predict cross sections involving significant contributions from dielectronic resonances and interactions between neighboring resonances. {copyright} {ital 1998 American Institute of Physics.}

  9. Correction of the near threshold behavior of electron collisional excitation cross-sections in the plane-wave Born approximation

    DOE PAGES

    Kilcrease, D. P.; Brookes, S.

    2013-08-19

    The modeling of NLTE plasmas requires the solution of population rate equations to determine the populations of the various atomic levels relevant to a particular problem. The equations require many cross sections for excitation, de-excitation, ionization and recombination. Additionally, a simple and computational fast way to calculate electron collisional excitation cross-sections for ions is by using the plane-wave Born approximation. This is essentially a high-energy approximation and the cross section suffers from the unphysical problem of going to zero near threshold. Various remedies for this problem have been employed with varying degrees of success. We present a correction procedure formore » the Born cross-sections that employs the Elwert–Sommerfeld factor to correct for the use of plane waves instead of Coulomb waves in an attempt to produce a cross-section similar to that from using the more time consuming Coulomb Born approximation. We compare this new approximation with other, often employed correction procedures. Furthermore, we also look at some further modifications to our Born Elwert procedure and its combination with Y.K. Kim's correction of the Coulomb Born approximation for singly charged ions that more accurately approximate convergent close coupling calculations.« less

  10. Correction of the near threshold behavior of electron collisional excitation cross-sections in the plane-wave Born approximation

    NASA Astrophysics Data System (ADS)

    Kilcrease, D. P.; Brookes, S.

    2013-12-01

    The modeling of NLTE plasmas requires the solution of population rate equations to determine the populations of the various atomic levels relevant to a particular problem. The equations require many cross sections for excitation, de-excitation, ionization and recombination. A simple and computational fast way to calculate electron collisional excitation cross-sections for ions is by using the plane-wave Born approximation. This is essentially a high-energy approximation and the cross section suffers from the unphysical problem of going to zero near threshold. Various remedies for this problem have been employed with varying degrees of success. We present a correction procedure for the Born cross-sections that employs the Elwert-Sommerfeld factor to correct for the use of plane waves instead of Coulomb waves in an attempt to produce a cross-section similar to that from using the more time consuming Coulomb Born approximation. We compare this new approximation with other, often employed correction procedures. We also look at some further modifications to our Born Elwert procedure and its combination with Y.K. Kim's correction of the Coulomb Born approximation for singly charged ions that more accurately approximate convergent close coupling calculations.

  11. Correction of the near threshold behavior of electron collisional excitation cross-sections in the plane-wave Born approximation

    SciTech Connect

    Kilcrease, D. P.; Brookes, S.

    2013-08-19

    The modeling of NLTE plasmas requires the solution of population rate equations to determine the populations of the various atomic levels relevant to a particular problem. The equations require many cross sections for excitation, de-excitation, ionization and recombination. Additionally, a simple and computational fast way to calculate electron collisional excitation cross-sections for ions is by using the plane-wave Born approximation. This is essentially a high-energy approximation and the cross section suffers from the unphysical problem of going to zero near threshold. Various remedies for this problem have been employed with varying degrees of success. We present a correction procedure for the Born cross-sections that employs the Elwert–Sommerfeld factor to correct for the use of plane waves instead of Coulomb waves in an attempt to produce a cross-section similar to that from using the more time consuming Coulomb Born approximation. We compare this new approximation with other, often employed correction procedures. Furthermore, we also look at some further modifications to our Born Elwert procedure and its combination with Y.K. Kim's correction of the Coulomb Born approximation for singly charged ions that more accurately approximate convergent close coupling calculations.

  12. High excitation rovibrational molecular analysis in warm environments

    NASA Astrophysics Data System (ADS)

    Zhang, Ziwei; Stancil, Phillip C.; Cumbee, Renata; Ferland, Gary J.

    2017-06-01

    Inspired by advances in infrared observation (e.g., Spitzer, Herschel and ALMA), we investigate rovibrational emission CO and SiO in warm astrophysical environments. With recent innovation in collisional rate coefficients and rescaling methods, we are able to construct more comprehensive collisional data with high rovibrational states (vibration up to v=5 and rotation up to J=40) and multiple colliders (H2, H and He). These comprehensive data sets are used in spectral simulations with the radiative transfer codes RADEX and Cloudy. We obtained line ratio diagnostic plots and line spectra for both near- and far-infrared emission lines over a broad range of density and temperature for the case of a uniform medium. Considering the importance of both molecules in probing conditions and activities of UV-irradiated interstellar gas, we model rovibrational emission in photodissociation region (PDR) and AGB star envelopes (such as VY Canis Majoris, IK Tau and IRC +10216) with Cloudy. Rotational diagrams, energy distribution diagrams, and spectra are produced to examine relative state abundances, line emission intensity, and other properties. With these diverse models, we expect to have a better understanding of PDRs and expand our scope in the chemical architecture and evolution of AGB stars and other UV-irradiated regions. The soon to be launched James Webb Space Telescope (JWST) will provide high resolution observations at near- to mid-infrared wavelengths, which opens a new window to study molecular vibrational emission calling for more detailed chemical modeling and comprehensive laboratory astrophysics data on more molecules. This work was partially supported by NASA grants NNX12AF42G and NNX15AI61G. We thank Benhui Yang, Kyle Walker, Robert Forrey, and N. Balakrishnan for collaborating on the collisional data adopted in the current work.

  13. Polarization of Lyman-Alpha Radiation from Atomic Hydrogen Excited by Electron Impact form Near Threshold to 1800 eV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Slevin, J. A.; Dziczek, D.; McConkey, J. W.; Bray, Igor

    1998-01-01

    The polarization of Lyman-a radiation, produced by electron-impact excitation of atomic hydrogen, has been measured over the extended energy range from near threshold to 1800 eV. Measurements were obtained in a crossed-beam experiment using a silica-reflection linear polarization analyzer in tandem with a vacuum-ultraviolet monochromator to isolate the emitted line radiation. Comparison with various theoretical calculations shows that the present experimental results are in good agreement with theory over the entire range of electron-impact energies and, in particular, are in excellent agreement with theoretical convergent-close-coupling (CCC) calculations performed in the present work. Our polarization data are significantly different from the previous experimental measurements of Ott, Kauppila, and Fite.

  14. Excitation function shape and neutron spectrum of the 7Li(p ,n )7Be reaction near threshold

    NASA Astrophysics Data System (ADS)

    Martín-Hernández, Guido; Mastinu, Pierfrancesco; Maggiore, Mario; Pranovi, Lorenzo; Prete, Gianfranco; Praena, Javier; Capote-Noy, Roberto; Gramegna, Fabiana; Lombardi, Augusto; Maran, Luca; Scian, Carlo; Munaron, Enrico

    2016-09-01

    The forward-emitted low energy tail of the neutron spectrum generated by the 7Li(p ,n )7Be reaction on a thick target at a proton energy of 1893.6 keV was measured by time-of-flight spectroscopy. The measurement was performed at BELINA (Beam Line for Nuclear Astrophysics) of the Laboratori Nazionali di Legnaro. Using the reaction kinematics and the proton on lithium stopping power the shape of the excitation function is calculated from the measured neutron spectrum. Good agreement with two reported measurements was found. Our data, along with the previous measurements, are well reproduced by the Breit-Wigner single-resonance formula for s -wave particles. The differential yield of the reaction is calculated and the widely used neutron spectrum at a proton energy of 1912 keV was reproduced. Possible causes regarding part of the 6.5% discrepancy between the 197Au(n ,γ ) cross section measured at this energy by Ratynski and Kappeler [Phys. Rev. C 37, 595 (1988), 10.1103/PhysRevC.37.595] and the one obtained using the Evaluated Nuclear Data File version B-VII.1 are given.

  15. Ro-vibrational excitation, alignment and orientation distributions of fast non-dissociatively scattered molecules

    NASA Astrophysics Data System (ADS)

    Harder, R.; Snowdon, K. J.

    1997-12-01

    The ro-vibrational distribution of fast diatomic molecules scattered from an uncorrugated surface under strongly dissipative glancing incidence conditions is calculated. The classical trajectory simulation includes potential surface switching associated with hot-electron scattering processes. Both ro-vibrational excitation and strong alignment of the classical angular momentum vector in the surface plane ("cartwheel motion") are observed, independent of the occurrence of potential surface switching. Ro-vibrational excitation is enhanced strongly by transitions between potential surfaces. The resultant larger proportion of molecules in highly rotationally excited states leads to a higher fraction of cartwheel-aligned molecules in the scattered molecule ensemble. The molecules which dissociate in the simulation are characterised by surface normal peaked internuclear axis orientation distributions. This is in agreement with the results of recent experiments [A. Nesbitt et al., Surf. Sci. 331-333 (1995) 321]. We observe, in addition, an enhanced rotational population of "topspin" oriented molecules, which arises from differences in the surface parallel oriented friction forces acting on each atom of the molecule. Glancing incidence scattering from well-prepared close-packed metal surfaces would appear to provide an efficient, general method to obtain a beam of preferentially aligned fast neutral diatomic molecules.

  16. Boltzmann rovibrational collisional coarse-grained model for internal energy excitation and dissociation in hypersonic flows.

    PubMed

    Munafò, A; Panesi, M; Magin, T E

    2014-02-01

    A Boltzmann rovibrational collisional coarse-grained model is proposed to reduce a detailed kinetic mechanism database developed at NASA Ames Research Center for internal energy transfer and dissociation in N(2)-N interactions. The coarse-grained model is constructed by lumping the rovibrational energy levels of the N(2) molecule into energy bins. The population of the levels within each bin is assumed to follow a Boltzmann distribution at the local translational temperature. Excitation and dissociation rate coefficients for the energy bins are obtained by averaging the elementary rate coefficients. The energy bins are treated as separate species, thus allowing for non-Boltzmann distributions of their populations. The proposed coarse-grained model is applied to the study of nonequilibrium flows behind normal shock waves and within converging-diverging nozzles. In both cases, the flow is assumed inviscid and steady. Computational results are compared with those obtained by direct solution of the master equation for the rovibrational collisional model and a more conventional multitemperature model. It is found that the proposed coarse-grained model is able to accurately resolve the nonequilibrium dynamics of internal energy excitation and dissociation-recombination processes with only 20 energy bins. Furthermore, the proposed coarse-grained model provides a superior description of the nonequilibrium phenomena occurring in shock heated and nozzle flows when compared with the conventional multitemperature models.

  17. Inelastic low-energy collisions of electrons with HeH+: Rovibrational excitation and dissociative recombination

    NASA Astrophysics Data System (ADS)

    Čurík, Roman; Greene, Chris H.

    2017-08-01

    Inelastic low-energy (0-1 eV) collisions of electrons with HeH+ cations are treated theoretically, with a focus on the rovibrational excitation and dissociative recombination (DR) channels. In an application of ab initio multichannel quantum defect theory, the description of both processes is based on the Born-Oppenheimer quantum defects. The quantum defects were determined using the R-matrix approach in two different frames of reference: the center-of-charge and the center-of-mass frames. The results obtained in the two reference systems, after implementing the Fano-Jungen style rovibrational frame-transformation technique, show differences in the rate of convergence for these two different frames of reference. We find good agreement with the available theoretically predicted rotationally inelastic thermal rate coefficients. Our computed DR rate also agrees well with the available experimental results. Moreover, several computational experiments shed light on the role of rotational and vibrational excitations in the indirect DR mechanism that governs the low energy HeH+ dissociation process. While the rotational excitation is several orders of magnitude more probable process at the studied collision energies, the closed-channel resonances described by the high-n, rotationally excited neutral molecules of HeH contribute very little to the dissociation probability. But the situation is very different for resonances defined by the high-n, vibrationally excited HeH molecules, which are found to dissociate with approximately 90% probability.

  18. Quantum scattering calculations for ro-vibrational de-excitation of CO by hydrogen atoms

    NASA Astrophysics Data System (ADS)

    Song, Lei; Balakrishnan, N.; van der Avoird, Ad; Karman, Tijs; Groenenboom, Gerrit C.

    2015-05-01

    We present quantum-mechanical scattering calculations for ro-vibrational relaxation of carbon monoxide (CO) in collision with hydrogen atoms. Collisional cross sections of CO ro-vibrational transitions from v = 1, j = 0 - 30 to v' = 0, j' are calculated using the close coupling method for collision energies between 0.1 and 15 000 cm-1 based on the three-dimensional potential energy surface of Song et al. [J. Phys. Chem. A 117, 7571 (2013)]. Cross sections of transitions from v = 1, j ≥ 3 to v' = 0, j' are reported for the first time at this level of theory. Also calculations by the more approximate coupled states and infinite order sudden (IOS) methods are performed in order to test the applicability of these methods to H-CO ro-vibrational inelastic scattering. Vibrational de-excitation rate coefficients of CO (v = 1) are presented for the temperature range from 100 K to 3000 K and are compared with the available experimental and theoretical data. All of these results and additional rate coefficients reported in a forthcoming paper are important for including the effects of H-CO collisions in astrophysical models.

  19. Quantum scattering calculations for ro-vibrational de-excitation of CO by hydrogen atoms

    SciTech Connect

    Song, Lei; Avoird, Ad van der; Karman, Tijs; Groenenboom, Gerrit C.; Balakrishnan, N.

    2015-05-28

    We present quantum-mechanical scattering calculations for ro-vibrational relaxation of carbon monoxide (CO) in collision with hydrogen atoms. Collisional cross sections of CO ro-vibrational transitions from v = 1, j = 0 − 30 to v′ = 0, j′ are calculated using the close coupling method for collision energies between 0.1 and 15 000 cm{sup −1} based on the three-dimensional potential energy surface of Song et al. [J. Phys. Chem. A 117, 7571 (2013)]. Cross sections of transitions from v = 1, j ≥ 3 to v′ = 0, j′ are reported for the first time at this level of theory. Also calculations by the more approximate coupled states and infinite order sudden (IOS) methods are performed in order to test the applicability of these methods to H–CO ro-vibrational inelastic scattering. Vibrational de-excitation rate coefficients of CO (v = 1) are presented for the temperature range from 100 K to 3000 K and are compared with the available experimental and theoretical data. All of these results and additional rate coefficients reported in a forthcoming paper are important for including the effects of H–CO collisions in astrophysical models.

  20. Double Photoionization Near Threshold

    NASA Technical Reports Server (NTRS)

    Wehlitz, Ralf

    2007-01-01

    The threshold region of the double-photoionization cross section is of particular interest because both ejected electrons move slowly in the Coulomb field of the residual ion. Near threshold both electrons have time to interact with each other and with the residual ion. Also, different theoretical models compete to describe the double-photoionization cross section in the threshold region. We have investigated that cross section for lithium and beryllium and have analyzed our data with respect to the latest results in the Coulomb-dipole theory. We find that our data support the idea of a Coulomb-dipole interaction.

  1. Ro-vibrational excitation of SiO by collision with helium at high temperature

    NASA Astrophysics Data System (ADS)

    Balança, Christian; Dayou, Fabrice

    2017-08-01

    We report theoretical rate coefficients for the ro-vibrational excitation of SiO by collision with He. A new, three-dimensional, ab initio potential energy surface, which includes the dependence on the vibrational coordinate of SiO, has been developed for the X1A΄ ground electronic state of the SiO-He system. Quantum dynamics calculations were performed using the vibrational close-coupling rotational infinite order sudden (VCC-IOS) method. Collisional rate coefficients have been determined for the de-excitation of the 41 first rotational states (j = 0-40) of the first six vibrational levels (v = 0-5) of SiO, in the temperature range between 300 and 6000 K. The rotational de-excitation rate coefficients corresponding to the vibrationally elastic process SiO(v, j) → SiO(v, j΄) are found to be almost insensitive to the selected vibrational level. The rate coefficients for the vibrationally inelastic process SiO(v, j) → SiO(v΄, j΄) are significantly enhanced by the kinetic temperature and, to a lesser extent, by the vibrational excitation of SiO, but they are smaller than the vibrationally elastic ones by several orders of magnitude for the whole temperature range. The agreement between the present vibrational close-coupling rotational infinite order sudden (VCC-IOS) results and the available literature data for the SiO-He colliding system is discussed.

  2. Variational calculation of highly excited rovibrational energy levels of H2O2.

    PubMed

    Polyansky, Oleg L; Kozin, Igor N; Ovsyannikov, Roman I; Małyszek, Paweł; Koput, Jacek; Tennyson, Jonathan; Yurchenko, Sergei N

    2013-08-15

    Results are presented for highly accurate ab initio variational calculation of the rotation-vibration energy levels of H2O2 in its electronic ground state. These results use a recently computed potential energy surface and the variational nuclear-motion programs WARV4, which uses an exact kinetic energy operator, and TROVE, which uses a numerical expansion for the kinetic energy. The TROVE calculations are performed for levels with high values of rotational excitation, J up to 35. The purely ab initio calculations of the rovibrational energy levels reproduce the observed levels with a standard deviation of about 1 cm(-1), similar to that of the J = 0 calculation, because the discrepancy between theory and experiment for rotational energies within a given vibrational state is substantially determined by the error in the vibrational band origin. Minor adjustments are made to the ab initio equilibrium geometry and to the height of the torsional barrier. Using these and correcting the band origins using the error in J = 0 states lowers the standard deviation of the observed-calculated energies to only 0.002 cm(-1) for levels up to J = 10 and 0.02 cm(-1) for all experimentally known energy levels, which extend up to J = 35.

  3. Non-Born-Oppenheimer calculations of the rovibrational spectrum of H2 excited to the second rotational level

    NASA Astrophysics Data System (ADS)

    Jones, Keith; Formanek, Martin; Adamowicz, Ludwik

    2017-02-01

    Quantum mechanical, non-relativistic, non-Born-Oppenheimer (non-BO) calculations are performed for the rovibrational spectrum of H2 excited to the second rotational level. The non-BO wave functions of the considered states are expanded in terms of all-particle explicitly correlated Gaussian functions. The dissociation energies and rovibrational transition energies are calculated and compared with experimental values and values obtained in calculations performed by others. The average interparticle distances are calculated and compared with the corresponding values for HD. They show that H2 is a more "diffuse molecule". The nuclear-nuclear correlation functions are calculated and plotted to visualize the "non-BO molecular structure" of H2.

  4. Charge asymmetry in rovibrationally excited HD{sup +} determined using explicitly correlated all-particle Gaussian functions

    SciTech Connect

    Kirnosov, Nikita; Sharkey, Keeper L.; Adamowicz, Ludwik

    2013-11-28

    Very accurate non-Born-Oppenheimer quantum-mechanical calculations are performed to determine the average values of the interparticle distances and the proton-deuteron density function for the rovibrationally excited HD{sup +} ion. The states corresponding to excitations to all bound vibrational states (v = 0, …, 22) and simultaneously excited to the first excited rotational state (N = 1) are considered. To describe each state up to 8000 explicitly correlated all-particle Gaussian functions are used. The nonlinear parameters of the Gaussians are variationally optimized using a procedure that employs the analytical energy gradient determined with respect to these parameters. The results show an increasing asymmetry in the electron distribution with the vibrational excitation as the electron density shifts towards deuteron and away from the proton.

  5. Quantum Scattering Study of Ro-Vibrational Excitations in N+N(sub 2) Collisions under Re-entry Conditions

    NASA Technical Reports Server (NTRS)

    Wang, Dunyou; Stallcop, James R.; Dateo, Christopher E.; Schwenke, David W.; Huo, Winifred M.

    2004-01-01

    A three-dimensional time-dependent quantum dynamics approach using a recently developed ab initio potential energy surface is applied to study ro-vibrational excitation in N+N2 exchange scattering for collision energies in the range 2.1- 3.2 eV. State-to-state integral exchange cross sections are examined to determine the distribution of excited rotational states of N(sub 2). The results demonstrate that highly-excited rotational states are produced by exchange scattering and furthermore, that the maximum value of (Delta)j increases rapidly with increasing collision energies. Integral exchange cross sections and exchange rate constants for excitation to the lower (upsilon = 0-3) vibrational energy levels are presented as a function of the collision energy. Excited-vibrational-state distributions for temperatures at 2,000 K and 10,000 K are included.

  6. Dynamics of Rovibrational Energy Transfer from Excited Molecular - Crossed Beam Studies

    NASA Astrophysics Data System (ADS)

    Du, Hong

    1990-01-01

    Rovibrational inelastic scattering has been studied for the collisions between helium and excited molecular iodine (I_2) in a crossed beam apparatus. I _2 was initially prepared in two vibrational states, upsilon' = 15 and 35, in the B O_{rm u }^ + electronic state. Dispersed single vibrational level fluorescence spectra revealed the vibrational inelastic scattering. The collision energy (Ecm) was varied from 35meV to 190meV. Vibrational state changes up to | Deltaupsilon| = 6 in upsilon' = 35 and | Deltaupsilon| = 3 in upsilon' = 15 were observed. Nearly 200 relative vibrational state-to-state inelastic scattering cross sections were measured. At each Ecm, all the cross sections for both upsilon' = 15 and 35 can be fitted by a single exponential function sigma ~ exp(-| Delta rm E|/beta). At high Ecm, beta_{rm Vto T} is equal to beta_{rm Tto V}. At low ECM, beta _{rm Vto T} is larger than beta_{rm Tto V}. However, all beta's are linear functions of Ecm. Also the cross sections for the Deltaupsilon = +/-1 scattering are nearly independent of Ecm. Considering that the collisions are not adiabatic, these results are not consistent with the well-known Landau-Teller theory. Using the empirical dependence of the cross sections on Ecm, we calculated the thermal rate constants. The calculation at 300K agrees with the bulb experiment for V to T but not for T to V transitions. The calculation also shows that the bulb energy transfer is mainly induced by collisions with velocities ~2 times larger than the most probable velocity. From the cross sections, mean energy transfer per vibrationally inelastic collision, < Deltarm E>, was also obtained. The results show that < Deltarm E> increases linearly with Ecm and levels off to near-zero at high collision energy. At low Ecm, < Deltarm E> in upsilon' = 15 is larger than that in upsilon' = 35. The average rotational energy transfered increases almost linearly with Ecm but is small, only ~ 2% of the Ecm. This is a direct result of

  7. Absolute cross sections for near-threshold electron-impact excitation of the 2s 2S-->2p 2P transition in C3+

    NASA Astrophysics Data System (ADS)

    Bannister, M. E.; Chung, Y.-S.; Djurić, N.; Wallbank, B.; Woitke, O.; Zhou, S.; Dunn, G. H.; Smith, A. C.

    1998-01-01

    Absolute total cross sections for electron-impact excitation of the 2s 2S-->2p 2P transition in C3+ were measured from 7.35 eV to 8.45 eV using the merged electron-ion-beams energy-loss technique. The results settle the discrepancy between two previous experiments using the crossed-beams fluorescence method, being in very good agreement with the older results [P. O. Taylor, D. Gregory, G. H. Dunn, R. A. Phaneuf, and D. H. Crandall, Phys. Rev. Lett. 39, 1256 (1977)] but less so with the more recent ones [D. W. Savin, L. D. Gardner, D. B. Reisenfeld, A. R. Young, and J. L. Kohl, Phys. Rev. A 51, 2162 (1995)]. The present measurements are also in good agreement with unitarized Coulomb-Born and close-coupling calculations.

  8. Atom and molecule emission caused by ion impact into a frozen oxygen target: Role of rovibrational excitation

    NASA Astrophysics Data System (ADS)

    Anders, Christian; Pedrys, Roman; Urbassek, Herbert M.

    2013-11-01

    Translational energy distributions of particles sputtered by 750 eV Ne+ ion impact into a cryogenic O2 target are studied using molecular-dynamics simulation. When comparing the energy distribution of emitted molecules to a Thompson distribution, good agreement can only be found for energies E with Urovibrationally excited molecules after emission. Around 2% of the sputtered particles consist of radicals (atomic O). These originate from direct projectile-molecule collisions; they are emitted early in the collision cascade and feature a strong high-energy contribution.

  9. Quantum optimal control of the isotope-selective rovibrational excitation of diatomic molecules

    NASA Astrophysics Data System (ADS)

    Kurosaki, Yuzuru; Yokoyama, Keiichi

    2017-08-01

    We carry out optimal control theory calculations for isotope-selective pure rotational and vibrational-rotational excitations of diatomic molecules. The fifty-fifty mixture of diatomic isotopologues, 7Li37Cl and 7Li35Cl, is considered and the molecules are irradiated with a control pulse. In the wave packet propagation we employ the method quantum mechanically rigorous for the two-dimensional system including both the radial and angular motions. We investigate quantum controls of the isotope-selective pure rotational excitation for two total times 1280000 and 2560000 a.u. (31.0 and 61.9 ps) and the vibrational-rotational excitation for three total times, 640000, 1280000, and 2560000 a.u. (15.5, 31.0, and 61.9 ps) The initial state is set to the situation that both the isotopologues are in the ground vibrational and rotational levels, v = 0 and J = 0. The target state for pure rotational excitation is set to 7Li37Cl (v = 0, J = 1) and 7Li35Cl (v = 0, J = 0); that for vibrational-rotational excitation is set to 7Li37Cl (v = 1, J = 1) and 7Li35Cl (v = 0, J = 0). The obtained final yields are quite high and those for the longest total time are calculated to be nearly 1.0. When total time is 1280000 a.u., the final yields for the pure rotational excitation are slightly smaller than those for the vibrational-rotational excitation. This is because the isotope shift (difference in transition energy between the two isotopologues) for the pure rotational transition between low-lying levels is much smaller than that for the vibrational-rotational transition. We thus theoretically succeed in controlling the isotope-selective excitations of diatomic molecules using the method including both radial and angular motions quantum mechanically.

  10. Imaging of rotational wave-function in photodissociation of rovibrationally excited HCl molecules

    NASA Astrophysics Data System (ADS)

    Grygoryeva, K.; Rakovský, J.; Votava, O.; Fárník, M.

    2017-07-01

    We demonstrate a visualization of quantum mechanical phenomena with the velocity map imaging (VMI) technique, combining vibrationally mediated photodissociation (VMP) of a simple diatomic HCl with the VMI of its H-photofragments. Free HCl molecules were excited by a pump infrared (IR) laser pulse to particular rotational J levels of the v = 2 vibrational state, and subsequently a probe ultraviolet laser photodissociated the molecule at a fixed wavelength of 243.07 nm where also the H-fragments were ionized. The molecule was aligned by the IR excitation with respect to the IR laser polarization, and this alignment was reflected in the angular distribution of the H-photofragments. In particular, the highest degree of molecular alignment was achieved for the J =1 ←0 transition, which exclusively led to the population of a single rotational state with M = 0. The obtained images were analyzed for further details of the VMP dynamics, and different J states were studied as well. Additionally, we investigated the dynamic evolution of the excited states by changing the pump-probe laser pulse delay; the corresponding images reflected dephasing due to a coupling between the molecular angular momentum and nuclear spin. Our measurements confirmed previous observation using the time-of-flight technique by Sofikitis et al. [J. Chem. Phys. 127, 144307 (2007)]. We observed a partial recovery of the originally excited state after 60 ns in agreement with the previous observation.

  11. Three-photon near-threshold photoionization dynamics of isooctane

    NASA Astrophysics Data System (ADS)

    Healy, Andrew T.; Underwood, David F.; Lipsky, Sanford; Blank, David A.

    2005-08-01

    The electron survival probability following three-photon (9.3eV total) near-threshold photoionization of neat isooctane is measured with sub-50fs time resolution. The measured dynamics are nonexponential in time and are well described by a diffusion-controlled electron-cation recombination model. Excitation-power-dependent studies indicate that the unperturbed three-photon threshold ionization is only observed for pump irradiance below 0.5TW/cm2. At excitation fields above this level, the signal is no longer cubic in the excitation irradiance, and the observed electron survival probability dramatically changes, decaying as a single exponential in time.

  12. Three-photon near-threshold photoionization dynamics of isooctane.

    PubMed

    Healy, Andrew T; Underwood, David F; Lipsky, Sanford; Blank, David A

    2005-08-01

    The electron survival probability following three-photon (9.3 eV total) near-threshold photoionization of neat isooctane is measured with sub-50 fs time resolution. The measured dynamics are nonexponential in time and are well described by a diffusion-controlled electron-cation recombination model. Excitation-power-dependent studies indicate that the unperturbed three-photon threshold ionization is only observed for pump irradiance below 0.5 TW cm2. At excitation fields above this level, the signal is no longer cubic in the excitation irradiance, and the observed electron survival probability dramatically changes, decaying as a single exponential in time.

  13. Detection of rovibrationally excited molecular hydrogen in the electronic ground state via synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Béchu, S.; Aleiferis, S.; Bentounes, J.; Gavilan, L.; Shakhatov, V. A.; Bès, A.; Svarnas, P.; Mazouffre, S.; de Oliviera, N.; Engeln, R.; Lemaire, J. L.

    2017-08-01

    We describe an original setup named SCHEME (Source of exCited HydrogEn MolEcules) designed to study the recombinative desorption mechanisms of H atoms on a surface by means of high-brilliance monochromatic synchrotron radiation (SR). H atoms are produced on electrically heated filaments under vacuum (in the absence of any discharge) and subsequently recombine on a surface to produce excited hydrogen molecules, namely, H2 ( v″, J″ ). Once these levels are produced, they are probed in the vacuum chamber with 5-40 eV (248-31 nm) SR-photons. A preliminary test with Krypton has demonstrated the feasibility of SCHEME to obtain simultaneously VUV-synchrotron radiation induced fluorescence and VUV-absorption signals with room-temperature gas. In order to evaluate the hydrogen molecule dissociation induced by the heated filaments, the absolute density of H atoms has been measured by VUV-absorption. At 1800 K and 100 mTorr, we estimated a dissociation degree of 10-4 , which corresponds to an absolute density of 1.8 ×1017 m-3. VUV-absorption spectroscopy is shown to be a valuable tool to detect H2 ( v″, J″ ) molecules up to v″ = 3. Possible improvements of the experimental setup, to detect higher v″ levels, are suggested in the end of this paper.

  14. Photoproduction of the phi (1020) near threshold

    SciTech Connect

    D.J. Tedeschi; M. Huertas

    2000-05-12

    Photoproduction of phi mesons at photon energies below 2 GeV were measured at the CLAS detector in Hall B of Thomas Jefferson National Accelerator Facility. Preliminary differential cross sections are reported from the proton near threshold. The measurement are extended to the region in the variable t where production mechanisms beyond that of diffraction are expected to become significant.

  15. Near-threshold production of [eta] mesons

    SciTech Connect

    Wilkin, C. )

    1993-03-01

    It is shown that the striking energy variation in the [ital pd][r arrow][sup 3]He [eta] cross section near threshold is probably due to a final state interaction associated with a large (complex) [eta][minus][sup 3]He scattering length. The consequences of this hypothesis are studied for the production of the meson in the [eta][minus][sup 4]He and [eta][minus][sup 7]Be channels.

  16. The high overtone and combination levels of SF6 revisited at Doppler-limited resolution: A global effective rovibrational model for highly excited vibrational states

    NASA Astrophysics Data System (ADS)

    Faye, M.; Boudon, V.; Loëte, M.; Roy, P.; Manceron, L.

    2017-03-01

    Sulfur hexafluoride is an important prototypal molecule for modeling highly excited vibrational energy flow and multi quanta absorption processes in hexafluoride molecules of technological importance. It is also a strong greenhouse gas of anthropogenic origin. This heavy species, however, features many hot bands at room temperature (at which only 30% of the molecules lie in the ground vibrational state), especially those originating from the lowest, v6=1 vibrational state. Using a cryogenic long path cell with variable optical path length and temperatures regulated between 120 and 163 K, coupled to Synchrotron Radiation and a high resolution interferometer, Doppler-limited spectra of the 2ν1 +ν3 , ν1 +ν2 +ν3 , ν1 +ν3 , ν2 +ν3 , 3ν3, ν2 + 3ν3 and ν1 + 3ν3 from 2000 to 4000 cm-1 near-infrared region has been recorded. Low temperature was used to limit the presence of hot bands. The spectrum has been analyzed thanks to the XTDS software package. Combining with previously observed weak difference bands in the far infrared region involving the v1, v2, v3=1 states, we are thus able to use the tensorial model to build a global fit of spectroscopic parameters for v1=1,2, v2=1, v3=1,2,3. The model constitutes a consistent set of molecular parameters and enable spectral rovibrational simulation for all multi-quanta transitions involving v1, v2 and v3 up to v1-3 = 3 . Tests simulation on rovibrational transitions not yet rovibrationally assigned are presented and compared to new experimental data.

  17. The Cascaded Arc: High Flows of Rovibrationally Excited H{sub 2} and its Impact on H{sup -} Ion Formation

    SciTech Connect

    Gabriel, O.; Harskamp, W. E. N. van; Schram, D. C.; Sanden, M. C. M. van de; Engeln, R.

    2009-03-12

    The cascaded arc is a plasma source providing high fluxes of excited and reactive species such as ions, radicals and rovibrationally excited molecules. The plasma is produced under pressures of some kPa in a direct current arc with electrical powers up to 10 kW. The plasma leaves the arc channel through a nozzle and expands with supersonic velocity into a vacuum-chamber kept by pumps at low pressures. We investigated the case of a pure hydrogen plasma jet with and without an applied axial magnetic field that confines ions and electrons in the jet. Highly excited molecules and atoms were detected by means of laser-induced fluorescence and optical emission spectroscopy. In case of an applied magnetic field the atomic state distribution of hydrogen atoms shows an overpopulation between the electronic states p = 5, 4 and 3. The influence of the highly excited hydrogen molecules on H{sup -} ion formation and a possible mechanism involving this negative ion and producing atomic hydrogen in state p = 3 will be discussed.

  18. Resonance effects in near-threshold electron-impact excitation of the 143.4 nm line in the Pb++ ion

    NASA Astrophysics Data System (ADS)

    Gomonai, Anna N.; Hutych, Yuriy I.; Gomonai, Aleksandr I.

    2017-02-01

    Electron-impact excitation of the resonance transition 6 s 26 d 2 D 3/2 → 6 s 26 p 2 P o 1/2 (143.4 nm) in the Pb+ ion within the (6-100) eV energy range is studied spectroscopically using a crossed-beam technique. The observed distinct structure in the energy dependence of the effective excitation cross section (including the energy region above the ion ionization potential) is primarily due to the decay of atomic and ionic autoionizing states, produced mainly by excitation of an electron from the subvalence 5 d 10 shell, to the resonance levels (directly or via the cascade transitions). The absolute cross section value for the line under investigation was determined by normalizing the experimental curve at the electron beam energy of 100 eV to the theoretical data obtained by the Van-Regemorter formula and found to be (0.5 ± 0.3) × 10-16 cm2.

  19. Theoretical resonant electron-impact vibrational excitation, dissociative recombination and dissociative excitation cross sections of ro-vibrationally excited BeH+ ion

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Chakrabarti, K.; Celiberto, R.; Janev, R. K.; Mezei, J. Zs; Niyonzima, S.; Tennyson, J.; Schneider, I. F.

    2017-02-01

    A theoretical study of resonant vibrational excitation, dissociative recombination and dissociative excitation processes of the beryllium monohydride cation, BeH+, induced by electron impact, is reported. Full sets of ro-vibrationally-resolved cross sections and of the corresponding Maxwellian rate coefficients are presented for the three processes. Particular emphasis is given to the high-energy behaviour. Potential curves of {}2{{{Σ }}}+, {}2{{\\Pi }} and {}2{{Δ }} symmetries and the corresponding resonance widths, obtained from R-matrix calculations, provide the input for calculations which use a local complex-potential model for resonant collisions in each of the three symmetries. Rotational motion of nuclei and isotopic effects are also discussed. The relevant results are compared with those obtained using a multichannel quantum defect theory method. Full results are available from the Phys4Entry database.

  20. Intrashell Electron Interaction Mediated Photoformation of Hollow Atoms near Threshold

    SciTech Connect

    Houtari, S.; Kao, C.; Hamalainen, K.; Diamant, R.; Sharon, R.; Deutsch, M.

    2008-07-25

    Double photoionization (DPI) of an atom by a single photon is a direct consequence of electron-electron interactions within the atom. We have measured the evolution of the K-shell DPI from threshold up in transition metals by high-resolution x-ray emission spectroscopy of the K{sup h}a hypersatellites, photoexcited by monochromatized synchrotron radiation. The measured evolution of the single-to-double photoionization cross-section ratio with excitation energy was found to be universal. Theoretical fits suggest that near threshold DPI is predominantly a semiclassical knockout effect, rather than the purely quantum-mechanical shake-off observed at the infinite photon energy limit.

  1. Near-threshold laser sputting of gold

    NASA Astrophysics Data System (ADS)

    Bennett, Ted D.; Grigoropoulos, Costas P.; Krajnovich, Douglas J.

    1995-01-01

    This work characterizes the laser sputtering of gold by 248 nm laser pulses at near-threshold fluences (material removal rates equal to or less than 10 A/pulse) using time-of-flight plume diagnostics, scanning electron microscope analysis of the surface topography, and thermal analysis of the transient near surface conditions. Pulsed laser irradiation leads to development of surface topography characterized by droplet and ridge formations, and to the liberation of micrometer-sized droplets into the plume. The development of surface topography has been identified with a hydrodynamic response to phase change occuring at the surface of the target. Drawing upon a Rayleigh-Taylor instability description of the melt surface, the readily observable approx. 5 micrometers periodicity in topography formation can be theoretically predicted. Additionally, the preferential formation and liberation of approx. 1 micrometer diameter droplets at the target surface is observed. Nevertheless, the majority of sputtered mass flux is not comprised of droplets, but of neutral gold atoms with almost perfect Bolzmann translational energy distribution. The mean translational energy of the gold atoms, however, is much too high to reconcile with a simple thermal vaporization model. The yield, translational energy, and angular characteristics of the plume are strongly influenced by the surface topography. Local variations in the light absorption and heat transfer explain the qualitative trends in the experimental results.

  2. Near Threshold Pion Electroproduction at High Q^2

    NASA Astrophysics Data System (ADS)

    Khetarpal, Puneet

    2010-02-01

    Near threshold pion electroproduction as a function of Q^2 can be written in terms of new form factors. These new generalized form factors G1^πN and G2^πN have been predicted using light cone sum rules in the chiral limit for the reactions ep ->eNπ in the Q^2 1-10 GeV^2 range. It's an experiment at Jefferson Lab that has been conducted using the CLAS spectrometer to measure near threshold pion electroproduction as a function of Q^2. The differential cross sections and the extracted electromagnetic multipoles and form factors will be presented. )

  3. Near Threshold Neutral Pion Electroproduction at High Momentum Transfers

    NASA Astrophysics Data System (ADS)

    Khetarpal, P.

    2011-02-01

    Near threshold pion electroproduction as a function of Q2 can be written in terms of new form factors. These new generalized form factors G1{π N} and G2{π N} have been predicted using light cone sum rules in the chiral limit for the reactions ep → eNπ in the Q2 1-10 GeV2 range. An experiment at Jefferson Lab has been conducted using the CLAS spectrometer to measure near threshold neutral pion electroproduction as a function of Q2. Preliminary cross sections, S-wave multipoles and generalized form factors are presented.

  4. Is the Aliev and Watson method a suitable tool to relate DK0 of symmetric top molecules to excited state rovibrational parameters?

    NASA Astrophysics Data System (ADS)

    Graner, Georges; Bürger, Hans

    1986-02-01

    The M. R. Aliev and J. K. G. Watson sum rule [ J. Mol. Spectrosc.75, 150-160 (1979)] has been tentatively applied to the following symmetric top molecules: H 3SiCl, H 3GeCl, H 3GeBr, H 3SiF, H 3CCl, D 3CCl, H 3CBr, D 3CBr, H 3CI, D 3CI, H 3CF, D 3CF, NH 3, PH 3, PD 3, AsH 3, H 3CD, H 3SiD, H 3GeD, HCF 3, H 2CCCH 2, and D 2CCCD 2. This sum rule relates ηtJ and ηtK to the quartic centrifugal distortions and should allow the determination of DK0. Therefore we have collected the best available values of the experimental quantities ηtJ and u t = D K0 - {1}/{4} η tK for each perpendicular band. We find that the sum role or its simplified version usually provides estimates which are at least as good as force field predictions of DK0 for which a direct determination is frequently precluded. Since this method is based on the rovibrational analysis of all perpendicular bands, it is also useful to detect perturbations not accounted for in the rovibrational analysis of these fundamentals. In such cases, DK0 values from different sources turn out to be inconsistent. A critical evaluation of the signs and magnitudes of the ηtJ and ηtK values may be helpful to find the origin for such inconsistencies. Because of the greater difficulties met and correlation of parameters usually found in the rovibrational analysis of the light ( XY3) and/or nearly spherical top molecules, the Aliev and Watson sum rule appears at the moment to be of greater value for molecules with a large {A 0}/{B 0} ratio.

  5. Calculating rovibrationally excited states of H2D+ and HD2+ by combination of fixed node and multi-state rotational diffusion Monte Carlo

    NASA Astrophysics Data System (ADS)

    Ford, Jason E.; McCoy, Anne B.

    2016-02-01

    In this work the efficacy of a combined approach for capturing rovibrational coupling is investigated. Specifically, the multi-state rotational DMC method is used in combination with fixed-node DMC in a study of the rotation vibration energy levels of H2D+ and HD2+. Analysis of the results of these calculations shows very good agreement between the calculated energies and previously reported values. Where differences are found, they can be attributed to Coriolis couplings, which are large in these ions and which are not fully accounted for in this approach.

  6. Near-Threshold Meson Production in pp Collisions

    NASA Astrophysics Data System (ADS)

    Bedfer, Yann

    1998-11-01

    A program of near threshold investigations of meson production channels in vec p + p collisions has been carried out by the DISTO collaboration. Preliminary results are given. The ability of the experimental apparatus to eventually determine total and differential cross-sections is demonstrated. A number a spin observables will also be evaluated. The potentialities of these measurements for the understanding of two leading problems in meson physics: OZI rule violation in φ production and status of the η ' meson, are discussed.

  7. Intrashell Electron-Interaction-Mediated Photoformation of Hollow Atoms near Threshold

    NASA Astrophysics Data System (ADS)

    Huotari, S.; Hämäläinen, K.; Diamant, R.; Sharon, R.; Kao, C. C.; Deutsch, M.

    2008-07-01

    Double photoionization (DPI) of an atom by a single photon is a direct consequence of electron-electron interactions within the atom. We have measured the evolution of the K-shell DPI from threshold up in transition metals by high-resolution x-ray emission spectroscopy of the Khα hypersatellites, photoexcited by monochromatized synchrotron radiation. The measured evolution of the single-to-double photoionization cross-section ratio with excitation energy was found to be universal. Theoretical fits suggest that near threshold DPI is predominantly a semiclassical knockout effect, rather than the purely quantum-mechanical shake-off observed at the infinite photon energy limit.

  8. Poisson distribution to analyze near-threshold motor evoked potentials.

    PubMed

    Kaelin-Lang, Alain; Conforto, Adriana B; Z'Graggen, Werner; Hess, Christian W

    2010-11-01

    Motor unit action potentials (MUAPs) evoked by repetitive, low-intensity transcranial magnetic stimulation can be modeled as a Poisson process. A mathematical consequence of such a model is that the ratio of the variance to the mean of the amplitudes of motor evoked potentials (MEPs) should provide an estimate of the mean size of the individual MUAPs that summate to generate each MEP. We found that this is, in fact, the case. Our finding thus supports the use of the Poisson distribution to model MEP generation and indicates that this model enables characterization of the motor unit population that contributes to near-threshold MEPs.

  9. A Survey of Architectural Techniques for Near-Threshold Computing

    SciTech Connect

    Mittal, Sparsh

    2015-12-28

    Energy efficiency has now become the primary obstacle in scaling the performance of all classes of computing systems. In low-voltage computing and specifically, near-threshold voltage computing (NTC), which involves operating the transistor very close to and yet above its threshold voltage, holds the promise of providing many-fold improvement in energy efficiency. However, use of NTC also presents several challenges such as increased parametric variation, failure rate and performance loss etc. Our paper surveys several re- cent techniques which aim to offset these challenges for fully leveraging the potential of NTC. By classifying these techniques along several dimensions, we also highlight their similarities and differences. Ultimately, we hope that this paper will provide insights into state-of-art NTC techniques to researchers and system-designers and inspire further research in this field.

  10. On thermal corrections to near-threshold annihilation

    NASA Astrophysics Data System (ADS)

    Kim, Seyong; Laine, M.

    2017-01-01

    We consider non-relativistic ``dark'' particles interacting through gauge boson exchange. At finite temperature, gauge exchange is modified in many ways: virtual corrections lead to Debye screening; real corrections amount to frequent scatterings of the heavy particles on light plasma constituents; mixing angles change. In a certain temperature and energy range, these effects are of order unity. Taking them into account in a resummed form, we estimate the near-threshold spectrum of kinetically equilibrated annihilating TeV scale particles. Weakly bound states are shown to "melt" below freeze-out, whereas with attractive strong interactions, relevant e.g. for gluinos, bound states boost the annihilation rate by a factor 04... 8 with respect to the Sommerfeld estimate, thereby perhaps helping to avoid overclosure of the universe. Modestly non-degenerate dark sector masses and a way to combine the contributions of channels with different gauge and spin structures are also discussed.

  11. A Survey of Architectural Techniques for Near-Threshold Computing

    DOE PAGES

    Mittal, Sparsh

    2015-12-28

    Energy efficiency has now become the primary obstacle in scaling the performance of all classes of computing systems. In low-voltage computing and specifically, near-threshold voltage computing (NTC), which involves operating the transistor very close to and yet above its threshold voltage, holds the promise of providing many-fold improvement in energy efficiency. However, use of NTC also presents several challenges such as increased parametric variation, failure rate and performance loss etc. Our paper surveys several re- cent techniques which aim to offset these challenges for fully leveraging the potential of NTC. By classifying these techniques along several dimensions, we also highlightmore » their similarities and differences. Ultimately, we hope that this paper will provide insights into state-of-art NTC techniques to researchers and system-designers and inspire further research in this field.« less

  12. Near-threshold photoproduction of Φ mesons from deuterium

    DOE PAGES

    Qian, X.; Chen, W.; Gao, H.; ...

    2011-01-05

    In this report, we measure the differential cross section onmore » $$\\phi$$-meson photoproduction from deuterium near the production threshold for a proton using the CLAS detector and a tagged-photon beam in Hall B at Jefferson Lab. The measurement was carried out by a triple coincidence detection of a proton, $K^+$ and $K^-$ near the theoretical production threshold of 1.57 GeV. Moreover, the extracted differential cross sections $$\\frac{d\\sigma}{dt}$$ for the initial photon energy from 1.65-1.75 GeV are consistent with predictions based on a quasifree mechanism. Ultimately, this experiment establishes a baseline for a future experimental search for an exotic $$\\phi$$-N bound state from heavier nuclear targets utilizing subthreshold/near-threshold production of $$\\phi$$ mesons.« less

  13. Photoproduction of the phi (1020) near threshold in CLAS

    SciTech Connect

    Tedeschi, D J

    2002-06-01

    The differential cross section for the photoproduction of the phi(1020) near threshold (E_{gamma} - 1.57GeV ) is predicted to be sensitive to production mechanisms other than diffraction. However, the existing low energy data is of limited statistics and kinematical coverage. Complete measurements of phi meson production on the proton have been performed at the Thomas Jefferson National Accelerator Facility using a liquid hydrogen target and the CEBAF Large Acceptance Spectrometer (CLAS). The phi was identified by missing mass using a proton and positive kaon detected by CLAS in coincidence with an electron in the photon tagger. The energy of the tagged, bremsstrahlung photons ranged from phi-threshold to 2.4 GeV. A description of the data set and the differential cross section far (E_{gamma} = 2.0 GeV ) will be presented and compared with present theoretical calculations.

  14. Near-threshold photoproduction of Φ mesons from deuterium

    SciTech Connect

    Qian, X.; Chen, W.; Gao, H.; Hicks, K.; Kramer, K.; Laget, J. M.; Mibe, T.; Qiang, Y.; Stepanyan, S.; Tedeschi, D. J.; Xu, W.; Adhikari, K. P.; Amaryan, M.; Anghinolfi, M.; Ball, J.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Bellis, M.; Biselli, A. S.; Bookwalter, C.; Branford, D.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Careccia, S. L.; Carman, D. S.; Cole, P. L.; Collins, P.; Crede, V.; D'Angelo, A.; Daniel, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Dey, B.; Dhamija, S.; Djalali, C.; Doughty, D.; Dupre, R.; Egiyan, H.; El Alaoui, A.; Eugenio, P.; Fegan, S.; Gabrielyan, M. Y.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Gothe, R. W.; Graham, L.; Griffioen, K. A.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Hassall, N.; Holtrop, M.; Ilieva, Y.; Ireland, D. G.; Jawalkar, S. S.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Khetarpal, P.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Konczykowski, P.; Kubarovsky, V.; Kuleshov, S. V.; Kuznetsov, V.; Livingston, K.; Martinez, D.; Mayer, M.; McAndrew, J.; McCracken, M. E.; McKinnon, B.; Meyer, C. A.; Mikhailov, K.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Moreno, B.; Moriya, K.; Morrison, B.; Moutarde, H.; Munevar, E.; Nadel-Turonski, P.; Ni, A.; Niccolai, S.; Niculescu, I.; Niroula, M. R.; Osipenko, M.; Ostrovidov, A. I.; Paremuzyan, R.; Park, K.; Park, S.; Pereira, S. Anefalos; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Ricco, G.; Ripani, M.; Ritchie, B. G.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M. S.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Seraydaryan, H.; Sharabian, Y. G.; Smith, E. S.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S. S.; Stoler, P.; Strakovsky, I. I.; Strauch, S.; Taiuti, M.; Taylor, C. E.; Tkachenko, S.; Ungaro, M.; Vernarsky, B.; Vineyard, M. F.; Voutier, E.; Weinstein, L. B.; Weygand, D. P.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, B.; Zhao, Z. W.

    2011-01-05

    In this report, we measure the differential cross section on $\\phi$-meson photoproduction from deuterium near the production threshold for a proton using the CLAS detector and a tagged-photon beam in Hall B at Jefferson Lab. The measurement was carried out by a triple coincidence detection of a proton, $K^+$ and $K^-$ near the theoretical production threshold of 1.57 GeV. Moreover, the extracted differential cross sections $\\frac{d\\sigma}{dt}$ for the initial photon energy from 1.65-1.75 GeV are consistent with predictions based on a quasifree mechanism. Ultimately, this experiment establishes a baseline for a future experimental search for an exotic $\\phi$-N bound state from heavier nuclear targets utilizing subthreshold/near-threshold production of $\\phi$ mesons.

  15. Triple photoionization of Ne and Ar near threshold

    SciTech Connect

    Bluett, J.B.; Wehlitz, R.; Lukic, D.

    2004-04-01

    The triple-photoionization cross section of neon and argon near threshold has been investigated by ion time-of-flight spectrometry. We applied the Wannier power law to our data and confirmed the theoretical Wannier exponent in the cases of Ne and Ar. Our data also agree with previous findings regarding the Wannier exponent and its range of validity for Ne. However, the Wannier power law exhibits a much smaller range of validity of 2 eV for Ar compared to 5 eV for Ne. Also, in contrast to a previous experiment, we do not find a 'second' power law but a gradual decrease of the exponent above the range of validity of the Wannier power law.

  16. Near-threshold femtosecond laser fabrication of one-dimensional subwavelength nanogratings on a graphite surface

    NASA Astrophysics Data System (ADS)

    Golosov, E. V.; Ionin, A. A.; Kolobov, Yu. R.; Kudryashov, S. I.; Ligachev, A. E.; Makarov, S. V.; Novoselov, Yu. N.; Seleznev, L. V.; Sinitsyn, D. V.; Sharipov, A. R.

    2011-03-01

    Superimposed one-dimensional quasiperiodic gratings with multiple periods Λ ≈ 110-800 nm well below or comparable to the pump laser wavelength of 744 nm, and ridge orientations perpendicular to the linear polarization of infrared femtosecond laser pulses, were fabricated after multiple near-threshold laser shots on a planar surface of quasimonocrystalline graphite in ambient air. The broad range of the grating periods corresponds to the large number of spatial Fourier harmonics of the final nanorelief (up to m=7th order, Λm≈800 nm/m=110-800 nm), qualitatively representing the nonsinusoidal profile of the laser-induced intermediate surface relief (the set of periodic, broadly spaced narrow nanotrenches), which provides the corresponding multiangle diffraction of the incident femtosecond laser pulses. Experimental measurements and modeling of the transient optical constants of the photoexcited graphite justify the excitation, at the first stage, of the first-order (Λ1≈800 nm) surface plasmon-polaritonic (SPP) wave on the photo-excited initial planar graphite surface becoming metallic via photo-generation of dense electron hole plasma (˜1021 cm-3). Such an SPP wave provides intermediate nanorelief in the form of the nonsinusoidal surface grating via its interference with the incident laser wave, resulting under near-threshold laser irradiation conditions in the highly localized surface ablation of the material in the interference maxima. During the next stage, the multiperiod subwavelength nanogratings develop through the multiangle diffraction of the multiple incident laser pulses on the intermediate nonsinusoidal surface grating.

  17. Detection of Near-Threshold Sounds is Independent of EEG Phase in Common Frequency Bands

    PubMed Central

    Zoefel, Benedikt; Heil, Peter

    2013-01-01

    Low-frequency oscillations in the electroencephalogram (EEG) are thought to reflect periodic excitability changes of large neural networks. Consistent with this notion, detection probability of near-threshold somatosensory, visual, and auditory targets has been reported to co-vary with the phase of oscillations in the EEG. In audition, entrainment of δ-oscillations to the periodic occurrence of sounds has been suggested to function as a mechanism of attentional selection. Here, we examine in humans whether the detection of brief near-threshold sounds in quiet depends on the phase of EEG oscillations. When stimuli were presented at irregular intervals, we did not find a systematic relationship between detection probability and phase. When stimuli were presented at regular intervals (2-s), reaction times were significantly shorter and we observed phase entrainment of EEG oscillations corresponding to the frequency of stimulus presentation (0.5 Hz), revealing an adjustment of the system to the regular stimulation. The amplitude of the entrained oscillation was higher for hits than for misses, suggesting a link between entrainment and stimulus detection. However, detection was independent of phase at frequencies ≥1 Hz. Furthermore, we show that when the data are analyzed using acausal, though common, algorithms, an apparent “entrainment” of the δ-phase to presented stimuli emerges and detection probability appears to depend on δ-phase, similar to reports in the literature. We show that these effects are artifacts from phase distortion at stimulus onset by contamination with the event-related potential, which differs markedly for hits and misses. This highlights the need to carefully deal with this common problem, since otherwise it might bias and mislead this exciting field of research. PMID:23717293

  18. Detection of Near-Threshold Sounds is Independent of EEG Phase in Common Frequency Bands.

    PubMed

    Zoefel, Benedikt; Heil, Peter

    2013-01-01

    Low-frequency oscillations in the electroencephalogram (EEG) are thought to reflect periodic excitability changes of large neural networks. Consistent with this notion, detection probability of near-threshold somatosensory, visual, and auditory targets has been reported to co-vary with the phase of oscillations in the EEG. In audition, entrainment of δ-oscillations to the periodic occurrence of sounds has been suggested to function as a mechanism of attentional selection. Here, we examine in humans whether the detection of brief near-threshold sounds in quiet depends on the phase of EEG oscillations. When stimuli were presented at irregular intervals, we did not find a systematic relationship between detection probability and phase. When stimuli were presented at regular intervals (2-s), reaction times were significantly shorter and we observed phase entrainment of EEG oscillations corresponding to the frequency of stimulus presentation (0.5 Hz), revealing an adjustment of the system to the regular stimulation. The amplitude of the entrained oscillation was higher for hits than for misses, suggesting a link between entrainment and stimulus detection. However, detection was independent of phase at frequencies ≥1 Hz. Furthermore, we show that when the data are analyzed using acausal, though common, algorithms, an apparent "entrainment" of the δ-phase to presented stimuli emerges and detection probability appears to depend on δ-phase, similar to reports in the literature. We show that these effects are artifacts from phase distortion at stimulus onset by contamination with the event-related potential, which differs markedly for hits and misses. This highlights the need to carefully deal with this common problem, since otherwise it might bias and mislead this exciting field of research.

  19. Near threshold two meson production in hardonic fusion reactions

    NASA Astrophysics Data System (ADS)

    Jahn, Rainer

    1991-04-01

    An approved and funded exclusive COSY experiment is presented, which focuses on near threshold two meson production via the reactions p+d→3 He+π+π- and p+d→3 He+K+K-. It takes advantage of the high quality of the cooled external COSY beam and the existing spectrometer BIG KARL. The setup consists of a vertex wall and a scintillator cylinder and endcap covering a 4π solid angle. The large efficiency and high resolution of this detection method will yield precision data on the low energy (T<50 MeV) meson-meson interaction and probe into questions like the ABC-effect and KḲ molecule. The detector further allows a measurement of possible radiative φ (1020) decay, which will directly probe the strange quark content of the f0(975). Existing inclusive data as well as first results of a very recent `semi-exclusive' experiment performed at SATURNE will be also be presented.

  20. Pair production near threshold in pulsar magnetic fields

    NASA Technical Reports Server (NTRS)

    Harding, A. K.; Daugherty, J. K.

    1983-01-01

    In Pulsar polar cap models, curvature radiation gamma-rays produce e(+) e(-) pairs in the strong magnetic fields near the surface of the neutron star. While these gamma rays havea energies E sub gamma mc(2), they also propagate at very small angies to the fields, such that the threshold condition, E gamma 2mc(2)/sin theta is just barely satisfied when they pair produce. Threshold effects on the pair production attenuation coefficient, which are due to the discreteness of the e(+) e(-) Landau states, must therefore be considered when computing the mean free paths of curvature radiation photons in pulsar magnetic fields. These effects, which are not incorporated in the asymptotic expression for the attenuation coefficient, have some interesting consequences for pulsar models. Since pair production is suppressed near threshold, the photon mean free paths are longer than previously thought. In magnetic fields greater than approximately 6 x 10 to the 12th G, the pairs tend to be produced in the ground state Landau level and will not synchrotron radiate. Since synchrotron radiation is an essential ingredient in the eiectromagnetic cascades which produce low energy pairs above the acceleration region, pulsars with very high magnetic fields may not produce many pairs.

  1. Near-threshold photodetachment of heavy alkali-metal anions

    SciTech Connect

    Bahrim, C.; Thumm, U.; Khuskivadze, A.A.; Fabrikant, I.I.

    2002-11-01

    We calculate near-threshold photodetachment cross sections for Rb{sup -}, Cs{sup -}, and Fr{sup -} using the Pauli equation method with a model potential describing the effective electron-atom interaction. Parameters of the model potential are fitted to reproduce ab initio scattering phase shifts obtained from Dirac R-matrix calculations. Special care is taken to formulate the boundary conditions near the atomic nucleus for solving the Pauli equation, based on the analytic solution of the Dirac equation for a Coulomb potential. We find a {sup 3}P{sub 1}{sup o} resonance contribution to the photodetachment cross section of Rb{sup -}, Cs{sup -}, and Fr{sup -} ions. Our calculated total photodetachment cross sections for Cs agree with experiments after tuning the resonance position by 2.4 meV. For Rb{sup -} and Fr{sup -} the resonance contribution is much smaller than for Cs. We therefore also provide angle-differential cross sections and asymmetry parameters which are much more sensitive to the resonant contribution than total cross sections.

  2. Accurate calculations of bound rovibrational states for argon trimer

    NASA Astrophysics Data System (ADS)

    Brandon, Drew; Poirier, Bill

    2014-07-01

    This work presents a comprehensive quantum dynamics calculation of the bound rovibrational eigenstates of argon trimer (Ar3), using the ScalIT suite of parallel codes. The Ar3 rovibrational energy levels are computed to a very high level of accuracy (10-3 cm-1 or better), and up to the highest rotational and vibrational excitations for which bound states exist. For many of these rovibrational states, wavefunctions are also computed. Rare gas clusters such as Ar3 are interesting because the interatomic interactions manifest through long-range van der Waals forces, rather than through covalent chemical bonding. As a consequence, they exhibit strong Coriolis coupling between the rotational and vibrational degrees of freedom, as well as highly delocalized states, all of which renders accurate quantum dynamical calculation difficult. Moreover, with its (comparatively) deep potential well and heavy masses, Ar3 is an especially challenging rare gas trimer case. There are a great many rovibrational eigenstates to compute, and a very high density of states. Consequently, very few previous rovibrational state calculations for Ar3 may be found in the current literature—and only for the lowest-lying rotational excitations.

  3. Accurate calculations of bound rovibrational states for argon trimer

    SciTech Connect

    Brandon, Drew; Poirier, Bill

    2014-07-21

    This work presents a comprehensive quantum dynamics calculation of the bound rovibrational eigenstates of argon trimer (Ar{sub 3}), using the ScalIT suite of parallel codes. The Ar{sub 3} rovibrational energy levels are computed to a very high level of accuracy (10{sup −3} cm{sup −1} or better), and up to the highest rotational and vibrational excitations for which bound states exist. For many of these rovibrational states, wavefunctions are also computed. Rare gas clusters such as Ar{sub 3} are interesting because the interatomic interactions manifest through long-range van der Waals forces, rather than through covalent chemical bonding. As a consequence, they exhibit strong Coriolis coupling between the rotational and vibrational degrees of freedom, as well as highly delocalized states, all of which renders accurate quantum dynamical calculation difficult. Moreover, with its (comparatively) deep potential well and heavy masses, Ar{sub 3} is an especially challenging rare gas trimer case. There are a great many rovibrational eigenstates to compute, and a very high density of states. Consequently, very few previous rovibrational state calculations for Ar{sub 3} may be found in the current literature—and only for the lowest-lying rotational excitations.

  4. Rovibrational cooling of molecules by optical pumping.

    PubMed

    Manai, I; Horchani, R; Lignier, H; Pillet, P; Comparat, D; Fioretti, A; Allegrini, M

    2012-11-02

    We demonstrate rotational and vibrational cooling of cesium dimers by optical pumping techniques. We use two laser sources exciting all the populated rovibrational states, except a target state that thus behaves like a dark state where molecules pile up thanks to absorption-spontaneous emission cycles. We are able to accumulate photoassociated cold Cs(2) molecules in their absolute ground state (v = 0, J = 0) with up to 40% efficiency. Given its simplicity, the method could be extended to other molecules and molecular beams. It also opens up general perspectives in laser cooling the external degrees of freedom of molecules.

  5. A Near-Threshold Shape Resonance in the Valence-Shell Photoabsorption of Linear Alkynes

    SciTech Connect

    Jacovella, U.; Holland, D. M. P.; Boye-Peronne, S; Gans, B.; de Oliveira, N; Ito, K; Joyeux, D; Archer, L E; Lucchese, R. R.; Xu, Hong; Pratt, S. T.

    2015-12-17

    The room-temperature photoabsorption spectra of a number of linear alkynes with internal triple bonds (e.g., 2-butyne, 2-pentyne, and 2- and 3-hexyne) show similar resonances just above the lowest ionization threshold of the neutral molecules. These features result in a substantial enhancement of the photoabsorption cross sections relative to the cross sections of alkynes with terminal triple bonds (e.g., propyne, 1-butyne, 1-pentyne,...). Based on earlier work on 2-butyne [Xu et al., J. Chem. Phys. 2012, 136, 154303], these features are assigned to excitation from the neutral highest occupied molecular orbital (HOMO) to a shape resonance with g (l = 4) character and approximate pi symmetry. This generic behavior results from the similarity of the HOMOs in all internal alkynes, as well as the similarity of the corresponding g pi virtual orbital in the continuum. Theoretical calculations of the absorption spectrum above the ionization threshold for the 2- and 3-alkynes show the presence of a shape resonance when the coupling between the two degenerate or nearly degenerate pi channels is included, with a dominant contribution from l = 4. These calculations thus confirm the qualitative arguments for the importance of the l = 4 continuum near threshold for internal alkynes, which should also apply to other linear internal alkynes and alkynyl radicals. The 1-alkynes do not have such high partial waves present in the shape resonance. The lower l partial waves in these systems are consistent with the broader features observed in the corresponding spectra.

  6. Accelerated Near-Threshold Fatigue Crack Growth Behavior of an Aluminum Powder Metallurgy Alloy

    NASA Technical Reports Server (NTRS)

    Piascik, Robert S.; Newman, John A.

    2002-01-01

    Fatigue crack growth (FCG) research conducted in the near threshold regime has identified a room temperature creep crack growth damage mechanism for a fine grain powder metallurgy (PM) aluminum alloy (8009). At very low DK, an abrupt acceleration in room temperature FCG rate occurs at high stress ratio (R = Kmin/Kmax). The near threshold accelerated FCG rates are exacerbated by increased levels of Kmax (Kmax less than 0.4 KIC). Detailed fractographic analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near threshold and Kmax influenced accelerated crack growth is time and temperature dependent.

  7. Near-threshold J/ ψ-meson photoproduction on nuclei

    NASA Astrophysics Data System (ADS)

    Paryev, E. Ya.; Kiselev, Yu. T.

    2017-01-01

    On the basis of the first-collision model that relies on the nuclear spectral function and which includes incoherent processes involving charmonium production in proton-nucleon collisions, the photoproduction of J/ ψ mesons on nuclei is considered at energies close to the threshold for their production on a nucleon. The absorption of final J/ ψ mesons, their formation length, and the binding and Fermi motion of target nucleons are taken into account in this model along with the effect of the nuclear potential on these processes. The A dependences of the absolute and relative charmonium yields are calculated together with absolute and relative excitation functions under various assumptions on the magnitude of the cross section for J/ ψN absorption, the J/ ψ-meson formation length, and their inmedium modification. It is shown that, at energies above the threshold, these features are virtually independent of the formation length and the change in the J/ ψ-meson mass in nuclear matter but are rather highly sensitive to the cross section for J/ ψN interaction. The calculations performed in the present study can be used to determine the unknown cross section for J/ ψ-meson absorption in nuclei from a comparison of their results with data expected from experiments in the Hall C of the CEBAF (USA) facility upgraded to the energy of 12 GeV. It is also shown that the absolute and relative excitation functions for J/ ψ mesons in photon-nucleus reactions at subthreshold energies are sensitive to the change in the meson mass and, hence, carry information about the properties of charmonium in nuclear matter.

  8. Critical nonlinear phenomena for kinetic instabilities near threshold

    SciTech Connect

    Breizman, B.N.; Berk, H.L.; Pekker, M.S.; Porcelli, F.; Stupakov, G.V.; Wong, K.L.

    1997-05-01

    A universal integral equation has been derived and solved for the nonlinear evolution of collective modes driven by kinetic wave particle resonances just above the threshold for instability. The dominant nonlinearity stems from the dynamics of resonant particles that can be treated perturbatively near the marginal state of the system. With a resonant particle source and classical relaxation processes included, the new equation allows the determination of conditions for a soft nonlinear regime, where the saturation level is proportional to the increment above threshold, or a hard nonlinear regime, characterized by explosive behavior, where the saturation level is independent of the closeness to threshold. In the hard regime, rapid oscillations typically arise that lead to large frequency shifts in a fully developed nonlinear stage. The universality of the approach suggests that the theory applies to many types of resonant particle driven instabilities, and several specific cases, viz. energetic particle driven Alfv{acute e}n wave excitation, the fishbone oscillation, and a collective mode in particle accelerators, are discussed. {copyright} {ital 1997 American Institute of Physics.}

  9. Critical nonlinear phenomena for kinetic instabilities near threshold

    SciTech Connect

    Breizman, B.N.; Berk, H.L.; Pekker, M.S.; Porcelli, F.; Stupakov, G.V.; Wong, K.L.

    1996-12-01

    A universal integral equation has been derived and solved for the nonlinear evolution of collective modes driven by kinetic wave particle resonances just above the threshold for instability. The dominant nonlinearity stems from the dynamics of resonant particles which can be treated perturbatively near the marginal state of the system. With a resonant particle source and classical relaxation processes included, the new equation allows the determination of conditions for a soft nonlinear regime, where the saturation level is proportional to the increment above threshold, or a hard nonlinear regime, where the saturation level is independent of the closeness to threshold. It has been found, both analytically and numerically, that in the hard regime the system exhibits explosive behavior and rapid oscillations of the mode amplitude. When the kinetic response is a requirement for the existence of the mode, this explosive behavior is accompanied by frequency chirping. The universality of the approach suggests that the theory applies to many types of resonant particle driven instabilities, and several specific cases, viz. energetic particle driven Alfven wave excitation, the fishbone oscillation, and a collective mode in particle accelerators, are discussed.

  10. Dissociative Electron Attachment to Rovibrationally Excited Molecules

    DTIC Science & Technology

    1987-08-31

    scatt,,;ng by argon have been - present calculations of elastic scattering of electrons and performed by Walker35 and by Fink and Yates %3 using the...A. C. Yates , At. Data 1, 385 (1970). 66p. G. Coleman and J. D. McNutt, Phys. Rev. Lett. 42, 1130 37D. G. Thompson, Proc. R. Soc. London, Ser. A 294...final I bound state, Ps. The reduced masses are gj +O, (rj)= E -H , +i i ’ (16) Pr=mMT/(m +Mr)=am Upon operating on both sides of Eq. (16) by (HI)-E

  11. Near-threshold electron-impact doubly differential cross sections for the ionization of argon and krypton

    SciTech Connect

    Yates, Brent R.; Khakoo, Murtadha A.

    2011-04-15

    We present normalized doubly differential cross sections (DDCS's) for the near-threshold, electron-impact single ionization of argon and krypton, similar to those taken earlier for Ne and Xe [Yates et al., J. Phys. B 42, 095206 (2009)]. The Ar measurements were taken at incident energies of 17, 18, 20, and 30 eV while the Kr measurements were taken at 15, 16, 17.5, and 20 eV. The DDCS scattering angles range from 15 deg. to 120 deg. The differential data are initially normalized to available experimental cross sections for excitation of the ground np{sup 6} to the np{sup 5}(n+1)s excited states of the noble gas and, after integration, to well-established experimental total ionization cross sections of Rapp and Englander-Golden [J. Chem. Phys. 43, 1464 (1965)].

  12. Contribution of near threshold states to dielectronic recombination in recombining plasma with Li-like Al ions

    NASA Astrophysics Data System (ADS)

    Stancalie, V.

    2012-05-01

    The dielectronic recombination of Li-like into Be-like aluminum ions, in laser-produced plasmas with Li-like ions, is re-visited with respect to the contribution of near-threshold states. Results are shown for recombining laser-produced plasma regime. The relativistic Dirac R-matrix calculation is performed to output resonance energy levels and rates. The target energies, and orbitals, are calculated with the extended average level multi-configurational Dirac-Fock method in the general-purpose relativistic atomic structure package (GRASP), while for determining the plasma population densities distribution over the excited Rydberg states, the Atomic Data Analysis System (ADAS) package programs is used.

  13. High-level theoretical rovibrational spectroscopy of HCS+ isotopologues

    NASA Astrophysics Data System (ADS)

    Schröder, B.; Sebald, P.

    2016-12-01

    In this work the rovibrational spectrum of the HCS+ molecular cation is revisited through high-level electronic structure and variational rovibrational calculations. A local potential energy function is built from explicitly correlated coupled-cluster results, incorporating corrections for core-valence, scalar relativistic and higher-order excitation effects. The computed spectroscopic parameters, based on variational calculations with Watson's isomorphic Hamiltonian for linear molecules lead to a nearly perfect agreement with experimentally reported values (Rosenbaum et al., 1989). Furthermore, the documented Fermi resonance within the (0,00, 1) / (0,20, 0) and (1,00, 1) / (1,20, 0) pairs of states is clarified. Based on a newly developed electric dipole moment function transition dipole moments of fundamental transitions are predicted for the most important isotopologues.

  14. Revisiting the (7)Li(p,n)(7)Be reaction near threshold.

    PubMed

    Herrera, María S; Moreno, Gustavo A; Kreiner, Andrés J

    2014-06-01

    In this work we review all the available experimental neutron data for the (7)Li(p,n) reaction near threshold which is necessary to obtain an accurate source model for Monte Carlo simulations in Boron Neutron Capture Therapy. Scattered published experimental results such as cross sections, differential neutron yields and total yields were collected and analyzed, exploring the sensitivity of the fitting parameters to the different possible variables and deriving a consistent working set of parameters to evaluate the neutron source near threshold. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Unimolecular dissociation of CH 3SH + near threshold: A theoretical study

    NASA Astrophysics Data System (ADS)

    Choe, Joong Chul

    2006-04-01

    The unimolecular dissociation of methanethiol cation (CH 3SH +, 1) has been investigated theoretically. Ab initio and Gaussian-2 theory calculations have been performed to obtain the potential energy surface (PES) for loss of H and H 2 from 1. On the basis of the PES obtained, the relative abundances of the two channels near threshold have been calculated by Rice-Ramsperger-Kassel-Marcus modeling. The calculated result agrees with the previous experimental one, suggesting that the dissociation occurs statistically near threshold on the ground electronic state.

  16. Rotational And Rovibrational Energy Transfer In Electron Collisions With Molecules

    NASA Technical Reports Server (NTRS)

    Thuemmel, Helmar T.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Air flows around a hypervelocity reentry vehicle undergo dissociation, rovibrational excitation and ionization. More specifically the air, initially 80% N2 and 20% O2, in the shock layer consists of species such as N, O, N2, O2, NO, N+, O+, N+, O+, NO+ and 2 free electrons. It was pointed out in multi temperature models'' that the temperature of the rotational energy modes and the gas-kinetic translational temperature are quickly equilibrated by a few collisions and rise rapidly to high temperatures as 50000K before falling off to equilibrium value of 10000K. Contrary, the electronic and vibrational temperatures state energy distributions remain low (less than 15000K) because of the slow equilibration. Electron vibrational energy transfer is thought to play a crucial role in such a ionizing flow regime since chemical reaction rates and dissociation depend strongly on the vibrational temperatures. Modeling of these flowfields in principle require the rovibrational excitation and de-excitation cross section data for average electron energies from threshold up to several eV (leV=11605.4 K). In this lecture we focus on theoretical description of rotational effects i.e. energy transfer of electrons to molecules such that the molecular rotational (vojo goes to voj) or vibrational and rotational (v(sub 0)j(sub 0) goes to vj) states are changed. Excitation and de-excitation of electronic states was discussed in a previous talk at this conference.

  17. Rotational And Rovibrational Energy Transfer In Electron Collisions With Molecules

    NASA Technical Reports Server (NTRS)

    Thuemmel, Helmar T.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Air flows around a hypervelocity reentry vehicle undergo dissociation, rovibrational excitation and ionization. More specifically the air, initially 80% N2 and 20% O2, in the shock layer consists of species such as N, O, N2, O2, NO, N+, O+, N+, O+, NO+ and 2 free electrons. It was pointed out in multi temperature models'' that the temperature of the rotational energy modes and the gas-kinetic translational temperature are quickly equilibrated by a few collisions and rise rapidly to high temperatures as 50000K before falling off to equilibrium value of 10000K. Contrary, the electronic and vibrational temperatures state energy distributions remain low (less than 15000K) because of the slow equilibration. Electron vibrational energy transfer is thought to play a crucial role in such a ionizing flow regime since chemical reaction rates and dissociation depend strongly on the vibrational temperatures. Modeling of these flowfields in principle require the rovibrational excitation and de-excitation cross section data for average electron energies from threshold up to several eV (leV=11605.4 K). In this lecture we focus on theoretical description of rotational effects i.e. energy transfer of electrons to molecules such that the molecular rotational (vojo goes to voj) or vibrational and rotational (v(sub 0)j(sub 0) goes to vj) states are changed. Excitation and de-excitation of electronic states was discussed in a previous talk at this conference.

  18. Exclusive near threshold two-pion production with the MOMO experiment at COSY

    NASA Astrophysics Data System (ADS)

    Bavink, S.; Bellemann, F.; Berg, A.; Bisplinghoff, J.; Bohlscheid, G.; Ernst, J.; Henrich, C.; Hinterberger, F.; Ibald, R.; Jahn, R.; Jarczyk, L.; Joosten, R.; Kozela, A.; Machner, H.; Magiera, A.; Maschuw, R.; Mayer-Kuckuk, T.; Mertler, G.; Munkel, J.; Neumann-Cosel, P. v.; Rosendaal, D.; Rossen, P. v.; Schnitker, H.; Scho, K.; Smyrski, J.; Strzalkowski, A.; Tölle, R.; Wurzinger, R.

    1998-03-01

    Near threshold two pion production via the reaction pd → 3Heπ +π - was measured kinematically complete with the MOMO experiment at COSY. A remarkable deviation of the obtained two pion invariant mass spectra from phase space as well as a predominant back to back and sidewise emission of the two pions was observed.

  19. Exclusive near threshold two-pion production with the MOMO experiment at COSY

    NASA Astrophysics Data System (ADS)

    Bavink, S.; Bellemann, F.; Berg, A.; Bisplinghoff, J.; Bohlscheid, G.; Ernst, J.; Henrich, C.; Hinterberger, F.; Ibald, R.; Jahn, R.; Jarczyk, L.; Joosten, R.; Kozela, A.; Machner, H.; Magiera, A.; Maschuw, R.; Mayer-Kuckuk, T.; Mertler, G.; Munkel, J.; Neumann-Cosel, P. v.; Rosendaal, D.; Rossen, P. v.; Schnitker, H.; Scho, K.; Smyrski, J.; Strzalkowski, A.; Tölle, R.; Wurzinger, R.

    1997-05-01

    Near threshold two pion production via the reaction pd→3Heπ+π- was measured kinematically complete with the MOMO experiment at COSY. A remarkable deviation of the obtained two pion invariant mass spectra from phase space as well as a predominant sidewise and back to back emission of the two mesons was observed.

  20. A quantum defect theory of near-threshold molecular Feshbach resonance states

    NASA Astrophysics Data System (ADS)

    Julienne, Paul; Chin, Cheng; Tiesinga, Eite

    2008-05-01

    The framework provided by multichannel quantum defect theory (MQDT) [1,2] provides an excellent way to classify the near-threshold molecular vibrational states associated with magnetically tunable Feshbach resonances of two cold atoms. The separation of energy and length scales between long- and short-range interactions permit the definition of a dimensionless resonance strength parameter that determines, along with the analytic properties of the long-range potential, near threshold scattering and bound state properties. The MQDT bound state equations based on the long-range potential [2] yield a simple theory for near-threshold bound states. While resonance strengths span order of magnitude in practice, near-threshold molecular bound states fall into two broad classes, those where the bound state has primarily entrance channel character or those where it has primarily closed channel character as magnetic field is tuned over the width of the resonance. Most resonances tend to be closed channel dominated, including the very broad ^7Li resonance near 720 G, whereas the ^85Rb, ^6Li, and ^40K resonances successfully used in many quantum degenerate gas experiments are open channel dominated. See also [3]. 1. F. H. Mies, J. Chem. Phys. 80, 2514(1984) 2. F. H. Mies and M. Raoult, Phys. Rev. A 62, 012708(2000) 3. T. K"ohler, K. G'oral, and P. S. Julienne, Rev. Mod. Phys.78, 1311 (2006)

  1. Near-threshold production of heavy quarks with QQbar_threshold

    NASA Astrophysics Data System (ADS)

    Beneke, M.; Kiyo, Y.; Maier, A.; Piclum, J.

    2016-12-01

    We describe the QQbar_threshold library for computing the production cross section of heavy quark-antiquark pairs near threshold at electron-positron colliders. The prediction includes all presently known QCD, electroweak, Higgs, and nonresonant corrections in the combined nonrelativistic and weak-coupling expansion.

  2. Near threshold enhancement of the p p-bar mass spectrum in J/Psi decay

    SciTech Connect

    A. Sibirtsev; J. Haidenbauer; S. Krewald; Ulf-G. Meissner; A.W. Thomas

    2004-12-01

    We investigate the nature of the near-threshold enhancement in the p {bar p} invariant mass spectrum of the reaction J/{Psi} {yields} {gamma} p {bar p} reported recently by the BES Collaboration. Using the Juelich N {bar N} model we show that the mass dependence of the p {bar p} spectrum close to the threshold can be reproduced by the S-wave p {bar p} final state interaction in the isospin I=1 state within the Watson-Migdal approach. However, because of our poor knowledge of the N {bar N} interaction near threshold and of the J/{Psi} {yields} {gamma} p {bar p} reaction mechanism and in view of the controversial situation in the decay J/{Psi} {yields} {pi}{sup 0} p {bar p}, where no obvious signs of a p {bar p} final state interaction are seen, explanations other than final state interactions cannot be ruled out at the present stage.

  3. Near-threshold quantization for potentials with inverse-cube tails

    SciTech Connect

    Mueller, Tim-Oliver; Friedrich, Harald

    2011-02-15

    For potential wells with long-range attractive tails proportional to -1/r{sup 3}, as occur in the resonant dipole-dipole interaction in homonuclear alkali-metal dimers, we present a highly accurate analytical expression for the tail contribution to the quantization function F(E). This quantization function determines the near-threshold bound-state energies via the quantization rule n{sub th}-n=F(E{sub n}). The performance of the quantization function derived in this paper is demonstrated by applying it to a model Lennard-Jones potential and to vibrational bound-state spectra of sodium dimers (Na{sub 2}). These results are compared with those obtained via the semiclassical LeRoy-Bernstein formula which neglects quantum effects that are important in the near-threshold regime.

  4. Near-threshold neutral pion electroproduction at high momentum transfers and generalized form factors

    NASA Astrophysics Data System (ADS)

    Khetarpal, P.; Stoler, P.; Aznauryan, I. G.; Kubarovsky, V.; Adhikari, K. P.; Adikaram, D.; Aghasyan, M.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Anghinolfi, M.; Avakian, H.; Baghdasaryan, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Charles, G.; Cole, P. L.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Doughty, D.; Dugger, M.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Fersch, R.; Fleming, J. A.; Fradi, A.; Gabrielyan, M. Y.; Garçon, M.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guegan, B.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hicks, K.; Ho, D.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, F. J.; Koirala, S.; Kubarovsky, A.; Kuleshov, S. V.; Kvaltine, N. D.; Lewis, S.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Mao, Y.; Martinez, D.; Mayer, M.; McKinnon, B.; Meyer, C. A.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Moutarde, H.; Munevar, E.; Munoz Camacho, C.; Nadel-Turonski, P.; Nasseripour, R.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Park, S.; Pasyuk, E.; Phelps, E.; Phillips, J. J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Puckett, A. J. R.; Raue, B. A.; Ricco, G.; Rimal, D.; Ripani, M.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M. S.; Salgado, C.; Saylor, N. A.; Schott, D.; Schumacher, R. A.; Seder, E.; Seraydaryan, H.; Sharabian, Y. G.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S. S.; Stepanyan, S.; Strakovsky, I. I.; Strauch, S.; Taiuti, M.; Tang, W.; Taylor, C. E.; Tkachenko, S.; Ungaro, M.; Vernarsky, B.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Weinstein, L. B.; Weygand, D. P.; Wood, M. H.; Zachariou, N.; Zhang, J.; Zhao, Z. W.; Zonta, I.

    2013-04-01

    We report the measurement of near-threshold neutral pion electroproduction cross sections and the extraction of the associated structure functions on the proton in the kinematic range Q2 from 2 to 4.5 GeV2 and W from 1.08 to 1.16 GeV. These measurements allow us to access the dominant pion-nucleon s-wave multipoles E0+ and S0+ in the near-threshold region. In the light-cone sum-rule framework (LCSR), these multipoles are related to the generalized form factors G1π0p(Q2) and G2π0p(Q2). The data are compared to these generalized form factors and the results for G1π0p(Q2) are found to be in good agreement with the LCSR predictions, but the level of agreement with G2π0p(Q2) is poor.

  5. Model-Independent Determination of the Compositeness of Near-Threshold Quasibound States

    NASA Astrophysics Data System (ADS)

    Kamiya, Yuki; Hyodo, Tetsuo

    We study the compositeness of near-threshold states to clarify the internal structure of exotic hadron candidates. Within the framework of effective field theory, we extend the Weinberg's weak-binding relation to include the nearby CDD (Castillejo-Dalitz-Dyson) pole contribution with the help of the Padé approximant. Finally, using the extended relation, we conclude that the CDD pole contribution to the Λ(1405) baryon in the bar{K}N amplitude is negligible.

  6. On Microstructural Control of Near-Threshold Fatigue Crack Growth in 7000-Series Aluminum Alloys.

    DTIC Science & Technology

    1982-04-02

    crack growth rate behavior for different microstruc - tural conditions in aluminum alloys is also in quantitative agreement with the predictions of the...34 .. . -~ Introduction ! A number of recent studies have been conducted to ascertain the influence of microstructure on fatigue crack growth behavior in aluminum...161. The da/dN data, obtained over a very broad spectrum of ,K, characterize the near-threshold growth-rate behavior unusually well. Predictions of

  7. Analyses of Fatigue Crack Growth and Closure Near Threshold Conditions for Large-Crack Behavior

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.

    1999-01-01

    A plasticity-induced crack-closure model was used to study fatigue crack growth and closure in thin 2024-T3 aluminum alloy under constant-R and constant-K(sub max) threshold testing procedures. Two methods of calculating crack-opening stresses were compared. One method was based on a contact-K analyses and the other on crack-opening-displacement (COD) analyses. These methods gave nearly identical results under constant-amplitude loading, but under threshold simulations the contact-K analyses gave lower opening stresses than the contact COD method. Crack-growth predictions tend to support the use of contact-K analyses. Crack-growth simulations showed that remote closure can cause a rapid rise in opening stresses in the near threshold regime for low-constraint and high applied stress levels. Under low applied stress levels and high constraint, a rise in opening stresses was not observed near threshold conditions. But crack-tip-opening displacement (CTOD) were of the order of measured oxide thicknesses in the 2024 alloy under constant-R simulations. In contrast, under constant-K(sub max) testing the CTOD near threshold conditions were an order-of-magnitude larger than measured oxide thicknesses. Residual-plastic deformations under both constant-R and constant-K(sub max) threshold simulations were several times larger than the expected oxide thicknesses. Thus, residual-plastic deformations, in addition to oxide and roughness, play an integral part in threshold development.

  8. Analytical and Experimental Study of Near-Threshold Interactions Between Crack Closure Mechanisms

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Riddell, William T.; Piascik, Robert S.

    2003-01-01

    The results of an analytical closure model that considers contributions and interactions between plasticity-, roughness-, and oxide-induced crack closure mechanisms are presented and compared with experimental data. The analytical model is shown to provide a good description of the combined influences of crack roughness, oxide debris, and plasticity in the near-threshold regime. Furthermore, analytical results indicate that closure mechanisms interact in a non-linear manner such that the total amount of closure is not the sum of closure contributions for each mechanism.

  9. Reaction π+p-->π+π0p near threshold and chiral symmetry breaking

    NASA Astrophysics Data System (ADS)

    Počanić, D.; Frlež, E.; Assamagan, K. A.; Chen, J. P.; Keeter, K. J.; Marshall, R. M.; Minehart, R. C.; Smith, L. C.; Dodge, G. E.; Hanna, S. S.; King, B. H.; Knudson, J. N.

    1994-02-01

    We have measured total cross sections for the reaction π+p-->π+π-p at incident pion kinetic energies of 190, 200, 220, 240, and 260 MeV. We use this result to deduce a new value of the chiral symmetry breaking parameter, ξ=-0.25+/-0.10, in a global constrained fit of the five ππN near-threshold amplitudes. Consequently, we report new soft pion model values for the s-wave ππ scattering lengths.

  10. Near-Threshold Fatigue Crack Growth Behavior of Fine-Grain Nickel-Based Alloys

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Piascik, Robert S.

    2003-01-01

    Constant-Kmax fatigue crack growth tests were performed on two finegrain nickel-base alloys Inconel 718 (DA) and Ren 95 to determine if these alloys exhibit near-threshold time-dependent crack growth behavior observed for fine-grain aluminum alloys in room-temperature laboratory air. Test results showed that increases in K(sub max) values resulted in increased crack growth rates, but no evidence of time-dependent crack growth was observed for either nickel-base alloy at room temperature.

  11. Chiral power counting and pp {r_arrow} pp{pi}{sup 0} near threshold

    SciTech Connect

    Van Kolck, U.; Miller, G.A.

    1995-10-01

    The pp {r_arrow} pp{pi}{sup 0} reaction is studied near threshold using power counting arguments based on chiral perturbation theory with an explicit {Delta} degree of freedom. Important contributions include the so-called impulse term, rescattering via the {Delta} and rescattering via the (off-shell) seagull term responsible for s-wave pion-nucleon scattering. These contributions largely cancel so that their sum greatly underpredicts the total cross-section. Other mechanisms are also discussed. The inclusion of the previously proposed {sigma} meson exchange mechanism is not sufficient to resolve the discrepancy with experiment.

  12. Near-Threshold Measurement of γn --> pπ- at MAX-lab

    NASA Astrophysics Data System (ADS)

    O'Rielly, Grant

    2014-03-01

    One of the outstanding questions in nuclear science is to be able to describe the dynamical properties of the nucleon using the framework provided by QCD. Pion photoproduction near threshold is one process where both experimental measurements and theoretical calculations can produce valid and useful results. Consequently, high-quality measurements of this fundamental nuclear process can be used to test the predictions of various theoretical approaches. These measurements also provide data to improve the SAID and MAID partial-wave analyses used in the interpretation of other measurements. The Photon Tagging Facility at MAX-lab in Lund, Sweden is uniquely suited to perform measurements of pion photoproduction at energies between threshold and the Δ-resonance. The PIONS@MAXLAB Collaboration is performing a measurement of the γn --> pπ- channel very close to threshold. Using a LD2 target and the reaction γd --> ppπ- , the π- is captured on another deuteron creating a high-energy photon which was detected using three large NaI spectrometers. These new near-threshold data will be used to better evaluate the threshold E0+(π- p) amplitude, which can be compared with the theoretical predictions. Initial results will be presented. This work supported by NSF OISE/IRES award 0553467.

  13. Near-threshold absolute photoionization cross-sections of some reaction intermediates in combustion

    NASA Astrophysics Data System (ADS)

    Wang, Juan; Yang, Bin; Cool, Terrill A.; Hansen, Nils; Kasper, Tina

    2008-02-01

    The use of photoionization mass spectrometry for the development of quantitative kinetic models for the complex combustion chemistry of both conventional hydrocarbon fuels and oxygenated biofuels requires near-threshold measurements of absolute photoionization cross-sections for numerous reaction intermediates. Near-threshold absolute cross-sections for molecular and dissociative photoionization for 20 stable reaction intermediates (methane, ethane, propane, n-butane, cyclopropane, methylcyclopentane, 1-butene, cis-2-butene, isobutene, 1-pentene, cyclohexene, 3,3-dimethyl-1-butene, 1,3-hexadiene, 1,3-cyclohexadiene, methyl acetate, ethyl acetate, tetrahydrofuran, propanal, 1-butyne, 2-butyne) are presented. Previously measured total photoionization cross-sections for 9 of these molecules are in good agreement with the present results. The measurements are performed with photoionization mass spectrometry (PIMS) using a monochromated VUV synchrotron light source with an energy resolution of 40 meV (fwhm) comparable to that used for flame-sampling molecular beam PIMS studies of flame chemistry and reaction kinetics.

  14. Near-threshold ω and φ meson productions in pp collisions

    NASA Astrophysics Data System (ADS)

    Tsushima, K.; Nakayama, K.

    2003-09-01

    Using a relativistic effective Lagrangian at the hadronic level, near-threshold ω- and φ-meson productions in proton-proton (pp) collisions, pp→ppω/φ, are studied within the distorted wave Born approximation. Both initial and final state pp interactions are included. In addition to total cross section data, both ω and φ angular distribution data are used to constrain further the model parameters. For the pp→ppω reaction, we consider two different possibilities: with and without the inclusion of nucleon resonances. The nucleon resonances are included in a way to be consistent with the π-p→ωn reaction. It is shown that the inclusion of nucleon resonances can describe the data better overall than without their inclusion. However, the SATURNE data in the range of excess energies Q<31 MeV are still underestimated by about a factor of 2. As for the pp→ppφ reaction, it is found that the presently limited available data from DISTO can be reproduced by four sets of values for the vector and tensor φNN coupling constants. Further measurements of the energy dependence of the total cross section near threshold energies should help to constrain better the φNN coupling constant.

  15. Influence of rovibrational excitation on the non-diabatic state-to-state dynamics for the Li(2p) + H2 → LiH + H reaction.

    PubMed

    He, Di; Yuan, Jiuchuang; Chen, Maodu

    2017-06-08

    The non-adiabatic state-to-state dynamics of the Li(2p) + H2 → LiH + H reaction has been studied using the time-dependent wave packet method, based on a set of diabatic potential energy surfaces recently developed by our group. Integral cross sections (ICSs) can be increase more than an order of magnitude by the vibrational excitation of H2, whereas the ICSs are barely affected by the rotational excitation of H2. Moreover, ICSs of the title reaction with vibrationally excited H2 decrease rapidly with increasing collision energy, which is a typical feature of non-threshold reaction. This phenomenon implies that the title reaction can transformed from an endothermic to an exothermic reaction by vibrational excitation of H2. With the increase of the collision energy, the sideways and backward scattered tendencies of LiH for the Li(2p) + H2(v = 0, j = 0, 1) → LiH + H reactions are enhanced slightly, while the backward scattering tendency of LiH for the Li(2p) + H2(v = 1, j = 0) → LiH + H reaction becomes remarkably weakened. For the reaction with vibrationally excited H2 molecule, both direct and indirect reaction mechanism exist simultaneously.

  16. Variability of Rotational Temperatures from Different OH Rovibrational Levels

    NASA Astrophysics Data System (ADS)

    Vimal, D. V.; Slanger, T. G.

    2011-12-01

    TThe Meinel band emission lines from rovibrationally excited OH in its electronic ground state in the nightglow are widely used as a diagnostic tool to investigate key mesospheric variables such as temperature, tides, and gravity waves. The OH rotational temperature has been extensively studied to ascertain both long- and short-term variability in the upper atmosphere. Current controversy in the literature regarding the possible variability of temperatures deduced from different OH rovibrational levels limits our ability to compare data from different sources. Researchers tend to use a monitoring vibrational level for OH Meinel bands that is most convenient for their instrument. Background sky spectra captured by astronomical instruments provide detailed records of optical emissions in the upper atmosphere. For this study we utilized existing sky spectra from the Keck telescopes in Mauna Kea and the Very Large Telescope in Chile for the OH Meinel bands bound by the extremes (υ = 3, 8). We compared these results with the temperatures deduced from the O2 0-1 Atmospheric band at 865 nm. This latter emission, emanating from a long-lived species, should represent the true kinetic temperature at the altitude of emission and therefore puts a cap on how high the temperature difference can be between the nominal OH altitude (87 km) and the 95-km altitude of the O2 emission. We present the results of our analysis and discuss the implications for mesospheric temperature retrievals from OH emissions. This work was supported by NSF grant ATM-0924781 from NSF CEDAR.

  17. ROVIBRATIONAL QUENCHING RATE COEFFICIENTS OF HD IN COLLISIONS WITH He

    SciTech Connect

    Nolte, J. L.; Stancil, P. C.; Lee, T.-G.; Balakrishnan, N.; Forrey, R. C. E-mail: stancil@physast.uga.edu E-mail: naduvala@unlv.nevada.edu

    2012-01-01

    Along with H{sub 2}, HD has been found to play an important role in the cooling of the primordial gas for the formation of the first stars and galaxies. It has also been observed in a variety of cool molecular astrophysical environments. The rate of cooling by HD molecules requires knowledge of collisional rate coefficients with the primary impactors, H, He, and H{sub 2}. To improve knowledge of the collisional properties of HD, we present rate coefficients for the He-HD collision system over a range of collision energies from 10{sup -5} to 5 Multiplication-Sign 10{sup 3} cm{sup -1}. Fully quantum mechanical scattering calculations were performed for initial HD rovibrational states of j = 0 and 1 for v = 0-17 which utilized accurate diatom rovibrational wave functions. Rate coefficients of all {Delta}v = 0, -1, and -2 transitions are reported. Significant discrepancies with previous calculations, which adopted a small basis and harmonic HD wave functions for excited vibrational levels, were found for the highest previously considered vibrational state of v = 3. Applications of the He-HD rate coefficients in various astrophysical environments are briefly discussed.

  18. Hydrodynamics of the molten metal in a vacuum arc cathode spot at near-threshold currents

    NASA Astrophysics Data System (ADS)

    Mesyats, G. A.; Zubarev, N. M.

    2013-05-01

    The extrusion of the molten metal from a microcrater formed on a metal cathode during the operation of a vacuum arc is considered. The problem is thought to be similar to the classical hydrodynamic problem of a liquid drop impact on a solid surface. Based on this analogy, the conditions are analyzed under which the liquid will change its regular behavior (spreading over the cathode surface) into a singular behavior (formation of microjets and droplets). It is shown that the conditions realized in vacuum arc cathode spots at near-threshold currents are close to the threshold conditions for splashing of the molten metal. This points to a considerable contribution of hydrodynamic processes to the self-sustained operation of a vacuum arc and, in particular, gives grounds to relate the existence of a threshold arc current to the existence of a splashing threshold for liquid metal.

  19. Study of Near-Threshold Fatigue Crack Propagation in Pipeline Steels in High Pressure Environments

    NASA Technical Reports Server (NTRS)

    Mitchell, M.

    1981-01-01

    Near threshold fatigue crack propagation in pipeline steels in high pressure environments was studied. The objective was to determine the level of threshold stress intensity for fatigue crack growth rate behavior in a high strength low alloy X60 pipeline-type steel. Complete results have been generated for gaseous hydrogen at ambient pressure, laboratory air at ambient pressure and approximately 60% relative humidity as well as vacuum of 0.000067 Pa ( 0.0000005 torr) at R-ratios = K(min)/K(max) of 0.1, 0.5, and 0.8. Fatigue crack growth rate behavior in gaseous hydrogen, methane, and methane plus 10 percent hydrogen at 6.89 MPa (100 psi) was determined.

  20. Report on the workshop on new directions in soft x-ray near-threshold phenomena

    SciTech Connect

    Lindle, D.W.; Perera, R.C.C.

    1988-07-01

    The ''Workshop on New Directions in Soft X-Ray Near-Threshold Phenomena'' was held at the Asilomar Conference Center in Pacific Grove, CA on March 1--4, 1987. It was attended by 59 scientists from 8 countries, representing 27 institutions. Major funding for the meeting was donated by L-Division of the Lawrence Livermore National Laboratory, who hosted and organized two previous workshops on photoabsorption and scattering in the soft x-ray energy range. Additional funding was provided by the User's Group of the Advanced Light Source. The Workshop, as its name suggests, emphasized physical phenomena in atoms, molecules, and solids near inner-shell thresholds. Of particular interest were threshold ionization, post-collisional interaction, resonant photoemission and fluorescence, and multi-electron effects such as shake-up and shake-off. In these areas and others, special consideration was given to presenting recent discoveries and potential ''new directions'' for future work.

  1. Phenomenology of near-threshold states: a practical parametrisation for the line shapes

    NASA Astrophysics Data System (ADS)

    Guo, F.-K.; Hanhart, C.; Kalashnikova, Yu. S.; Matuschek, P.; Mizuk, R. V.; Nefediev, A. V.; Wang, Q.; Wynen, J.-L.

    2017-03-01

    In the last decade many states in the spectrum of charmonium and bottomonium have been observed experimentally above the lowest open-flavour threshold. Most of these states reside in the vicinity of strong thresholds and show properties that cannot be captured by simple quark models. Description and understanding of such exotic states is a challenge for the phenomenology of strong interactions, since it requires building adequate theoretical tools and approaches. In this work, a practical parametrisation for the line shapes of near threshold resonance(s) is derived in the framework of a coupled-channel model which includes an arbitrary number of elastic and inelastic channels as well as of bare pole terms. Parameters of the distribution have a direct relation to phenomenology and the resulting analytical parametrisation is therefore ideally suited to harvest the full information content provided by the measurements and to establish a link between the experimental data and their theoretical interpretation.

  2. Spin-tagged electron-hydrogen scattering: Ionization in the near-threshold region

    SciTech Connect

    Guo, X.Q.; Crowe, D.M.; Lubell, M.S.; Tang, F.C.; Vasilakis, A.; Slevin, J.; Eminyan, M. Department of Experimental Physics, St. Patrick's College, Maynooth, Maynooth, County Kildare Laboratoire de Physique Atomique, Tour 24, Universite Paris VII, F-75251 Paris )

    1990-10-08

    We use beams of polarized electrons and polarized hydrogen atoms to measure the ionization-rate asymmetry, {Delta}{sub {ital I}}=({ital R}({up arrow}{down arrow}){minus}{ital R}({up arrow}{up arrow}))/({ital R}({up arrow}{down arrow})+{ital R}({up arrow}{up arrow})), in the near-threshold region, where {ital R}({up arrow}{down arrow}) and {ital R}({up arrow}{up arrow}) are the ionization rates when the electron spin is antiparallel and parallel, respectively, to the atomic spins. Within 1.7 eV above threshold, our results reveal the presence of structure, which heretofore has not been predicted by any conventional theoretical calculation.

  3. Measurement of the Proton + Proton Going to Proton + Proton + Neutral Pion Cross-Section Near Threshold

    NASA Astrophysics Data System (ADS)

    Ross, M. Alan

    1991-02-01

    The first nuclear physics experiment at the IUCF Cooler is a measurement of the p+ptop+p+ pi^0 cross section near threshold. The Cooler, together with a thin internal H_2 gas jet target, allows for a precise cross section measurement by providing well-defined interaction energies and by eliminating background from p-nucleus pion production which has a much lower threshold. A cylindrically symmetric detector system has been installed in one of the straight sections of the ring and is used to detect the coincident protons in the exit channel with good energy and angular resolution. The mass of the unobserved is then deduced. Elastically scattered protons were detected at the same time and by the same detector as pion production events. Elastic scattering was used for normalization to obtain an absolute p+p top+p+pi^0 cross section.

  4. Photon scattering on /sup 238/U and the interpretation of near-threshold photofission resonances

    SciTech Connect

    Birenbaum, Y.; Alarcon, R.; Hoblit, S.D.; Laszewski, R.M.; Nathan, A.M.

    1987-10-01

    Cross sections for photon elastic scattering have been measured for /sup 238/U between 4.8 and 6.4 MeV with an energy resolution of about 50 keV. These data have been used along with existing photofission data to infer the total photoabsorption cross section sigma/sub T/ and the fission transmission coefficient T/sub f/ below neutron threshold. We find that the inferred sigma/sub T/ varies smoothly with energy and generally follows the extrapolated tail of the giant dipole resonance, and that T/sub f/ shows a broad bump between 5.6 and 5.9 MeV. These results strongly support the contention that resonances seen in near-threshold photofission cross sections are due to the fission and not the photon channel .

  5. Identifying the structure of near-threshold states from the line shape

    NASA Astrophysics Data System (ADS)

    Chen, Guo-Ying; Huo, Wen-Sheng; Zhao, Qiang

    2015-09-01

    We revisit the compositeness theorem proposed by Weinberg in an effective field theory (EFT) and explore criteria which are sensitive to the structure of S-wave threshold states. On a general basis, we show that the wave function renormalization constant Z, which is the probability of finding an elementary component in the wave function of a threshold state, can be explicitly introduced in the description of the threshold state. As an application of this EFT method, we describe the near-threshold line shape of the D*0D̅0 invariant mass spectrum in B→D*0D̅0K and determine a nonvanishing value of Z. It suggests that the X(3872) as a candidate of the D*0D̅0 molecule may still contain a small cc¯ core. This elementary component, on the one hand, explains its production in the B meson decay via a short-distance mechanism, and on the other hand, is correlated with the D*0D̅0 threshold enhancement observed in the D*0D̅0 invariant mass distributions. Meanwhile, we also show that if Z is non-zero, the near-threshold enhancement of the D*0D̅0 mass spectrum in the B decay will be driven by the short-distance production mechanism. Supported by National Natural Science Foundation of China (11147022, 11035006, 11305137), Chinese Academy of Sciences (KJCX2-EW-N01), Ministry of Science and Technology of China (2009CB825200), DFG and NSFC (11261130311) through funds provided to the Sino-German CRC 110 “Symmetries and the Emergence of Structure in QCD”, and Doctor Foundation of Xinjiang University (BS110104)

  6. Full-dimensional quantum dynamics of rovibrationally inelastic scattering between CN and H2.

    PubMed

    Yang, Benhui; Wang, X H; Stancil, P C; Bowman, J M; Balakrishnan, N; Forrey, R C

    2016-12-14

    We report six-dimensional (6D) potential energy surface (PES) and rovibrational scattering calculations for the CN-H2 collision system. The PES was computed using the high-level ab initio spin-restricted coupled-cluster with single, double, and perturbative triple excitations-F12B method and fitted to an analytic function using an invariant polynomial method in 6D. Quantum close-coupling calculations are reported for rotational transitions in CN by H2 and D2 collisions in 6D as well as four-dimensional (4D) within a rigid rotor model for collision energies of 1.0-1500 cm(-1). Comparisons with experimental data and previous 4D calculations are presented for CN rotational levels j1 = 4 and 11. For the first time, rovibrational quenching cross sections and rate coefficients of CN (v1 = 1,j1 = 0) in collisions with para- and ortho-H2 are also reported in full-dimension. Agreement for pure rotational transitions is found to be good, but no experimental data on rovibrational collisional quenching for CN-H2 are available. Applications of the current rotational and rovibrational rate coefficients in astrophysical modeling are briefly discussed.

  7. Full-dimensional quantum dynamics of rovibrationally inelastic scattering between CN and H2

    NASA Astrophysics Data System (ADS)

    Yang, Benhui; Wang, X. H.; Stancil, P. C.; Bowman, J. M.; Balakrishnan, N.; Forrey, R. C.

    2016-12-01

    We report six-dimensional (6D) potential energy surface (PES) and rovibrational scattering calculations for the CN-H2 collision system. The PES was computed using the high-level ab initio spin-restricted coupled-cluster with single, double, and perturbative triple excitations-F12B method and fitted to an analytic function using an invariant polynomial method in 6D. Quantum close-coupling calculations are reported for rotational transitions in CN by H2 and D2 collisions in 6D as well as four-dimensional (4D) within a rigid rotor model for collision energies of 1.0-1500 cm-1. Comparisons with experimental data and previous 4D calculations are presented for CN rotational levels j1 = 4 and 11. For the first time, rovibrational quenching cross sections and rate coefficients of CN (v1 = 1,j1 = 0) in collisions with para- and ortho-H2 are also reported in full-dimension. Agreement for pure rotational transitions is found to be good, but no experimental data on rovibrational collisional quenching for CN-H2 are available. Applications of the current rotational and rovibrational rate coefficients in astrophysical modeling are briefly discussed.

  8. Generating Molecular Rovibrational Coherence by Two-Photon Femtosecond Photoassociation of Thermally Hot Atoms

    SciTech Connect

    Rybak, Leonid; Levin, Liat; Amitay, Zohar; Amaran, Saieswari; Kosloff, Ronnie; Tomza, Michal; Moszynski, Robert; Koch, Christiane P.

    2011-12-30

    The formation of diatomic molecules with rotational and vibrational coherence is demonstrated experimentally in free-to-bound two-photon femtosecond photoassociation of hot atoms. In a thermal gas at a temperature of 1000 K, pairs of magnesium atoms, colliding in their electronic ground state, are excited into coherent superpositions of bound rovibrational levels in an electronically excited state. The rovibrational coherence is probed by a time-delayed third photon, resulting in quantum beats in the UV fluorescence. A comprehensive theoretical model based on ab initio calculations rationalizes the generation of coherence by Franck-Condon filtering of collision energies and partial waves, quantifying it in terms of an increase in quantum purity of the thermal ensemble. Our results open the way to coherent control of a binary reaction.

  9. Cortical processing of near-threshold tactile stimuli in a paired-stimulus paradigm--an MEG study.

    PubMed

    Wühle, Anja; Preissl, Hubert; Braun, Christoph

    2011-08-01

    In the present magnetoencephalography study, we applied a paired-stimulus paradigm to study the weak cortical responses evoked by near-threshold tactile prime stimuli by means of their attenuating effect on the cortical responses evoked by subsequently applied above-threshold test stimuli. In stimulus pairs with adequate interstimulus intervals (ISIs), the extent of test stimulus response attenuation is related to the amplitude of prime stimulus responses, and the duration of the attenuating effect indicates how long memory traces of a prime stimulus reside in cortical areas. We hypothesized that the attenuation of test stimulus responses, studied for ISIs of 30, 60 and 150 ms, would provide insight into the temporal dynamics of near-threshold stimulus processing in primary (SI) and secondary somatosensory cortex (SII), and reveal differences in response amplitude due to conscious perception. Attenuation of test stimulus responses in SI was observed for ISIs up to 60 ms, whereas in SII the effect outlasted the ISI of 150 ms. Differences due to conscious perception of the near-threshold stimuli were only observed in SII with stronger attenuation for perceived than for missed near-threshold stimuli. Applying this indirect approach to near-threshold stimulus processing, we could show that the extent and duration of response attenuation is related to prime stimulus processing and differential temporal and functional characteristics of near-threshold stimulus information processing in SI and SII: transient processing of basic stimulus information not sufficient for conscious perception in SI and long-lasting activations involving conscious perception in SII. © 2011 The Authors. European Journal of Neuroscience © 2011 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

  10. Reaction πN → ππN near threshold

    SciTech Connect

    Frlez, Emil

    1993-11-01

    The LAMPF E1179 experiment used the π0 spectrometer and an array of charged particle range counters to detect and record π+π0, π0p, and π+π0p coincidences following the reaction π+p → π0π+p near threshold. The total cross sections for single pion production were measured at the incident pion kinetic energies 190, 200, 220, 240, and 260 MeV. Absolute normalizations were fixed by measuring π+p elastic scattering at 260 MeV. A detailed analysis of the π0 detection efficiency was performed using cosmic ray calibrations and pion single charge exchange measurements with a 30 MeV π- beam. All published data on πN → ππN, including our results, are simultaneously fitted to yield a common chiral symmetry breaking parameter ξ =-0.25±0.10. The threshold matrix element |α00π+p)| determined by linear extrapolation yields the value of the s-wave isospin-2 ππ scattering length α$2\\atop{0}$(ππ) = -0.041±0.003 m$-1\\atop{π}$-1, within the framework of soft-pion theory.

  11. Influence of the Atomic Potential on Near-Threshold RABBITT Measurements

    NASA Astrophysics Data System (ADS)

    Kiesewetter, Dietrich; Schoun, Stephen; Camper, Antoine; Agostini, Pierre; Dimauro, Louis; Jones, Robert

    2015-05-01

    We have used the RABBITT technique [P. M. Paul et al., Science 292, 1689 (2001)] to study IR-induced continuum transitions involving near-threshold, XUV photoelectrons from He, Ne, and Ar atoms. Energy exchange between ionized electrons and intense oscillating fields plays an essential role in many strong field physics phenomena. For large fields and/or electron energies, the parent ion plays a negligible role in the energy transfer process. This fact is exploited by RABBITT and attosecond streaking techniques for characterizing attosecond pulse trains and isolated pulses, respectively. However, for low energy electrons in weak to moderate dressing fields, the atomic potential influences the energy transfer process, modifying the relative phase and amplitude of photoelectron sidebands in a RABBITT measurement (or the final momentum and apparent photoionization delay in a streaking experiment). For the RABBITT experiments, intense 1.3 micron pulses are used to generate the XUV harmonics for photoionization, and provide the phase-locked dressing field. In principle, the energy-dependence of the measured side-band amplitudes and phases might be used to extract information about the atomic binding potential. Supported by the U.S. DOE, Office of Science, BES, Award # DE-FG02-04ER15614 (LFD) and DE-FG02-00ER15053 (RRJ).

  12. Experimental investigation of the electron impact ionization cross-section behaviour near threshold

    SciTech Connect

    Winkler, C.; Maerk, T.D.

    1995-12-31

    The shape of the electron impact ionization cross-section near the threshold and the appearance energies AE of atomic or molecular ions are of fundamental interest in atomic physics as well as in many applications, e.g. in plasma physics. A large number of experiments and several theoretical approaches have already been presented, which predict either a linear dependences or a cross-section given by {rho} {proportional_to} (E{sub e}-AE){sup 1.13}, as reported for the first time by Wannier. Indeed, until today it is not yet clear what dependence actually has to be assumed; especially in the experiments two serious problems arise, namely the determination of the absolute energy scale and the influence of the energy spread on the measured curve. In this work a further attempt is made to deduce the shape of the ionisation cross-section near threshold and the appearance energy from experimental data obtained by using a novel molecular beam apparatus in combination with a time-of-flight technique.

  13. Photoproduction of hidden-charm states in the reaction near threshold

    NASA Astrophysics Data System (ADS)

    Huang, Yin; Xie, Ju-Jun; He, Jun; Chen, Xurong; Zhang, Hong-Fei

    2016-12-01

    We report on a theoretical study of the hidden charm states in the reaction near threshold within an effective Lagrangian approach. In addition to the contributions from the s-channel nucleon pole, the t-channel D0 exchange, the u-channel exchange and the contact term, we study the contributions from the states with spin-parity JP = 1/2- and 3/2-. The total and differential cross sections of the reaction are predicted. It is found that the contributions of these states give clear peak structures in the total cross sections. Thus, this reaction is another new platform to study the hidden-charm states. It is expected that our model calculation may be tested by future experiments. Supported by Major State Basic Research Development Program in China (2014CB845400), National Natural Science Foundation of China (11475227, 11275235, 11035006) and Chinese Academy of Sciences (Knowledge Innovation Project (KJCX2-EW-N01), Youth Innovation Promotion Association CAS (2016367), Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Y5KF151CJ1)

  14. Quantitative prediction of perceptual decisions during near-threshold fear detection

    NASA Astrophysics Data System (ADS)

    Pessoa, Luiz; Padmala, Srikanth

    2005-04-01

    A fundamental goal of cognitive neuroscience is to explain how mental decisions originate from basic neural mechanisms. The goal of the present study was to investigate the neural correlates of perceptual decisions in the context of emotional perception. To probe this question, we investigated how fluctuations in functional MRI (fMRI) signals were correlated with behavioral choice during a near-threshold fear detection task. fMRI signals predicted behavioral choice independently of stimulus properties and task accuracy in a network of brain regions linked to emotional processing: posterior cingulate cortex, medial prefrontal cortex, right inferior frontal gyrus, and left insula. We quantified the link between fMRI signals and behavioral choice in a whole-brain analysis by determining choice probabilities by means of signal-detection theory methods. Our results demonstrate that voxel-wise fMRI signals can reliably predict behavioral choice in a quantitative fashion (choice probabilities ranged from 0.63 to 0.78) at levels comparable to neuronal data. We suggest that the conscious decision that a fearful face has been seen is represented across a network of interconnected brain regions that prepare the organism to appropriately handle emotionally challenging stimuli and that regulate the associated emotional response. decision making | emotion | functional MRI

  15. Rovibrational Quantum Dynamics of the Methane-Water Dimer

    NASA Astrophysics Data System (ADS)

    Sarka, János; Császár, Attila; Mátyus, Edit

    2017-06-01

    The challenging quantum dynamical description of the CH_4.H_2O complex has been solved variationally to provide theoretical explanation and assignment to the high-resolution spectroscopic measurements of the methane-water dimer carried out some twenty years ago. The computational results are in excellent agreement with the reported experimental transitions and the experimentally observed reversed rovibrational sequences, i.e., formally negative rotational excitation energies, are also obtained in the computations. In order to better understand the origin of these peculiar features in the energy-level spectrum, we studied all four possible combinations of the light and heavy isotopologues of methane and water and analyzed their rovibrational states using two limiting model systems: the rigidly rotating (RR) molecule and the coupled rotor (CR) system corresponding to the coupling of the two rotating monomers. All rovibrational quantum dynamical computations^{a,c} were carried out with rigid monomers and J = 0,1,2 total angular momentum quantum numbers using the fourth-age quantum chemical code GENIUSH and two different methane-water potential energy surfaces (PES). The numerical and formal analysis of the wave functions give insight into a fascinating complex world worth for further theoretical and experimental inquiries. J. Sarka, A. G. Császár, S. C. Althorpe, D. J. Wales and E. Mátyus, Phys. Chem. Chem. Phys. 18, 22816 (2016). L. Dore, R. C. Cohen, C. A. Schmuttenmaer, K. L. Busarow, M. J. Elrod, J. G. Loeser and R. J. Saykally, J. Chem. Phys. 100, 863 (1994). J. Sarka, A. G. Császár and E. Mátyus, Phys. Chem. Chem. Phys. accepted for publication (2017).} E. Mátyus, G. Czakó and A. G. Császár, J. Chem. Phys. 130, 134112 (2009). C. Fábri, E. Mátyus and A. G. Császár, J. Chem. Phys. 134, 074105 (2011). O. Akin-Ojo and K. Szalewicz, J. Chem. Phys. 123, 134311 (2005). C. Qu, R. Conte, P. L. Houston and J. M. Bowman, Phys. Chem. Chem. Phys. 17, 8172 (2015).

  16. Precision Measurement of Electroproduction of pi0 near Threshold

    SciTech Connect

    Chirapatpimol, Khem

    2012-05-01

    Electromagnetic production of neutral pions near threshold is the most basic, lowest energy reaction in which a new hadron is created. The electromagnetic interaction is well understood so measurements of this reaction can yield direct insight into the hadronic production mechanism. During the past three decades there have been many developments in both the measurement and theory of threshold pion production, starting with measurements of photo-production at Saclay in 1986 and at Mainz in 1990. These measurements indicated a surprising discrepancy with so-called Low Energy Theorems (LETs) which are based on quite fundamental symmetries and considerations. Chiral Perturbation Theory (ChPT) is an effective field theoretic description of the nuclear force which contains the underlying symmetries of the force but deals with nucleons and pions rather than quarks and gluons. It has the advantage of being applicable at low energies but requires tuning some parameters to experimental data. Once these parameters have been determined ChPT predicts how the reaction should behave as a function of the kinematic variable. When applied to the reaction, p(γ,π0)p, near threshold it explained the discrepancy with the LETs and made predictions for electroproduction, p(e,e'p)π 0. Electroproduction measurements at Mainz in the 1990's showed a clear discrepancy with these predictions of ChPT; with parameters determined from one set of kinematics the data for a second set lay far from the predicted value. However, recently completed measurements at Mainz disagreed with their previous measurements. In the experiment presented here, measurements of neutral pion electroproduction,p(e,e'p)π0, were made in bins of momentum transfer, Q2, between Q2 = 0.05 [GeV/c]2 and Q2 = 0.15 [GeV/c]0 and of center-of-mass energy, W, between 0 ≤ W ≤ 30 MeV (above threshold). The experiment was performed in Hall A

  17. Near-Threshold Measurement of γn --> pπ- at MAX-lab

    NASA Astrophysics Data System (ADS)

    O'Rielly, Grant; MAX-TAGG Collaboration

    2011-10-01

    One of the important questions in nuclear science is to describe the properties of the nucleon using the framework provided by QCD. Pion photoproduction is one process where both experiment and theory can produce valid and useful results. Consequently, high-quality measurements of this fundamental process can be used to test the predictions of approaches such as chiral effective-field theories and dispersion relations, as well as provide additional data for the SAID and MAID partial-wave analyses. The Photon Tagging Facility at MAX-lab in Lund, Sweden is uniquely suited to perform measurements of pion photoproduction at energies between threshold and the Δ-resonance. The MAX-TAGG collaboration is undertaking a comprehensive program to investigate the γp --> nπ+ , γn --> pπ- and, eventually, γn --> nπ0 channels to complement the existing large data set on the γp --> pπ0 channel. The first measurement of the γn --> pπ- channel has just been completed. Using a LD2 target and the reaction γd --> ppπ- , the π- is captured on another deuteron creating a high-energy γ-ray. These γ-rays were detected using three very large NaI spectrometers. These new near-threshold data will be used to better evaluate the threshold E0+(π-) amplitude, which can be compared with the predictions from Chiral Perturbation Theory and other quark-based theories. Initial results from this measurement will be presented.

  18. Near-threshold incoherent ϕ photoproduction on the deuteron: Searching for traces of a resonance

    NASA Astrophysics Data System (ADS)

    Kiswandhi, Alvin; Yang, Shin Nan; Dong, Yu Bing

    2016-07-01

    We study the near-threshold incoherent ϕ photoproduction on the deuteron based on a model of γ N →ϕ N , consisting of Pomeron, (π ,η ) exchanges, and a JP=3 /2- resonance, which describes the low-energy γ p →ϕ p LEPS data well, including the peak in the forward differential cross section. The calculation is done up to double rescatterings, with the spin dependence of the elementary γ N →ϕ N amplitude retained throughout the calculation. The Fermi motion and final-state interactions (FSIs) are all properly treated as prescribed by realistic nucleon-nucleon interaction. The couplings of the resonance to γ n and ϕ n channels are estimated with the help of a constituent quark model. The main features of the LEPS and CLAS data are described reasonably well except for some quantitative discrepancies at very low energies and low-momentum-transfer regions. It is found that contributions of Fermi motion, p n FSI, and resonance are all indispensable in bridging the differences between the single-scattering results and the data. The off-shell rescattering is found to be important because it cancels out a large portion of the on-shell contribution. The discrepancies at low-momentum-transfer regions might be related to the binning size of the data. No peak is found to be associated with the weak resonance because it gets smeared out by the Fermi motion and FSI with the deuterium target. The problem at very-low-energy regions hints at the possible contributions from other mechanisms and should be investigated in depth with the use of recent high-statistics γ p →ϕ p data from CLAS.

  19. Mechanical resonance enhances the sensitivity of the vibrissa sensory system to near-threshold stimuli.

    PubMed

    Andermann, M L; Moore, C I

    2008-10-15

    The representation of high-frequency sensory information is a crucial problem faced by the nervous system. Rodent facial vibrissae constitute a high-resolution sensory system, capable of discriminating and detecting subtle changes in tactual input. During active sensing, the mechanical properties of vibrissae may play a key role in filtering sensory information and translating it into neural activity. Previous studies have shown that rat vibrissae resonate, conferring frequency specificity to trigeminal ganglion (NV) and primary somatosensory cortex (SI) neurons during suprathreshold sensory stimulation. In addition to frequency specificity, a further potential impact of vibrissa resonance is enhancement of sensitivity to near-threshold stimuli through signal amplification. To examine the effect of resonance on peri-threshold inputs (

  20. Rovibrational product state distribution for inelastic H+D2 collisions.

    PubMed

    Pomerantz, Andrew E; Ausfelder, Florian; Zare, Richard N; Juanes-Marcos, Juan Carlos; Althorpe, Stuart C; Sáez Rábanos, V; Aoiz, F J; Bañares, L; Castillo, J F

    2004-10-08

    Experimental measurements of rovibrational product state distributions for the inelastic scattering process H + D2(nu=0,j)-->H + D2(nu' = 1,2,j') are presented and compared with the results of quasiclassical and quantum mechanical calculations. Agreement between theory and experiment is almost quantitative. Two subtle trends are found: the relative amount of energy in product rotational excitation decreases slightly with increasing collision energy and increases slightly with increasing product vibrational excitation. These trends are the reverse of what has been found for reactive scattering in which the opposite trends are much more pronounced.

  1. Experimental and Finite Element Modeling of Near-Threshold Fatigue Crack Growth for the K-Decreasing Test Method

    NASA Technical Reports Server (NTRS)

    Smith, Stephen W.; Seshadri, Banavara R.; Newman, John A.

    2015-01-01

    The experimental methods to determine near-threshold fatigue crack growth rate data are prescribed in ASTM standard E647. To produce near-threshold data at a constant stress ratio (R), the applied stress-intensity factor (K) is decreased as the crack grows based on a specified K-gradient. Consequently, as the fatigue crack growth rate threshold is approached and the crack tip opening displacement decreases, remote crack wake contact may occur due to the plastically deformed crack wake surfaces and shield the growing crack tip resulting in a reduced crack tip driving force and non-representative crack growth rate data. If such data are used to life a component, the evaluation could yield highly non-conservative predictions. Although this anomalous behavior has been shown to be affected by K-gradient, starting K level, residual stresses, environmental assisted cracking, specimen geometry, and material type, the specifications within the standard to avoid this effect are limited to a maximum fatigue crack growth rate and a suggestion for the K-gradient value. This paper provides parallel experimental and computational simulations for the K-decreasing method for two materials (an aluminum alloy, AA 2024-T3 and a titanium alloy, Ti 6-2-2-2-2) to aid in establishing clear understanding of appropriate testing requirements. These simulations investigate the effect of K-gradient, the maximum value of stress-intensity factor applied, and material type. A material independent term is developed to guide in the selection of appropriate test conditions for most engineering alloys. With the use of such a term, near-threshold fatigue crack growth rate tests can be performed at accelerated rates, near-threshold data can be acquired in days instead of weeks without having to establish testing criteria through trial and error, and these data can be acquired for most engineering materials, even those that are produced in relatively small product forms.

  2. Measurement of the reaction C({nu}{sub mu},{mu}{sup {minus}})X near threshold

    SciTech Connect

    Federspiel, F.J.; LSND Collaboration

    1994-12-31

    Using the decay-in-flight {nu}{sub {mu}} beam from the Los Alamos Meson Physics Facility and a massive liquid scintillator neutrino detector (LSND), the reaction C({nu}{sub {mu}},{mu}{sup {minus}})X has been studied near threshold. Preliminary results for the visible energy distribution of the final state and the flux integrated cross section are presented and compared with the results of several nuclear model calculations.

  3. Interactions between auditory 'what' and 'where' pathways revealed by enhanced near-threshold discrimination of frequency and position.

    PubMed

    Tardif, Eric; Spierer, Lucas; Clarke, Stephanie; Murray, Micah M

    2008-03-07

    Partially segregated neuronal pathways ("what" and "where" pathways, respectively) are thought to mediate sound recognition and localization. Less studied are interactions between these pathways. In two experiments, we investigated whether near-threshold pitch discrimination sensitivity (d') is altered by supra-threshold task-irrelevant position differences and likewise whether near-threshold position discrimination sensitivity is altered by supra-threshold task-irrelevant pitch differences. Each experiment followed a 2 x 2 within-subjects design regarding changes/no change in the task-relevant and task-irrelevant stimulus dimensions. In Experiment 1, subjects discriminated between 750 Hz and 752 Hz pure tones, and d' for this near-threshold pitch change significantly increased by a factor of 1.09 when accompanied by a task-irrelevant position change of 65 micros interaural time difference (ITD). No response bias was induced by the task-irrelevant position change. In Experiment 2, subjects discriminated between 385 micros and 431 micros ITDs, and d' for this near-threshold position change significantly increased by a factor of 0.73 when accompanied by task-irrelevant pitch changes (6 Hz). In contrast to Experiment 1, task-irrelevant pitch changes induced a response criterion bias toward responding that the two stimuli differed. The collective results are indicative of facilitative interactions between "what" and "where" pathways. By demonstrating how these pathways may cooperate under impoverished listening conditions, our results bear implications for possible neuro-rehabilitation strategies. We discuss our results in terms of the dual-pathway model of auditory processing.

  4. Nonequilibrium shock-heated nitrogen flows using a rovibrational state-to-state method.

    PubMed

    Panesi, M; Munafò, A; Magin, T E; Jaffe, R L

    2014-07-01

    A rovibrational collisional model is developed to study the internal energy excitation and dissociation processes behind a strong shock wave in a nitrogen flow. The reaction rate coefficients are obtained from the ab initio database of the NASA Ames Research Center. The master equation is coupled with a one-dimensional flow solver to study the nonequilibrium phenomena encountered in the gas during a hyperbolic reentry into Earth's atmosphere. The analysis of the populations of the rovibrational levels demonstrates how rotational and vibrational relaxation proceed at the same rate. This contrasts with the common misconception that translational and rotational relaxation occur concurrently. A significant part of the relaxation process occurs in non-quasi-steady-state conditions. Exchange processes are found to have a significant impact on the relaxation of the gas, while predissociation has a negligible effect. The results obtained by means of the full rovibrational collisional model are used to assess the validity of reduced order models (vibrational collisional and multitemperature) which are based on the same kinetic database. It is found that thermalization and dissociation are drastically overestimated by the reduced order models. The reasons of the failure differ in the two cases. In the vibrational collisional model the overestimation of the dissociation is a consequence of the assumption of equilibrium between the rotational energy and the translational energy. The multitemperature model fails to predict the correct thermochemical relaxation due to the failure of the quasi-steady-state assumption, used to derive the phenomenological rate coefficient for dissociation.

  5. High Precision Rovibrational Spectroscopy of OH+

    NASA Astrophysics Data System (ADS)

    Markus, Charles R.; Hodges, James N.; Perry, Adam J.; Kocheril, G. Stephen; Müller, Holger S. P.; McCall, Benjamin J.

    2016-02-01

    The molecular ion OH+ has long been known to be an important component of the interstellar medium. Its relative abundance can be used to indirectly measure cosmic ray ionization rates of hydrogen, and it is the first intermediate in the interstellar formation of water. To date, only a limited number of pure rotational transitions have been observed in the laboratory making it necessary to indirectly calculate rotational levels from high-precision rovibrational spectroscopy. We have remeasured 30 transitions in the fundamental band with MHz-level precision, in order to enable the prediction of a THz spectrum of OH+. The ions were produced in a water cooled discharge of O2, H2, and He, and the rovibrational transitions were measured with the technique Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy. These values have been included in a global fit of field free data to a 3Σ- linear molecule effective Hamiltonian to determine improved spectroscopic parameters which were used to predict the pure rotational transition frequencies.

  6. Rovibrational transitions of H2 by collision with H+ at high temperature

    NASA Astrophysics Data System (ADS)

    González-Lezana, T.; Honvault, P.

    2017-01-01

    The H+ +H2 reaction is studied by means of both exact and statistical quantum methods. Integral cross sections for processes initiated with rotationally excited H2(v, j = 1) to produce molecular hydrogen in its rotational ground state are reported up to a value of the collision energy of 3 eV. Rate constants for state-to-state transitions between different H2 rovibrational states are calculated up to 3000 K. Special emphasis is made on ortho/para conversion processes in which the parity j of the H2(j) states changes.

  7. Near-threshold continuum structure and the dissociation energies of H[sub 2], HD, and D[sub 2

    SciTech Connect

    Eyler, E.E.; Melikechi, N. )

    1993-07-01

    Using laser double-resonance spectroscopy, we have studied the second dissociation limit of all three stable isotopic variants of molecular hydrogen. Just above threshold, the vibrational continuum exhibits considerable fine-grained structure, differing greatly between isotopes because of varying nonadiabatic couplings between the [ital B], [ital B][prime], and [ital C] states. Significantly improved values of the dissociation energies are obtained from the continuum onsets. We also report preliminary investigations of atomic 2[ital S]:2[ital P] branching ratios very near threshold.

  8. On peculiarities of near-threshold initiation of powder density explosive by air shock wave and by solid impactor

    NASA Astrophysics Data System (ADS)

    Kashkarov, AO; Ershov, AP; Pruuel, ER

    2016-10-01

    The features of near-threshold mode of initiating by gas-tight piston and high- enthalpy gas flow was evaluated for a powder density explosive PETN. Both methods lead to the development of detonation in about 10 μs time. The synchrotron radiation diagnostics have shown that the initial stages of the process were significantly different, that diversity being caused by the influence of the gas flow in the pores of the charge. In this work, the effect of the gas flow on the mode of initiation was studied experimentally.

  9. Simultaneous manipulation and observation of multiple ro-vibrational eigenstates in solid para-hydrogen

    NASA Astrophysics Data System (ADS)

    Katsuki, Hiroyuki; Ohmori, Kenji

    2016-09-01

    We have experimentally performed the coherent control of delocalized ro-vibrational wave packets (RVWs) of solid para-hydrogen (p-H2) by the wave packet interferometry (WPI) combined with coherent anti-Stokes Raman scattering (CARS). RVWs of solid p-H2 are delocalized in the crystal, and the wave function with wave vector k ˜ 0 is selectively excited via the stimulated Raman process. We have excited the RVW twice by a pair of femtosecond laser pulses with delay controlled by a stabilized Michelson interferometer. Using a broad-band laser pulse, multiple ro-vibrational states can be excited simultaneously. We have observed the time-dependent Ramsey fringe spectra as a function of the inter-pulse delay by a spectrally resolved CARS technique using a narrow-band probe pulse, resolving the different intermediate states. Due to the different fringe oscillation periods among those intermediate states, we can manipulate their amplitude ratio by tuning the inter-pulse delay on the sub-femtosecond time scale. The state-selective manipulation and detection of the CARS signal combined with the WPI is a general and efficient protocol for the control of the interference of multiple quantum states in various quantum systems.

  10. Near threshold dynamics and dissociation energy of the reaction H 2CO → HCO + H

    NASA Astrophysics Data System (ADS)

    Terentis, Andrew C.; Kable, Scott H.

    1996-08-01

    The state-to-state dynamics of the gas phase reaction H 2CO ( v, J, Ka, Kc) + hv → H + HCO( v, N, S, Ka, Kc) have been explored in a supersonic free jet. Seven rotational states within the 2 14 3 vibrational level of H 2CO were excited and the population distribution of the HCO ( v = 0, N, S, Ka, Kc) product states measured. The distributions are constrained severely by the available energy in the reaction with the lowest H 2CO state producing HCO in only three rotational states. Careful matching of the H 2CO and HCO energy levels leads to an estimate of the dissociation energy of the above reaction of 30328.5 ± 0.5 cm -, which lead us to an estimate of the standard heat of formation of the formyl radical of ΔHf0 = 42.5 ± 0.5 kJ mol -1.

  11. Near-threshold photoelectron angular distributions from two-photon resonant photoionization of He

    NASA Astrophysics Data System (ADS)

    O'Keeffe, P.; Mihelič, A.; Bolognesi, P.; Žitnik, M.; Moise, A.; Richter, R.; Avaldi, L.

    2013-01-01

    Two-photon resonant photoionization of helium is investigated both experimentally and theoretically. Ground state helium atoms are excited to the 1s4p, 1s5p and 1s6p 1P states by synchrotron radiation and ionized by a synchronized infrared pulsed picosecond laser. The photoelectron angular distributions of the emitted electrons are measured using a velocity map imaging (VMI) spectrometer. The measured asymmetry parameters of the angular distribution allow the phase differences and the ratios of the dipole matrix elements of the 1sɛs and 1sɛd channels to be determined. The experimental results agree with the calculated values obtained in a configuration-interaction calculation with a Coulomb-Sturmian basis set. The effects of the radiative decay of the intermediate state and the static electric field of the VMI spectrometer on the measurements are discussed.

  12. Near-threshold J/Ψ production in proton-nucleus collisions

    NASA Astrophysics Data System (ADS)

    Kiselev, Yu. T.; Paryev, E. Ya.; Zaitsev, Yu. M.

    2014-12-01

    We study the J/Ψ production from nuclei near the kinematic threshold within the collision model, based on the nuclear spectral function, for incoherent primary proton-nucleon charmonium creation processes. The model takes into account the initial proton and final J/Ψ absorption, target nucleon binding and Fermi motion, the formation length of J/Ψ mesons as well as the effect of their nuclear mean-field potential on these processes. We calculate the A-dependences of the absolute and relative (transparency ratio) charmonium yields as well as its excitation function within the different scenarios for the J/ΨN absorption cross-section, for the J/Ψ formation length and for J/Ψ in-medium modification. We demonstrate that the former observables, on the one hand, are not practically affected by the charmonium formation length effects and, on the other hand, they are appreciably sensitive to the genuine J/ΨN absorption cross-section at beam energies of interest, which means that these observables can be useful to help determine the above cross-section from the comparison of the results of our calculations with the future data from the CBM experiment at FAIR-the upcoming accelerator facility at GSI-Darmstadt, Germany. We also show that the excitation function for J/Ψ subthreshold production in pA reactions, reveals some sensitivity to adopt its in-medium modification scenarios. Therefore, such observable may be an important tool to get valuable information on the charmonium in-medium properties.

  13. Near-threshold resonances in electron elastic scattering cross sections for Au and Pt atoms: identification of electron affinities

    NASA Astrophysics Data System (ADS)

    Msezane, A. Z.; Felfli, Z.; Sokolovski, D.

    2008-05-01

    The recent Regge-pole methodology has been employed together with a Thomas-Fermi type potential which incorporates the vital core-polarization interaction to investigate the near-threshold electron attachment in Au and Pt as Regge resonances. The resultant stable negative ion states are found to have the discernible characteristic of very small imaginary parts of the Regge poles, which translate into long-lived resonances. The near-threshold electron elastic total cross sections are characterized by multiple resonances from which we extract the electron affinity (EA) values through the scrutiny of the imaginary part of the relevant complex angular momentum. For the Au- and Pt- negative ions the extracted binding energies of 2.262 eV and 2.163 eV, respectively are in excellent agreement with the most recently measured EA values for Au and Pt. Ramsauer-Townsend minima, shape resonances and the Wigner threshold behaviour are identified in both Au- and Pt- ions.

  14. Resonances in Near-Threshold Electron Elastic Scattering Cross Sections for Au and Pt: Identification of Electron Affinities.

    NASA Astrophysics Data System (ADS)

    Felfli, Z.; Msezane, A. Z.; Sokolovski, D.

    2008-05-01

    The near-threshold electron attachment in Au and Pt atoms is investigated as Regge resonances using our recent Regge-pole methodology [1] together with a Thomas-Fermi potential which incorporates the crucial core-polarization interaction. The resultant stable negative ion states are found to have the discernable characteristic of very small imaginary parts of the Regge poles, which translates into long-lived resonances. The near-threshold electron elastic total cross sections for both Au and Pt are characterized by multiple resonances from which we extract the electron affinity (EA) values through the scrutiny of the imaginary part of the relevant complex angular momentum. For Au^- and Pt^- the extracted binding energies of 2.262 eV and 2.163 eV, respectively, are in excellent agreement with the most recently measured EA values for Au [2] and Pt [3]. Ramsauer-Townsend minima, shape resonances and the Wigner threshold behavior are identified in both Au^- and Pt^- ions.[1] D. Sokolovski et al, Phys. Rev. A 76, 012705 (2007)[2] H. Hotop and W. C. Lineberger, J. Chem. Ref. Data 14, 731 (1985)[3] R. C. Bilodeau et al, Phys. Rev. A 61, 012505 (1999)

  15. The influence of s states near threshold on the structure of light nuclei

    NASA Astrophysics Data System (ADS)

    Hoffman, Calem

    2015-10-01

    A recent work identified the role of neutron s states, and their proximity to the neutron separation threshold, on the ordering of the 1s1 / 2 and 0d5 / 2 single-particle levels in light nuclei. A simple Woods-Saxon potential was used to reproduce the systematic data available for these two levels with great success by accounting for the s state binding energy. This talk will explore other noticeable trends in light nuclei involving neutron s states and utilizing simple potential models determine the role binding energy plays. The trends and calculations will aim to provide descriptions of data and predictions of yet to be found two-particle two-hole excited states in N = 8 and 10 nuclei ranging from Z = 4-9, as well as the energies of mirror states in neutron deficient Al and Na isotopes. Results will be compared with state-of-the-art calculations. Possible future measurements capable of probing these predictions will be discussed as well. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract Number DE-AC02-06CH11357.

  16. Low-lying quasibound rovibrational states of H2 16O**

    NASA Astrophysics Data System (ADS)

    Szidarovszky, Tamás; Császár, Attila G.

    2013-08-01

    A complex coordinate scaling (CCS) method is described allowing the quantum chemical computation of quasibound (also called resonance or metastable) rovibrational states of strongly bound triatomic molecules. The molecule chosen to test the method is H2 16O, for which an accurate global potential energy surface, a previous computation of a few resonance states via the complex absorbing potential (CAP) method, and some Feshbach (J = 0, where J is the quantum number characterising overall rotations of the molecule) and shape (J ≠ 0) resonances measured via a state-selective, triple-resonance technique are all available. Characterisation of the computed resonance states is performed via probability density plots based on CCS rovibrational wavefunctions. Such plots provide useful details about the physical nature of the resonance states. Based on the computations and the resonance plots, the following useful facts about the resonance states investigated are obtained: (a) Feshbach resonances are formed by accumulation of a large amount of energy in either the non-dissociative bending or symmetric streching modes, excitations by more than five quanta are not uncommon; (b) there are several resonance states with low and medium bending excitation, the latter are different from the states observed somewhat below dissociation by the same triple-resonance technique; (c) several types of dissociation bahavior can be identified, varying greatly among the states; (d) several pairs of J = 0 and J = 1 Feshbach resonance states can be identified which differ by rigid-rotor type energies; and (e) the lifetimes of the assigned J = 1 rovibrational Feshbach resonances are considerably longer than the lifetimes of their J = 0 vibrational counterparts.

  17. Potential energy surface and rovibrational energy levels of the H2-CS van der Waals complex.

    PubMed

    Denis-Alpizar, Otoniel; Stoecklin, Thierry; Halvick, Philippe; Dubernet, Marie-Lise; Marinakis, Sarantos

    2012-12-21

    Owing to its large dipole, astrophysicists use carbon monosulfide (CS) as a tracer of molecular gas in the interstellar medium, often in regions where H(2) is the most abundant collider. Predictions of the rovibrational energy levels of the weakly bound complex CS-H(2) (not yet observed) and also of rate coefficients for rotational transitions of CS in collision with H(2) should help to interpret the observed spectra. This paper deals with the first goal, i.e., the calculation of the rovibrational energy levels. A new four-dimensional intermolecular potential energy surface for the H(2)-CS complex is presented. Ab initio potential energy calculations were carried out at the coupled-cluster level with single and double excitations and a perturbative treatment of triple excitations, using a quadruple-zeta basis set and midbond functions. The potential energy surface was obtained by an analytic fit of the ab initio data. The equilibrium structure of the H(2)-CS complex is found to be linear with the carbon pointing toward H(2) at the intermolecular separation of 8.6 a(o). The corresponding well depth is -173 cm(-1). The potential was used to calculate the rovibrational energy levels of the para-H(2)-CS and ortho-H(2)-CS complexes. The present work provides the first theoretical predictions of these levels. The calculated dissociation energies are found to be 35.9 cm(-1) and 49.9 cm(-1), respectively, for the para and ortho complexes. The second virial coefficient for the H(2)-CS pair has also been calculated for a large range of temperature. These results could be used to assign future experimental spectra and to check the accuracy of the potential energy surface.

  18. Cross section and analyzing power of {rvec p}p{r_arrow}pn{pi}{sup +} near threshold

    SciTech Connect

    Faeldt, G.; Wilkin, C.

    1997-10-01

    The cross section and analyzing power of the {rvec p}p{r_arrow}pn{pi}{sup +} reaction near threshold are estimated in terms of data obtained from the {rvec p}p{r_arrow}d{pi}{sup +} and pp{r_arrow}pp{pi}{sup 0} reactions. A simple final state interaction theory is developed which depends weakly upon the form of the pion-production operator and includes some Coulomb corrections. Within the uncertainties of the model and the input data, the approach reproduces well the measured energy dependence of the total cross section and the proton analyzing power at a fixed pion center-of-mass angle of 90{degree}, from threshold to T{sub p}=330 MeV. The variation of the differential cross section with pion angle is also very encouraging. {copyright} {ital 1997} {ital The American Physical Society}

  19. Rovibrational CO analysis in PDR models

    NASA Astrophysics Data System (ADS)

    Stancil, Phillip C.; Cumbee, Renata; Zhang, Ziwei; Walker, Kyle M.; Yang, Benhui; Ferland, Gary J.

    2016-01-01

    CO is one of the most important molecules in the interstellar medium and in photodissociation regions (PDRs). Most of the extragalactic non-stellar IR to submm CO emission originates in PDRs. (Hollenbach & Tielens 1999). Pure rotational CO lines have been previously used in PDR models to provide density, temperature, and other diagnostics. However, for environments exposed to intense UV radiation, CO vibrational levels become significantly populated. Given new calculations of rovibrational collisional rate coefficients for CO-H (Walker et al. 2015, Song et al. 2015) and CO-H2 (Yang et al. 2015), we explore their effects in standard Cloudy PDR (Ferland et al. 2013) and Radex (van der Tak et al. 2007) models. In particular, CO vibrational transitions due to H2 collisions are studied for the first time using reliable full-dimensional CO-H2 collisional data.Ferland, G. J., et al. 2013, Rev. Mex. Astron. y Astrof., 49, 137Hollenbach, D. J. & Tielens, A. G. G. M. 1999, RMP, 71, 173Song, L., et al. 2015, ApJ, in pressvan der Tak, F. F. S, et al. 2007, A&A, 468, 627Walker, K. M., et al. 2015, ApJ, 811, 27Yang, B., et al. 2015, Nature Comm., 6, 6629This work was supported in part by NASA grants NNX12AF42G and NNX15AI61G.

  20. Optimization parameters for BDE in BNCT using near threshold 7Li(p,n)7Be direct neutrons.

    PubMed

    Bengua, Gerard; Kobayashi, Tooru; Tanaka, Kenichi; Nakagawa, Yoshinobu

    2004-11-01

    The dose contribution of (10)B(n,alpha)(7)Li reaction in BNCT using near threshold (7)Li(p,n)(7)Be direct neutrons can be increased through the use of materials referred to as boron-dose enhancers (BDE). In this paper, possible BDE optimization criteria were determined from the characteristics of candidate BDE materials namely (C(2)H(4))(n), (C(2)H(3)F)(n), (C(2)H(2)F(2))(n), (C(2)HF(3))(n), (C(2)D(4))(n), (C(2)F(4))(n), beryllium metal, graphite, D(2)O and (7)LiF. The treatable protocol depth (TPD) was used as the assessment index for evaluating the effect of these materials on the dose distribution in a medium undergoing BNCT using near threshold (7)Li(p,n)(7)Be direct neutrons. The maximum TPD (TPD(max)) did not exhibit an explicit dependence on material type as evidenced by its small range and arbitrary variations. The dependence of TPD on BDE thickness was influenced by the BDE material used as indicated by the sharply peaked TPD versus BDE thickness curves for materials with hydrogen compared to the broader curves obtained for those without hydrogen. The BDE thickness required to achieve TPD(max) (BDE(TPD(max))) were also found to be thinner for materials with hydrogen. The TPD(max), the dependence of TPD on BDE thickness, and the BDE(TPD(max)) were established as appropriate BDE optimization parameters. Based on these criteria and other practical considerations, the suitable choice as BDE among the candidate materials considered in this study for treatments involving tumors located at shallow depths would be (C(2)H(4))(n) while beryllium metal was judged as more appropriate for treatment of deep-seated tumors.

  1. Rovibrational Wave-Packet Dispersion during Femtosecond Laser Filamentation in Air

    SciTech Connect

    Odhner, J. H.; Romanov, D. A.; Levis, R. J.

    2009-08-14

    An impulsive, femtosecond filament-based Raman technique producing high quality Raman spectra over a broad spectral range (1554.7-4155 cm{sup -1}) is presented. The temperature of gas phase molecules can be measured by temporally resolving the dispersion of impulsively excited vibrational wave packets. Application to laser-induced filamentation in air reveals that the initial rovibrational temperature is 300 K for both N{sub 2} and O{sub 2}. The temperature-dependent wave-packet dynamics are interpreted using an analytic anharmonic oscillator model. The wave packets reveal a 1/e dispersion time of 3.9 ps for N{sub 2} and 2.8 ps for O{sub 2}. Pulse self-compression of temporal features to 8 fs within the filament is directly measured by impulsive vibrational excitation of H{sub 2}.

  2. An accurate global potential energy surface, dipole moment surface, and rovibrational frequencies for NH(3).

    PubMed

    Huang, Xinchuan; Schwenke, David W; Lee, Timothy J

    2008-12-07

    A global potential energy surface (PES) that includes short and long range terms has been determined for the NH(3) molecule. The singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations and the internally contracted averaged coupled-pair functional electronic structure methods have been used in conjunction with very large correlation-consistent basis sets, including diffuse functions. Extrapolation to the one-particle basis set limit was performed and core correlation and scalar relativistic contributions were included directly, while the diagonal Born-Oppenheimer correction was added. Our best purely ab initio PES, denoted "mixed," is constructed from two PESs which differ in whether the ic-ACPF higher-order correlation correction was added or not. Rovibrational transition energies computed from the mixed PES agree well with experiment and the best previous theoretical studies, but most importantly the quality does not deteriorate even up to 10 300 cm(-1) above the zero-point energy (ZPE). The mixed PES was improved further by empirical refinement using the most reliable J=0-2 rovibrational transitions in the HITRAN 2004 database. Agreement between high-resolution experiment and rovibrational transition energies computed from our refined PES for J=0-6 is excellent. Indeed, the root mean square (rms) error for 13 HITRAN 2004 bands for J=0-2 is 0.023 cm(-1) and that for each band is always

  3. Structural, vibrational, and rovibrational analysis of tetrafluoroethylene.

    PubMed

    Medcraft, C; Fuss, W; Appadoo, D R T; McNaughton, D; Thompson, C D; Robertson, E G

    2012-12-07

    High resolution FTIR spectra of (13)C enriched tetrafluoroethylene (C(2)F(4)) were measured at 150 K at the Australian Synchrotron. Rovibrational transitions were assigned in the a-type symmetric and b-type antisymmetric CF(2) stretches of (12)C(13)CF(4) and (13)C(2)F(4) near 1170 cm(-1) and 1300 cm(-1), respectively. Ground vibrational state spectroscopic constants for both molecules were determined in addition to the upper state constants for ν(11) and ν(9) of (13)C(2)F(4) and ν(11), ν(2)+ν(6), and ν(5) of (12)C(13)CF(4). The ground state constants, along with those determined for the (12)C(2)F(4) isotopologue from previously published data, were used to determine a semi-experimental r(e) structure r(CC) = 132.36 ± 0.37 pm, r(CF) = 131.11 ± 0.23 pm, α(FCC) = 123.3 ± 0.3° in excellent agreement with ab initio structures. Lower resolution FTIR spectra were measured between 100 and 5000 cm(-1) at room temperature and band centres obtained for all modes of the three isotopologues; although only 5 out of 12 modes in (12)C(2)F(4) and (13)C(2)F(4) are infrared (IR) active, the others were inferred from combination and hot-band positions. A number of modes are observed to be infrared active only in the (12)C(13)CF(4) isotopologue due to its lower symmetry. Most notably, decoupling of the antisymmetric CF(2) motions in the two halves of (12)C(13)CF(4) results in 2 strongly IR active modes that involve motion at one carbon or the other.

  4. Intramolecular Rovibrational Dynamics of Hydrocarbons and Argon

    NASA Astrophysics Data System (ADS)

    McIlroy, Andrew

    This dissertation describes investigations of the intramolecular dynamics of two types of systems: isolated hydrocarbon molecules, and clusters of Ar atoms with an HF molecule. Both are studied via high resolution (0.001 cm^{-1}) infrared (IR) laser spectroscopy in a slit supersonic expansion. The slit expansion provides a cold (T = 3-15 K) source of isolated gas phase molecules or complexes with sufficient pathlength to carry out IR laser absorption experiments. Furthermore, probing the expansion parallel to the slit produces Doppler broadening up to a factor of ten below that found at room temperature facilitating high resolution, state specific experiments. In the hydrocarbon v = 1 >=ts 0 CH stretch spectra, the vibrational mixing ultimately responsible for intramolecular vibrational energy redistribution (IVR) is elucidated from the observation of splitting of the individual rovibrational transitions; this is due to coupling of the CH stretch to the bath of combination and overtone states. The repetition of qualitative patterns in these data suggest that in some cases individual functional groups within a molecule may control IVR rates largely independent of the specific details of the molecule. For example, vibrational coupling of acetylenic CH stretches is shown to produce similar relaxation rates in molecules whose vibrational state densities vary by almost three orders of magnitude. The studies of Ar_{rm n}HF complexes, n = 1-4, focus on the transition from a free, gas phase HF molecule to a "solvated" HF in an Ar matrix. Models describing the observed red shifting of the HF vibration with the sequential addition of Ar atoms are investigated. Furthermore, these multibody clusters provide the opportunity to test the approximation of the potential energy surfaces (PES) of weakly bound (< 1000 cm^{-1}) systems with sums of two-body potentials. Initial calculations and experiments suggest that significant discrepancies exist between the true PES and the

  5. Rovibrational energy transfer and dissociation in O2-O collisions.

    PubMed

    Andrienko, Daniil A; Boyd, Iain D

    2016-03-14

    A set of state-specific transition rates for each rovibrational level is generated for the O2(X(3)Σ(g)(-))-O(3)P system using the quasi-classical trajectory method at temperatures observed in hypersonic flows. A system of master equations describes the relaxation of the rovibrational ensemble to thermal equilibrium under ideal heat bath conditions at a constant translational temperature. Vibrational and rotational relaxation times, obtained from the average internal energies, exhibit a pattern inherent in a chemically reactive collisional pair. An intrinsic feature of the O3 molecular system with a large attractive potential is a weak temperature dependence of the rovibrational transition rates. For this reason, the quasi-steady vibrational and rotational temperatures experience a maximum at increasing translational temperature. The energy rate coefficients, that characterize the average loss of internal energy due to dissociation, quickly diminish at high temperatures, compared to other molecular systems.

  6. Rovibrational energy transfer and dissociation in O2-O collisions

    NASA Astrophysics Data System (ADS)

    Andrienko, Daniil A.; Boyd, Iain D.

    2016-03-01

    A set of state-specific transition rates for each rovibrational level is generated for the O 2 ( X 3 Σg - ) - O (" separators=" 3 P ) system using the quasi-classical trajectory method at temperatures observed in hypersonic flows. A system of master equations describes the relaxation of the rovibrational ensemble to thermal equilibrium under ideal heat bath conditions at a constant translational temperature. Vibrational and rotational relaxation times, obtained from the average internal energies, exhibit a pattern inherent in a chemically reactive collisional pair. An intrinsic feature of the O3 molecular system with a large attractive potential is a weak temperature dependence of the rovibrational transition rates. For this reason, the quasi-steady vibrational and rotational temperatures experience a maximum at increasing translational temperature. The energy rate coefficients, that characterize the average loss of internal energy due to dissociation, quickly diminish at high temperatures, compared to other molecular systems.

  7. Unstable particles near threshold

    NASA Astrophysics Data System (ADS)

    Chway, Dongjin; Jung, Tae Hyun; Kim, Hyung Do

    2016-07-01

    We explore the physics of unstable particles when the mother particle's mass is approximately the sum of the masses of its daughter particles. In this case, the conventional wave function renormalization factor used for the narrow width approximation is ill-defined. We propose a simple resolution of the problem that allows the use of the narrow width approximation by defining the wave function renormalization factor and the branching ratio in terms of the spectral density. We test new definitions by calculating the cross section in the Higgs portal model and a significant improvement is obtained. Meanwhile, no single decay width can be assigned to the unstable particles and non-exponential decay occurs at all time scales.

  8. Unravelling the dynamical origin of below- and near-threshold harmonic generation of H2+ in an intense NIR laser field.

    PubMed

    Heslar, John; Chu, Shih-I

    2016-11-24

    Recently, the study of near- and below- threshold regime harmonics as a potential source of intense coherent vacuum-ultraviolet radiation has received considerable attention. However, the dynamical origin of these lower harmonics, particularly for the molecular systems, is less understood and largely unexplored. Here we perform the first fully ab initio and high precision 3D quantum study of the below- and near-threshold harmonic generation of molecules in an intense 800-nm near-infrared (NIR) laser field. Combining with a synchrosqueezing transform of the quantum time-frequency spectrum and an extended semiclassical analysis, we explore in-depth the roles of various quantum trajectories, including short- and long trajectories, multiphoton trajectories, resonance-enhanced trajectories, and multiple rescattering trajectories of the below- and near- threshold harmonic generation processes. Our results shed new light on the dynamical origin of the below- and near-threshold harmonic generation and various quantum trajectories for diatomic molecules for the first time.

  9. Unravelling the dynamical origin of below- and near-threshold harmonic generation of H2+ in an intense NIR laser field

    NASA Astrophysics Data System (ADS)

    Heslar, John; Chu, Shih-I.

    2016-11-01

    Recently, the study of near- and below- threshold regime harmonics as a potential source of intense coherent vacuum-ultraviolet radiation has received considerable attention. However, the dynamical origin of these lower harmonics, particularly for the molecular systems, is less understood and largely unexplored. Here we perform the first fully ab initio and high precision 3D quantum study of the below- and near-threshold harmonic generation of molecules in an intense 800-nm near-infrared (NIR) laser field. Combining with a synchrosqueezing transform of the quantum time-frequency spectrum and an extended semiclassical analysis, we explore in-depth the roles of various quantum trajectories, including short- and long trajectories, multiphoton trajectories, resonance-enhanced trajectories, and multiple rescattering trajectories of the below- and near- threshold harmonic generation processes. Our results shed new light on the dynamical origin of the below- and near-threshold harmonic generation and various quantum trajectories for diatomic molecules for the first time.

  10. Rovibrationally inelastic scattering of CN-H2: Full-dimensional close-coupling study

    NASA Astrophysics Data System (ADS)

    Yang, Benhui; Wang, Xiaohong; Stancil, P.; Bowman, J.; Naduvalath, Balakrishnan; Forrey, Robert C.

    2016-01-01

    Rotational and vibrational rate coefficients of CN in collisions with H2 are essential for modeling CN infrared spectra in interstellar gas. We report here full-dimensional potential energy surface (PES) and rovibrational scattering calculations for the CN-H2 collision system.A full-dimensional (6D) PES was calculated using the high-level ab initio CCSD(T)-F12B method. The invariant polynomial method was applied to fit the PES analytically in 6D. Quantum coupled-channel calculations of rotational excitation cross section of CN(j1=4) scattered by para-H2(j2=0, 2) and ortho-H2 (j2=1) were performed for collision energies ranging from 1.0 to 1500 cm-1. State-to-state rate coefficients of CN(j1=4) are computed for H2 rotational states j2=0-2. Comparison of the pure rotational cross sections and rate coefficients were made withprevious available theoretical and experimental results. For the first time we present rovibrational quenching cross sections and rate coefficients of CN in collisions with H2 on the new 6D PES.Work at UGA and Emory are supported by NASA grant NNX12AF42G, at UNLV by NSF Grant PHY-1205838, and at Penn State by NSF Grant PHY-1203228.

  11. A quasi-classical trajectory study of the OH + SO reaction: the role of ro-vibrational energy.

    PubMed

    Pires, W A D; Garrido, J D; Nascimento, M A C; Ballester, M Y

    2014-07-07

    A study of the OH + SO → H + SO2 reaction using a quasi-classical trajectory method is presented with the aim of investigating the role of the ro-vibrational energy of the reactants in the reactivity. The calculations were carried out using a previously reported global potential energy surface for HSO2((2)A). Different initial conditions with one and both reactants ro-vibrationally excited were studied. The reactive cross sections, for each studied combination, are calculated and then fitted to a capture-like model combined with a factor accounting for the recrossing effects. The Vibrational Energy Quantum Mechanical Threshold of the Complex method was used to correct for the zero-point vibrational energy leakage of the classical calculations. State specific and averaged rate constants are reported. The reactivity is affected when ro-vibrational energy of either of the reactants is changed. The present calculations provide a theoretical support for the experimental rate constant for temperatures below 550 K, but fail to account for the significant fall in the observed rate constant upon increasing the temperature above this value.

  12. EEG amplitude spectra before near threshold visual presentations differentially predict detection/omission and short-long reaction time outcomes.

    PubMed

    Achim, André; Bouchard, Julie; Braun, Claude M J

    2013-07-01

    Performance in simple stimulus detection manifests as both probability of detection and speed of signaling detected stimuli. These two dimensions of performance across trials were examined with respect to brain states just prior to stimulus delivery, using near threshold stimuli targeting the magnocellular or the parvocellular visual streams in an attempt to isolate differential perceptual preparation. The EEG amplitude of 12 university students was analyzed in spectral bands from 2 to 50 Hz at 9 bilateral channel pairs in a window covering -450 ms to +50 ms relative to stimulus onset. A hierarchical statistical procedure was applied to control false positive results. EEG power in the 2, 4, 8 and 10 Hz bands was found significantly lower at the F7-F8 channel pair both before detected compared to omitted stimuli and before the fastest compared to slowest reaction time quartiles, with no stimulus type effect. In addition, the 22 and 24 Hz band activity was lower prior to better performance frontally (F3-F4, F7-F8) in reaction time but not in detection, while it was larger centro-parietally (CP1-CP2, P3-P4) in detection but not in reaction times. Spectral analysis thus shows stimulus detection and response speed to depend partly on common and partly on distinct pre-stimulus brain states.

  13. An Empirical Sequence of Disk Gap Opening Revealed by Rovibrational CO

    NASA Astrophysics Data System (ADS)

    Banzatti, A.; Pontoppidan, K. M.

    2015-08-01

    The fundamental rovibrational band of CO near 4.7 μm is a sensitive tracer of the presence and location of molecular gas in the planet-forming region of protoplanetary disks at 0.01-10 AU. We present a new analysis of a high-resolution spectral survey (R ˜ 96,000, or ˜ 3.2 {km} {{{s}}}-1) of CO rovibrational lines from protoplanetary disks spanning a wide range of stellar masses and of evolutionary properties. We find that the CO emission originates in two distinct velocity components. Line widths of both components correlate strongly with disk inclination, as expected for gas in Keplerian rotation. By measuring the line flux ratios between vibrational transitions {F}v=2-1/{F}v=1-0, we find that the two velocity components are clearly distinct in excitation. The broad component ({FWHM}=50-200 {km} {{{s}}}-1) probes the disk region near the magnetospheric accretion radius at ≈ 0.05 AU, where the gas is hot (800-1500 K). The narrow component ({FWHM}=10-50 {km} {{{s}}}-1) probes the disk at larger radii of 0.1-10 AU, where the gas is typically colder (200-700 K). CO excitation temperatures and orbital radii define an empirical temperature-radius relation as a power law with index -0.3 ± 0.1 between 0.05 and 3 AU. The broad CO component, co-spatial with the observed orbital distribution of hot Jupiters, is rarely detected in transitional and Herbig Ae disks, providing evidence for an early dissipation of the innermost disk. An inversion in the temperature profile beyond 3 AU is interpreted as a tracer of a regime dominated by UV pumping in largely devoid inner disks, and may be a signature of the last stage before the disk enters the gas-poor debris phase.

  14. Electronic structure of the polar molecules XF (X: Be, Mg, Ca) with rovibrational and dipole moment calculations

    NASA Astrophysics Data System (ADS)

    El-Kork, Nayla; Abu el kher, Nariman; Korjieh, Farah; Chtay, John Anwar; Korek, Mahmoud

    2017-04-01

    A theoretical investigation for the feasibility of laser-cooling is performed through the calculation of accurate potential energy curves, static dipole moments, spectroscopic constants and rovibrational calculations for 24, 26 and 27 highly excited electronic states for BeF, CaF and MgF molecules respectively. In order to understand the electronic structure of their lowest lying electronic states and to learn the characteristic behavior of their chemical bonding, a high level of calculation is realized by using the complete active space self-consistent field (CASSCF) with multi-reference configuration interaction MRCI method including single and double excitations with Davidson correction (+ Q) for the three considered molecules. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement. Fifty new excited electronic states have been investigated, in the present work, for the first time for the three studied molecules.

  15. Electronic structure of the polar molecules XF (X: Be, Mg, Ca) with rovibrational and dipole moment calculations.

    PubMed

    El-Kork, Nayla; Abu El Kher, Nariman; Korjieh, Farah; Chtay, John Anwar; Korek, Mahmoud

    2017-04-15

    A theoretical investigation for the feasibility of laser-cooling is performed through the calculation of accurate potential energy curves, static dipole moments, spectroscopic constants and rovibrational calculations for 24, 26 and 27 highly excited electronic states for BeF, CaF and MgF molecules respectively. In order to understand the electronic structure of their lowest lying electronic states and to learn the characteristic behavior of their chemical bonding, a high level of calculation is realized by using the complete active space self-consistent field (CASSCF) with multi-reference configuration interaction MRCI method including single and double excitations with Davidson correction (+Q) for the three considered molecules. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement. Fifty new excited electronic states have been investigated, in the present work, for the first time for the three studied molecules.

  16. Photodissociation spectroscopy of stored CH+ ions: Detection, assignment, and close-coupled modeling of near-threshold Feshbach resonances

    NASA Astrophysics Data System (ADS)

    Hechtfischer, Ulrich; Williams, Carl J.; Lange, Michael; Linkemann, Joachim; Schwalm, Dirk; Wester, Roland; Wolf, Andreas; Zajfman, Daniel

    2002-11-01

    We have measured and theoretically analyzed a photodissociation spectrum of the CH+ molecular ion in which most observed energy levels lie within the fine-structure splitting of the C+ fragment and predissociate, and where the observed irregular line shapes and dipole-forbidden transitions indicate that nonadiabatic interactions lead to multichannel dynamics. The molecules were prepared in low rotational levels J''=0-9 of the vibrational ground state X 1Sigma+ (v'')=0 by storing a CH+ beam at 7.1 MeV in the heavy-ion storage ring TSR for up to 30 s, which was sufficient for the ions to rovibrationally thermalize to room temperature by spontaneous infrared emission. The internally cold molecules were irradiated with a dye laser at photon energies between 31 600-33 400 cm-1, and the resulting C+ fragments were counted with a particle detector. The photodissociation cross section displays the numerous Feshbach resonances between the two C+ fine-structure states predicted by theory for low rotation. The data are analyzed in two steps. First, from the overall structure of the spectrum, by identifying branches, and by a Le Roy-Bernstein analysis of level spacings we determine the dissociation energy D0=(32 946.7plus-or-minus1.1) cm-1 (with respect to the lower fine-structure limit) and assign the strongest features to the vibrational levels v'=11-14 of the dipole-allowed A 1Pi state. The majority of the 66 observed resonances cannot be assigned in this way. Therefore, in a second step, the complete spectrum is simulated with a close-coupling model, starting from recent ab initio Born-Oppenheimer potentials. For the long-range induction, dispersion and exchange energies, we propose an analytical expression and derive the C6 coefficients. After a systematic variation of just the vibrational defects of the four Born-Oppenheimer potentials involved, the close-coupling model yields a quantitative fit to the measured cross section in all detail, and is used to assign most of

  17. Theoretical studies of electronically excited states

    SciTech Connect

    Besley, Nicholas A.

    2014-10-06

    Time-dependent density functional theory is the most widely used quantum chemical method for studying molecules in electronically excited states. However, excited states can also be computed within Kohn-Sham density functional theory by exploiting methods that converge the self-consistent field equations to give excited state solutions. The usefulness of single reference self-consistent field based approaches for studying excited states is demonstrated by considering the calculation of several types of spectroscopy including the infrared spectroscopy of molecules in an electronically excited state, the rovibrational spectrum of the NO-Ar complex, core electron binding energies and the emission spectroscopy of BODIPY in water.

  18. Characteristics of BDE dependent on 10B concentration for accelerator-based BNCT using near-threshold 7Li(p,n)7Be direct neutrons.

    PubMed

    Tanaka, K; Kobayashi, T; Bengua, G; Nakagawa, Y; Endo, S; Hoshi, M

    2004-11-01

    The characteristics boron-dose enhancer (BDE) was evaluated as to the dependence on the (10)B concentration for BNCT using near-threshold (7)Li(p,n)(7)Be direct neutrons. The treatable protocol depth (TPD) was utilized as an evaluation index. MCNP-4B calculations were performed for near-threshold (7)Li(p,n)(7)Be at a proton energy of 1.900MeV and for a polyethylene BDE. Consequently, the TPD was increased by increasing T/N ratio, i.e., the ratio of the (10)B concentration in the tumor ((10)B(Tumor)) to that in the normal tissue ((10)B(Normal)), and by increasing (10)B(Tumor) and (10)B(Normal) for constant T/N ratio. It has been found that the BDE becomes unnecessary from the viewpoint of increasing the TPD, when (10)B(Tumor) is over a certain level.

  19. The rovibrational Hamiltonian for ammonia-like molecules.

    PubMed

    Makarewicz, Jan; Skalozub, Alexander

    2002-03-01

    A new exact quantum mechanical rovibrational Hamiltonian operator for ammonia-like molecules is derived. The Hamiltonian is constructed in a molecular system of axes, such that its z' axis makes a trisection of the pyramidal angle formed by three bond vectors with the vertex on the central atom. The introduced set of the internal rovibrational coordinates is adapted to facilitate a convenient description of the inversion motion. These internal coordinates and the molecular axis system have a remarkable property, namely, the internal vibrational angular momentum of the molecule equals zero. This property significantly reduces the Coriolis coupling and simplifies the form of the Hamiltonian. The correctness of this Hamiltonian is proved by a numerical procedure. The orthogonal Radau vectors allowing us to define a similar molecular axis system and the internal coordinates are considered. The Hamiltonian for the Radau parameterization takes a form simple enough to carry out effectively variational calculations of the molecular rovibrational states. Under the appropriate choice of the variational basis functions, the Hamiltonian matrix elements are fully factorizable and do not have any singularities. A convenient method of symmetrization of the basis functions is proposed.

  20. Near threshold two meson production with the pd→3Heπ+π- and pd→3HeK+K- reactions

    NASA Astrophysics Data System (ADS)

    Bellemann, F.; Berg, A.; Bisplinghoff, J.; Bohlscheid, G.; Ernst, J.; Henrich, C.; Hinterberger, F.; Ibald, R.; Jahn, R.; Jarczyk, L.; Joosten, R.; Kozela, A.; Machner, H.; Magiera, A.; Maschuw, R.; Mayer-Kuckuk, T.; Mertler, G.; Munkel, J.; von Neumann-Cosel, P.; Rosendaal, D.; von Rossen, P.; Schnitker, H.; Scho, K.; Smyrski, J.; Strzalkowski, A.; Tölle, R.; Wilkin, C.

    2000-06-01

    Near threshold two meson production via the reactions pd→3Heπ+π- and pd→3HeK+K- was measured kinematically complete with the MOMO experiment at COSY. The obtained two pion invariant mass spectra and angular distributions depict a remarkable deviation from phase space. The two kaon data are consistent with phase space topped by a clear signal of the φ meson.

  1. Unravelling the dynamical origin of below- and near-threshold harmonic generation of H2+ in an intense NIR laser field

    DOE PAGES

    Heslar, John; Chu, Shih-I.

    2016-11-24

    Recently, the study of near- and below- threshold regime harmonics as a potential source of intense coherent vacuum-ultraviolet radiation has received considerable attention. However, the dynamical origin of these lower harmonics, particularly for the molecular systems, is less understood and largely unexplored. Here we perform the first fully ab initio and high precision 3D quantum study of the below- and near-threshold harmonic generation of H2+ molecules in an intense 800-nm near-infrared (NIR) laser field. Furthermore, combining with a synchrosqueezing transform of the quantum time-frequency spectrum and an extended semiclassical analysis, we explore in-depth the roles of various quantum trajectories, includingmore » short- and long trajectories, multiphoton trajectories, resonance-enhanced trajectories, and multiple rescattering trajectories of the below- and near- threshold harmonic generation processes. Our results shed new light on the dynamical origin of the below- and near-threshold harmonic generation and various quantum trajectories for diatomic molecules for the first time.« less

  2. Irradiation characteristics of BNCT using near-threshold 7Li(p, n)7Be direct neutrons: application to intra-operative BNCT for malignant brain tumours.

    PubMed

    Tanaka, Kenichi; Kobayashi, Tooru; Sakurai, Yoshinori; Nakagawa, Yoshinobu; Ishikawa, Masayori; Hoshi, Masaharu

    2002-08-21

    A calculation method for the dosage of neutrons by near-threshold 7Li(p, n)7Be and gamma rays by 7Li(p, p'gamma)7Li was validated through experiments with variable distance between the Li target and the phantom, focusing on large angular dependence. The production of neutrons and gamma rays in the Li target was calculated by Lee's method and their transport in the phantom was calculated using the MCNP-4B code. The dosage in intra-operative boron neutron capture therapy (BNCT) using near-threshold 7Li(p, n)7Be direct neutrons was evaluated using the validated calculation method. The effectiveness of the usage of the direct neutrons was confirmed from the existence of the region satisfying the requirements of the protocol utilized in intra-operative BNCT for brain tumours in Japan. The boron-dose enhancer (BDE) introduced in this paper to increase the contribution of the 10B(n, alpha)7Li dose in the living body was effective. The void utilized to increase the dose in deep regions was also effective with BDE. For the investigation of 1.900 MeV proton beams, for example, it was found that intraoperative BNCT using near-threshold 7Li(p, n)7Be direct neutrons is feasible.

  3. A Monte Carlo dosimetry-based evaluation of the 7Li(p,n)7Be reaction near threshold for accelerator boron neutron capture therapy.

    PubMed

    Lee, C L; Zhou, X L; Kudchadker, R J; Harmon, F; Harker, Y D

    2000-01-01

    Advanced methods of boron neutron capture therapy (BNCT) use an epithermal neutron beam in conjunction with tumor-targeting boron compounds for irradiation of glioblastomas and metastatic melanomas. A common neutron-producing reaction considered for accelerator-based BNCT is 7Li(p,n)7Be, whose cross section increases very rapidly within several tens of keV of the reaction threshold at 1.88 MeV. Operation in the proton energy region near threshold will have an appreciable thick target neutron yield, but the neutrons produced will have relatively low energies that require little moderation to reach the epithermal range desirable for BNCT. Because of its relatively low projected accelerator cost and the portability of the neutron source/target assembly, BNCT based on the near-threshold technique is considered an attractive candidate for widespread hospital use. A systematic Monte Carlo N-Particle (MCNP) investigation of the dosimetric properties of near-threshold neutron beams has been performed. Results of these studies indicate that accelerator proton energies between 1.93 and 1.99 MeV, using 5 cm of H2O moderator followed by thin 6Li and Pb shields, can provide therapeutically useful beams with treatment times less than one hour and accelerator currents less than 5 mA.

  4. Unravelling the dynamical origin of below- and near-threshold harmonic generation of H2+ in an intense NIR laser field

    SciTech Connect

    Heslar, John; Chu, Shih-I.

    2016-11-24

    Recently, the study of near- and below- threshold regime harmonics as a potential source of intense coherent vacuum-ultraviolet radiation has received considerable attention. However, the dynamical origin of these lower harmonics, particularly for the molecular systems, is less understood and largely unexplored. Here we perform the first fully ab initio and high precision 3D quantum study of the below- and near-threshold harmonic generation of H2+ molecules in an intense 800-nm near-infrared (NIR) laser field. Furthermore, combining with a synchrosqueezing transform of the quantum time-frequency spectrum and an extended semiclassical analysis, we explore in-depth the roles of various quantum trajectories, including short- and long trajectories, multiphoton trajectories, resonance-enhanced trajectories, and multiple rescattering trajectories of the below- and near- threshold harmonic generation processes. Our results shed new light on the dynamical origin of the below- and near-threshold harmonic generation and various quantum trajectories for diatomic molecules for the first time.

  5. Unravelling the dynamical origin of below- and near-threshold harmonic generation of H2+ in an intense NIR laser field

    PubMed Central

    Heslar, John; Chu, Shih-I.

    2016-01-01

    Recently, the study of near- and below- threshold regime harmonics as a potential source of intense coherent vacuum-ultraviolet radiation has received considerable attention. However, the dynamical origin of these lower harmonics, particularly for the molecular systems, is less understood and largely unexplored. Here we perform the first fully ab initio and high precision 3D quantum study of the below- and near-threshold harmonic generation of molecules in an intense 800-nm near-infrared (NIR) laser field. Combining with a synchrosqueezing transform of the quantum time-frequency spectrum and an extended semiclassical analysis, we explore in-depth the roles of various quantum trajectories, including short- and long trajectories, multiphoton trajectories, resonance-enhanced trajectories, and multiple rescattering trajectories of the below- and near- threshold harmonic generation processes. Our results shed new light on the dynamical origin of the below- and near-threshold harmonic generation and various quantum trajectories for diatomic molecules for the first time. PMID:27883061

  6. The ro-vibrational `conveyor belt' for all-optical lasing during laser filamentation in Nitrogen

    NASA Astrophysics Data System (ADS)

    Ivanov, Misha; Richter, Maria; Morales, Felipe; Smirnova, Olga

    2016-05-01

    Inducing and controlling lasing in the open air is an intriguing challenge. Recent experiments on laser filamentation in the air have demonstrated generation of population inversion and lasing on the 391 nm line in the nitrogen ion, which corresponds to the transition between its second excited B2Σu+ and the ground X2Σg+ electronic states. Importantly, lasing at this transition appears to be a very general effect, arising during filamentation of virtually any incident radiation, from visible to mid-infrared. We analyze the possible mechanisms that can be responsible for the generation of the population inversion between the B2Σu+ and X2Σg+ states of N2+,focusing on the interplay between tunnel ionization of neutral nitrogen to different electronic states, ultrafast laser driven electronic excitations in the ion, molecular vibrations, laser induced alignment and rotations. We show how the strong laser field creates a ro-vibrational `conveyor belt' carrying the population away from the ground electronic state X2Σg+ and enabling population inversion in B2Σu+ . We show that this mechanism is robust with respect to the incident laser wavelength, and analyze its optimization with respect to the fundamental wavelength and pulse duration.

  7. Near-threshold emission of electrons during grazing scattering of keV Ne atoms from an Al(111) surface

    SciTech Connect

    Matulevich, Y.; Lederer, S.; Winter, H.

    2005-01-15

    The number of electrons emitted during grazing scattering of Ne atoms with kilo-electron-volt energies from an Al(111) surface is recorded in coincidence with the energy loss of scattered projectiles. Irrespective of the total projectile energies used, we observe a pronounced increase of total electron emission yields when the energy for motion normal to the surface exceeds about 25 eV. Based on energy loss spectra and classical computer simulations of projectile trajectories we attribute electron emission under these scattering conditions to a promotion mechanism in binary collisions between Ne and Al target atoms resulting in single and double excitations of projectiles.

  8. Tests of MULTIMODE calculations of rovibrational energies of CH 4

    NASA Astrophysics Data System (ADS)

    Wu, Jiayan; Huang, Xinchuan; Carter, Stuart; Bowman, Joel M.

    2006-08-01

    We report variational calculations of rovibrational energies of CH 4 using the code MULTIMODE and an ab initio force field of Schwenke and Partridge. The systematic convergence of the energies with respect to the level of mode coupling is presented. Converged vibrational energies calculated using the five-mode representation of the potential for zero total angular momentum are compared with previous, benchmark calculations based on Radau coordinates using this force field for zero total angular momentum and for J = 1. Very good agreement with the previous benchmark calculations is found.

  9. HCO (N,Ka,Kc,J) distributions from near-threshold photolysis of H2CO (J,Ka,Kc)

    NASA Astrophysics Data System (ADS)

    Terentis, Andrew C.; Waugh, Siobhan E.; Metha, Gregory F.; Kable, Scott H.

    1998-02-01

    The dynamics of the reaction H2CO+hν(λ≈330 nm)→H+HCO have been studied following excitation of formaldehyde into the Ã(1A2) state, just above the dissociation threshold of the X˜(1A1) state. Formaldehyde was excited via specific J, Ka, Kc rotational states and the ensuing rotational distribution of HCO measured by fully resolving N, Ka, Kc, and J=N±S of the fragment. When only the N and Ka quantum numbers of both formaldehyde and the formyl radical are considered, the distributions are generally modeled well by phase space theory (PST). Within ≈10 cm-1 of the threshold, however, the PST predictions consistently exceed the experimental populations. This was accounted for by the inclusion of a centrifugal barrier in the PST model. The attractive part of the effective centrifugal potential was modeled by a dipole-induced dipole plus dispersion interaction. The barrier is weak and long range (>5 Å). Resolution of Kc in the reaction, in both parent and product, gave large deviations from the PST model. The HCO population distributions separate according to whether Kc was the upper- or lower-energy state. Additionally, the upper/lower preference was sensitive to the choice of Kc in the parent. Insufficient data are currently available to quantify this observation. The product state distribution was also found to be independent of the spin-rotation state of HCO.

  10. Combined analysis of near-threshold production of ω and φ mesons in nucleon-nucleon collisions within an effective meson-nucleon model

    NASA Astrophysics Data System (ADS)

    Kaptari, L. P.; Kämpfer, B.

    2005-02-01

    Vector meson ( V = ω,φ) production in near-threshold elementary nucleon-nucleon collisions pp↦ppV, pn↦pnV and pn↦dV is studied within an effective meson-nucleon theory. It is shown that a set of effective parameters can be established to describe fairly well the available experimental data of angular distributions and the energy dependence of the total cross-sections without explicit implementation of the Okubo-Zweig-Iizuka rule violation. Isospin effects are considered in detail and compared with experimental data whenever available.

  11. Quantum dynamical calculation of bound rovibrational states of HO2 up to largest possible total angular momentum, J ≤ 130.

    PubMed

    Petty, Corey; Chen, Wenwu; Poirier, Bill

    2013-08-15

    In a previous article [J. Theor. Comput. Chem. 2010, 9, 435], all rovibrational bound states of HO2 were systematically computed, for all total angular momentum values J = 0-10. In this article, the high-J rovibrational states are computed for every multiple-of-ten J value up to J = 130, which is the point where the centrifugal barrier obliterates the potential well, and bound states no longer exist. The results are used to assess the importance of Coriolis coupling in this floppy system and to evaluate two different J-shifting schemes. Though not effective for multiply vibrationally excited bound states, vibrational-state-dependent J-shifting obtains modestly accurate predictions for the lowest-lying energies [J. Phys. Chem. A 2006, 110, 3246]. However, much better performance is obtained-especially for large J values, and despite substantial Coriolis coupling-using a second, rotational-state-dependent J-shifting scheme [J. Chem. Phys. 1998, 108, 5216], for which the rotational constants themselves depend on J and K. The latter formalism also yields important dynamical insight into the structure of the strongly Coriolis-coupled eigenstate wave functions. The calculations were performed using ScalIT, a suite of codes enabling quantum dynamics calculations on massively parallel computing architectures.

  12. Quantum dynamics of rovibrational transitions in H2-H2 collisions: internal energy and rotational angular momentum conservation effects.

    PubMed

    Fonseca dos Santos, S; Balakrishnan, N; Lepp, S; Quéméner, G; Forrey, R C; Hinde, R J; Stancil, P C

    2011-06-07

    We present a full dimensional quantum mechanical treatment of collisions between two H(2) molecules over a wide range of energies. Elastic and state-to-state inelastic cross sections for ortho-H(2) + para-H(2) and ortho-H(2) + ortho-H(2) collisions have been computed for different initial rovibrational levels of the molecules. For rovibrationally excited molecules, it has been found that state-to-state transitions are highly specific. Inelastic collisions that conserve the total rotational angular momentum of the diatoms and that involve small changes in the internal energy are found to be highly efficient. The effectiveness of these quasiresonant processes increases with decreasing collision energy and they become highly state-selective at ultracold temperatures. They are found to be more dominant for rotational energy exchange than for vibrational transitions. For non-reactive collisions between ortho- and para-H(2) molecules for which rotational energy exchange is forbidden, the quasiresonant mechanism involves a purely vibrational energy transfer albeit with less efficiency. When inelastic collisions are dominated by a quasiresonant transition calculations using a reduced basis set involving only the quasiresonant channels yield nearly identical results as the full basis set calculation leading to dramatic savings in computational cost.

  13. Precision Measurement of the Rovibrational Energy-Level Structure of ^{4}He^{+}_{2}

    NASA Astrophysics Data System (ADS)

    Semeria, Luca; Jansen, Paul; Agner, Josef A.; Schmutz, Hansjürg; Merkt, Frederic

    2017-06-01

    He_{2}^{+} is a three-electron system for which highly accurate ab initio calculations are possible. The latest calculations of the rovibrational energies of He_{2}^{+} by Tung et al. have a reported accuracy of 120 MHz, although they do not include relativistic and quantum electrodynamics (QED) effects. We determined the rovibrational structure of ^{4}He^{+}_{2} from measurements of the Rydberg spectrum of metastable a ^3Σ_u^+ He_{2} (He^{*}_{2} hereafter) and Rydberg-series extrapolation using multichannel quantum-defect-theory. He^{*}_{2} molecules are produced in supersonic beams with velocities tunable down to about 100 m/s by combining a cryogenic supersonic-beam source with a multistage Zeeman decelerator. They are then excited to high-np Rydberg states by single-photon excitation. In the experiments, we use a pulsed uv laser system, with a near Fourier-transform-limited bandwidth of 150 MHz. The Zeeman deceleration reduces the systematic uncertainty arising from a possible Doppler shift and greatly simplifies the spectral assignment because of its spin-rotational state selectivity. Results will be presented on the rotational structure of the lowest three vibrational levels of He^{+}_{2}. The unprecedented accuracy that we have obtained for the v^{+}=0 rotational intervals of He_{2}^{+} enables the quantification of the relativistic and QED corrections by comparison with the results of Tung et al.^a W.-C. Tung, M. Pavanello and L. Adamowicz, J. Chem. Phys., 136, 104309, 2012. C. Jungen, Elements of Quantum Defect Theory, in : Handbook of High-resolution Spectroscopy, 2001. D. Sprecher, J. Liu, T. Krähenmann, M. Schäfer, and F. Merkt, J. Chem. Phys., 140, 064304, 2014. A. W. Wiederkehr, S. D. Hogan, M. Andrist, H. Schmutz, B. Lambillotte, J. A. Agner, and F. Merkt., J. Chem. Phys., 135, 214202, 2011. M. Motsch, P. Jansen, J. A. Agner, H. Schmutz, and F. Merkt, Phys. Rev. A, 89, 043420, 2014. P. Jansen, L. Semeria, L. E. Hofer, S. Scheidegger, J. A. Agner

  14. HIGH PRECISION ROVIBRATIONAL SPECTROSCOPY OF OH{sup +}

    SciTech Connect

    Markus, Charles R.; Hodges, James N.; Perry, Adam J.; Kocheril, G. Stephen; McCall, Benjamin J.; Müller, Holger S. P.

    2016-02-01

    The molecular ion OH{sup +} has long been known to be an important component of the interstellar medium. Its relative abundance can be used to indirectly measure cosmic ray ionization rates of hydrogen, and it is the first intermediate in the interstellar formation of water. To date, only a limited number of pure rotational transitions have been observed in the laboratory making it necessary to indirectly calculate rotational levels from high-precision rovibrational spectroscopy. We have remeasured 30 transitions in the fundamental band with MHz-level precision, in order to enable the prediction of a THz spectrum of OH{sup +}. The ions were produced in a water cooled discharge of O{sub 2}, H{sub 2}, and He, and the rovibrational transitions were measured with the technique Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy. These values have been included in a global fit of field free data to a {sup 3}Σ{sup −} linear molecule effective Hamiltonian to determine improved spectroscopic parameters which were used to predict the pure rotational transition frequencies.

  15. ROVIBRATIONALLY RESOLVED PHOTODISSOCIATION OF HeH{sup +}

    SciTech Connect

    Miyake, S.; Gay, C. D.; Stancil, P. C. E-mail: stancil@physast.uga.edu

    2011-07-01

    Accurate photodissociation cross sections have been obtained for the A{sup 1}{Sigma}{sup +} <- X{sup 1}{Sigma}{sup +} electronic transition of HeH{sup +} using ab initio potential curves and dipole transition moments. Partial cross sections have been evaluated for all rotational transitions from the vibrational levels v'' = 0-11 and over the entire accessible wavelength range {lambda}{lambda}100-1129. Assuming a Boltzmann distribution of the rovibrational levels of the X{sup 1}{Sigma}{sup +} state, photodissociation cross sections are presented for temperatures between 500 and 12,000 K. A similar set of calculations was performed for the pure rovibrational photodissociation in the X{sup 1}{Sigma}{sup +} electronic ground state, but covering photon wavelengths into the far-infrared. Applications of the cross sections to the destruction of HeH{sup +} in the early universe and in UV-irradiated environments such as primordial halos and protoplanetary disks are briefly discussed.

  16. Two-Nucleon Processes in Near-Threshold (polarized Proton, Negative Pion) Reactions in the Carbon and Calcium Regions.

    NASA Astrophysics Data System (ADS)

    Throwe, Thomas Gerald

    With the increasing theoretical interest in two -nucleon models (TNM) of pion production, a set of experimental measurements were proposed to show the dominance of two -nucleon processes over other processes in pion production and to show that, in spite of detailed theoretical complexities of TNM's, simple two-nucleon signatures exist. By choosing nuclear systems in which the nuclear structure restricts the target neutrons which might contribute to selected transitions, we are able to make simple predictions regarding cross section and analyzing power behavior for ((')p,(pi)(')) reactions induced on carbon isotopes. The measurements confirm the predictions of a j-dependent signature of the sign of the vector analyzing power for transitions involving target neutrons from j = l + 1/2 and j = l - 1/2 shell model orbitals, and of a simple scaling of the ground-state cross section with neutron excess in the target carbon isotope. In the course of the measurements, an unexpected and strong concentration of (p,(pi)('-)) reaction strength on a variety of target nuclei was discovered. This concentrated (p,(pi)('-)) reaction strength is consistently explained in terms of a two-nucleon mechanism, giving rise to a striking preference for the excitation of high-spin two particle -one hole states in the (p,(pi)('-)) reaction, which is much less pronounced in (p,(pi)('+)). These results suggest significant spectroscopic applications of the (p,(pi)) reaction. All of the measurements presented provide evidence for the dominance of two-nucleon processes in pion production, and also confirm our original hypothesis that the simple aspects of pion production in nuclei may be more clearly manifested in (p,(pi)('-)) than in (p,(pi)('+)) reactions.

  17. Gas Phase Rovibrational Spectroscopy of Dmso, Part II: Towards the Terahertz Observation of 4-FOLD Clusters

    NASA Astrophysics Data System (ADS)

    Cuisset, Arnaud; Martin-Drumel, Marie-Aline; Hindle, Francis; Mouret, Gael; Sadovskii, Dmitrii A.

    2013-06-01

    Benefiting of the exceptional properties of the AILES synchrotron beamline, the gas phase Far-IR spectrum of DMSO has been recorded and resolved. The rovibrational analysis allowed to discover a new rotational behaviour for a polyatomic molecule: the gyroscopic destabilization. In order to explain this phenomenon, we looked for four-fold energy clusters in the high resolution ground state THz spectrum of DMSO recorded with a sub-THz spectrometer based on a frequency multiplication chain. Pure rotational lines in the 5 lowest vibrationnally excited levels have been recorded below 700 GHz. With near 1000 rotational transitions assigned, high quantum numbers have been reached allowing to discover sequence of four-fold clusters in the out of plane bending mode of DMSO and to study the vibrational dependence of an unusual rotational dynamics. J. B. Brubach et al., AIP Conf. Proc., 1214, (81), 2010. A. Cuisset, L. Nanobashvili, I. Smirnova, R. Bocquet, F. Hindle, G. Mouret, O. Pirali, P. Roy, D. Sadovskii,Chem. Phys. Lett., 492,(30),2010 A. Cuisset, O. Pirali, D. Sadovskii,Phys. Rev. Lett., 109,(094101), 2012. G. Mouret, M. Guinet, A. Cuisset, L. Croizet, S. Eliet, R. Bocquet, F. Hindle, IEEE Sensors Journal, 13, 1, 2013.

  18. Higher energy states in the CO dimer: millimeter-wave spectra and rovibrational calculations.

    PubMed

    Surin, Leonid A; Fourzikov, Dmitri N; Giesen, Thomas F; Schlemmer, Stephan; Winnewisser, Gisbert; Panfilov, Victor A; Dumesh, Boris S; Vissers, Gé W M; van der Avoird, Ad

    2007-12-13

    New extensive millimeter-wave measurements of the 12C16O dimer have been made, and more than 300 new spectral transitions have been observed in the frequency range 81-135 GHz. A joint analysis of these and previous millimeter-wave data yielded the precise location of 33 new energy levels of A+ symmetry and 20 levels of A- symmetry. These energy levels are located at 8-18 cm(-1) above the zero-point level. Some of them belong to already known stacks, and others make up 9 new stacks of the dimer. Newly determined stacks have K=0, 1, and, for the first time, 2, where K is the projection of the total angular momentum on the intermolecular axis. The energy levels from accompanying rovibrational calculations with the use of a recently developed hybrid CCSD(T)/DFT-SAPT potential are in very good agreement with experiment. Analysis of the calculated wave functions revealed that two new stacks of A+ symmetry with K=2 correspond to overall rotation of the dimer while the other newly observed stacks belong to the geared bend overtone modes. The ground vibrational states of the two "isomers" found are more or less localized at the two minima in the potential surface, whereas all the geared bend excited states show a considerable amount of delocalization.

  19. High-Level, First-Principles, Full-Dimensional Quantum Calculation of the Ro-vibrational Spectrum of the Simplest Criegee Intermediate (CH2OO).

    PubMed

    Li, Jun; Carter, Stuart; Bowman, Joel M; Dawes, Richard; Xie, Daiqian; Guo, Hua

    2014-07-03

    The ro-vibrational spectrum of the simplest Criegee intermediate (CH2OO) has been determined quantum mechanically based on nine-dimensional potential energy and dipole surfaces for its ground electronic state. The potential energy surface is fitted to more than 50 000 high-level ab initio points with a root-mean-square error of 25 cm(-1), using a recently proposed permutation invariant polynomial neural network method. The calculated rotational constants, vibrational frequencies, and spectral intensities of CH2OO are in excellent agreement with experiment. The potential energy surface provides a valuable platform for studying highly excited vibrational and unimolecular reaction dynamics of this important molecule.

  20. Quantum Electrodynamics Effects in Rovibrational Spectra of Molecular Hydrogen.

    PubMed

    Komasa, Jacek; Piszczatowski, Konrad; Łach, Grzegorz; Przybytek, Michał; Jeziorski, Bogumił; Pachucki, Krzysztof

    2011-10-11

    The dissociation energies from all rovibrational levels of H2 and D2 in the ground electronic state are calculated with high accuracy by including relativistic and quantum electrodynamics (QED) effects in the nonadiabatic treatment of the nuclear motion. For D2, the obtained energies have theoretical uncertainties of 0.001 cm(-1). For H2, similar uncertainties are for the lowest levels, while for the higher ones the uncertainty increases to 0.005 cm(-1). Very good agreement with recent high-resolution measurements of the rotational v = 0 levels of H2, including states with large angular momentum J, is achieved. This agreement would not have been possible without accurate evaluation of the relativistic and QED contributions and may be viewed as the first observation of the QED effects, mainly the electron self-energy, in a molecular spectrum. For several electric quadrupole transitions, we still observe certain disagreement with experimental results, which remains to be explained.

  1. Observation of a Near-Threshold Enhancement in the ωϕ Mass Spectrum from the Doubly OZI-Suppressed Decay J/ψ→γωϕ

    NASA Astrophysics Data System (ADS)

    Ablikim, M.; Bai, J. Z.; Ban, Y.; Bian, J. G.; Cai, X.; Chen, H. F.; Chen, H. S.; Chen, H. X.; Chen, J. C.; Chen, Jin; Chen, Y. B.; Chi, S. P.; Chu, Y. P.; Cui, X. Z.; Dai, Y. S.; Diao, L. Y.; Deng, Z. Y.; Dong, Q. F.; Du, S. X.; Fang, J.; Fang, S. S.; Fu, C. D.; Gao, C. S.; Gao, Y. N.; Gu, S. D.; Gu, Y. T.; Guo, Y. N.; Guo, Y. Q.; Guo, Z. J.; Harris, F. A.; He, K. L.; He, M.; Heng, Y. K.; Hu, H. M.; Hu, T.; Huang, G. S.; Huang, X. T.; Ji, X. B.; Jiang, X. S.; Jiang, X. Y.; Jiao, J. B.; Jin, D. P.; Jin, S.; Jin, Yi; Lai, Y. F.; Li, G.; Li, H. B.; Li, H. H.; Li, J.; Li, R. Y.; Li, S. M.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, Y. L.; Liang, Y. F.; Liao, H. B.; Liu, B. J.; Liu, C. X.; Liu, F.; Liu, Fang; Liu, H. H.; Liu, H. M.; Liu, J.; Liu, J. B.; Liu, J. P.; Liu, Q.; Liu, R. G.; Liu, Z. A.; Lou, Y. C.; Lu, F.; Lu, G. R.; Lu, J. G.; Luo, C. L.; Ma, F. C.; Ma, H. L.; Ma, L. L.; Ma, Q. M.; Ma, X. B.; Mao, Z. P.; Mo, X. H.; Nie, J.; Olsen, S. L.; Peng, H. P.; Ping, R. G.; Qi, N. D.; Qin, H.; Qiu, J. F.; Ren, Z. Y.; Rong, G.; Shan, L. Y.; Shang, L.; Shen, C. P.; Shen, D. L.; Shen, X. Y.; Sheng, H. Y.; Sun, H. S.; Sun, J. F.; Sun, S. S.; Sun, Y. Z.; Sun, Z. J.; Tan, Z. Q.; Tang, X.; Tong, G. L.; Varner, G. S.; Wang, D. Y.; Wang, L.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, W. F.; Wang, Y. F.; Wang, Z.; Wang, Z. Y.; Wang, Zhe; Wang, Zheng; Wei, C. L.; Wei, D. H.; Wu, N.; Xia, X. M.; Xie, X. X.; Xu, G. F.; Xu, X. P.; Xu, Y.; Yan, M. L.; Yang, H. X.; Yang, Y. X.; Ye, M. H.; Ye, Y. X.; Yi, Z. Y.; Yu, G. W.; Yuan, C. Z.; Yuan, J. M.; Yuan, Y.; Zang, S. L.; Zeng, Y.; Zeng, Yu; Zhang, B. X.; Zhang, B. Y.; Zhang, C. C.; Zhang, D. H.; Zhang, H. Q.; Zhang, H. Y.; Zhang, J. W.; Zhang, J. Y.; Zhang, S. H.; Zhang, X. M.; Zhang, X. Y.; Zhang, Yiyun; Zhang, Z. P.; Zhao, D. X.; Zhao, J. W.; Zhao, M. G.; Zhao, P. P.; Zhao, W. R.; Zhao, Z. G.; Zheng, H. Q.; Zheng, J. P.; Zheng, Z. P.; Zhou, L.; Zhou, N. F.; Zhu, K. J.; Zhu, Q. M.; Zhu, Y. C.; Zhu, Y. S.; Zhu, Yingchun; Zhu, Z. A.; Zhuang, B. A.; Zhuang, X. A.; Zou, B. S.

    2006-04-01

    An enhancement near threshold is observed in the ωϕ invariant mass spectrum from the doubly Okubo-Zweig-Iizuka suppressed decays of J/ψ→γωϕ, based on a sample of 5.8×107 J/ψ events collected with the BESII detector. A partial wave analysis shows that this enhancement favors JP=0+, and its mass and width are M=1812-26+19(stat)±18(syst)MeV/c2 and Γ=105±20(stat)±28(syst)MeV/c2. The product branching fraction is determined to be B(J/ψ→γX)B(X→ωϕ)=[2.61±0.27(stat)±0.65(syst)]×10-4.

  2. Effects of dendrite cell size and particle distribution on the near-threshold fatigue crack growth behavior of cast Al-SiCp composites

    SciTech Connect

    Kumai, S.; Hu, J.; Higo, Y.; Nunomura, S.

    1996-06-01

    Fatigue crack growth tests and crack closure measurements were performed for A356 cast aluminium alloys reinforced by 10 or 20% SiC particles and their matrix A356 alloys with systematically controlled dendrite cell size and particle distribution. The cell size dependence of the fatigue crack growth behavior in the composite was found to be quite similar to that of the matrix alloy. This suggests that the cell size rather than the particle-crack tip interaction is the most important factor to control the fatigue crack growth of the composites. Near threshold fatigue crack growth properties were improved in the composites with coarser cell size and inhomogeneous particle distribution due to the enhanced roughness induced crack closure effect. These results were compared to those of powder-metallurgically-processed materials.

  3. Rovibrational Satellite Bands of the br Spin-Orbit Transition in br Doped Solid Parahydrogen

    NASA Astrophysics Data System (ADS)

    Anderson, David T.

    2009-06-01

    In the isolated atom the Br spin-orbit (SO) transition is electric-dipole-forbidden because this transition (^2P_{1/2} ← ^2P_{3/2}) does not involve a change in parity. The isolated Br SO transition therefore acquires intensity from magnetic-dipole and electric-quadrupole terms in the atom-field interaction Hamiltonian and this makes this transition inherently weak. Nonetheless, the Br SO transition is observed in Br-atom doped solid parahydrogen (pH_2) crystals prepared at liquid helium temperatures. It will be shown that the intensity of the Br SO transition is greater when isolated in solid pH_2 due to weak intermolecular interactions of the Br atom with the pH_2 matrix. The small increase in the Br SO transition strength results because the Br atom resides in a single substitution site of the hexagonal closed packed pH_2 crystal which lacks a center of inversion. In addition, a vibrational satellite absorption is detected shifted to higher energy by one quantum of H_2 vibration. This vibrational satellite absorption is stronger than the pure SO transition because simultaneous excitation of the Br SO and H_2 vibrational excitation in the pair gives even greater electric-dipole character to the transition. IR spectral evidence for rotational, vibrational, and rovibrational satellite bands of the Br SO transition will be presented. The fact that the rotational and vibrational quantum states of the H_2 molecule are conserved in solid pH_2 accounts for why these satellite absorptions come at well-defined discrete frequencies. The frequencies and lineshapes of these satellite absorptions provide detailed information on the SO state dependent Br-H_2 intermolecular potential.

  4. New near-threshold mesons

    NASA Astrophysics Data System (ADS)

    Cohen, Thomas D.; Gelman, Boris A.; Nussinov, Shmuel

    2004-01-01

    We show that under a number of rather plausible assumptions QCD spectrum may contain a number of mesons which have not been predicted or observed. Such states will have the quantum numbers of two existing mesons and masses very close to the dissociation threshold into the two mesons. Moreover, at least one of the two mesonic constituents itself must be very close to its dissociation threshold. In particular, one might expect the existence of loosely bound systems of D and D∗sJ(2317); similarly, K and f0(980), K¯ and f0(980), K and a0(980) and K¯ and a0(980) can be bound. The mechanism for binding in these cases is the S-wave kaon exchange. The nearness of one of the constituents to its decay threshold into a kaon plus a remainder, implies that the range of the kaon exchange force becomes abnormally long—significantly longer than 1/mK which greatly aids the binding.

  5. Direct Electron Impact Excitation of Rydberg-Valence States of Molecular Nitrogen

    NASA Astrophysics Data System (ADS)

    Malone, C. P.; Johnson, P. V.; Liu, X.; Ajdari, B.; Muleady, S.; Kanik, I.; Khakoo, M. A.

    2012-12-01

    .82eV. This effort is to provide improved cross sections for these RV states, in particular for the b‧ 1Σu+ and c‧4 1Σu+ states, with inclusion of more upper vibrational levels. Future optical emission work should include re-measurements of excitation shape functions of the singlet ungerade states utilizing better spectral resolution than past determinations (e.g., [2,4]) to avoid uncertainties associated with unresolved and/or blended spectral features as well as J-dependent predissociation. Further development of theoretical treatments of N2 excitation is also in need. We will also present analysis of our new low-energy, near-threshold excitation cross sections for the valence states of N2, including a 1Πg (v‧) levels. Acknowledgement: This work was performed at CSUF and JPL, Caltech, under contract with NASA. We gratefully acknowledge financial support through NASA's OPR and PATM programs and NSF-PHY-RUI-0096808 & -0965793 and NSF-AGS-0938223. References: [1] Ajello, J. M., M. H. Stevens, I. Stewart, et al. (2007), GRL, 34, L24204 [2] Ajello, J. M., G. K. James, and B. O. Franklin (1989), PRA, 40, 3524-56 [3] Heays, A. N., B. R. Lewis, S. T. Gibson, et al. (2012), PRA, 85, 012705 [4] James, G. K., J. M. Ajello, B. Franklin, and D. E. Shemansky (1990), JPB, 23, 2055-81 [5] Khakoo, M. A., C. P. Malone, P. V. Johnson, et al. (2008), PRA, 77, 012704 [6] Malone, C. P., P. V. Johnson, X. Liu, et al. (2012), PRA, 85, 062704

  6. Objective detection of auditory evoked potentials. Comparison of several statistical tests in the frequency domain on the basis of near-threshold ABR data.

    PubMed

    Stürzebecher, E; Cebulla, M

    1997-01-01

    A fully objective electric response audiometry (ERA) requires an objective response detection by an appropriate statistical test. The Rayleigh test, Watson's U2 test, Kuiper's test and Hodges-Ajne's test check the phase angle distribution of a Fourier harmonics. The modified Rayleigh test uses, in addition to the phase angles, the amplitude information in the form of the ranks of the spectral amplitudes, whereas magnitude-squared coherence (MSC) uses the spectral amplitudes themselves. The signal detection performance of these six tests was judged on the basis of a sample of near-threshold click-evoked ABR. MSC was found to be the best suited test out of the six tests investigated, but the performance differences to the modified Rayleigh test (and even to the unmodified Rayleigh test), and to Watson's test as well were only slight. Hodges-Ajne's test and Kuiper's test have the lowest sensitivity and the mean time required for response detection is longest for Hodges-Ajne's test.

  7. Near-threshold equal-loudness contours for harbor seals (Phoca vitulina) derived from reaction times during underwater audiometry: a preliminary study.

    PubMed

    Kastelein, Ronald A; Wensveen, Paul J; Terhune, John M; de Jong, Christ A F

    2011-01-01

    Equal-loudness functions describe relationships between the frequencies of sounds and their perceived loudness. This pilot study investigated the possibility of deriving equal-loudness contours based on the assumption that sounds of equal perceived loudness elicit equal reaction times (RTs). During a psychoacoustic underwater hearing study, the responses of two young female harbor seals to tonal signals between 0.125 and 100 kHz were filmed. Frame-by-frame analysis was used to quantify RT (the time between the onset of the sound stimulus and the onset of movement of the seal away from the listening station). Near-threshold equal-latency contours, as surrogates for equal-loudness contours, were estimated from RT-level functions fitted to mean RT data. The closer the received sound pressure level was to the 50% detection hearing threshold, the more slowly the animals reacted to the signal (RT range: 188-982 ms). Equal-latency contours were calculated relative to the RTs shown by each seal at sound levels of 0, 10, and 20 dB above the detection threshold at 1 kHz. Fifty percent detection thresholds are obtained with well-trained subjects actively listening for faint familiar sounds. When calculating audibility ranges of sounds for harbor seals in nature, it may be appropriate to consider levels 20 dB above this threshold.

  8. The Role of a 1 (1260) in π- p → a 1 -(1260)p and π- p → π-ρ0 p Reactions Near Threshold

    NASA Astrophysics Data System (ADS)

    Cheng, Chen; Xie, Ju-Jun; Cao, Xu

    2016-12-01

    We report on a theoretical study of the π- p → a1 -(1260)p and π-p → π- ρ0p reactions near threshold within an effective Lagrangian approach. The production process is described by t-channel ρ0 meson exchange. For the π-p → π-ρ0p reaction, the final π-p0 results from the decay of the a1(1260) resonance, which is assumed as a dynamically generated state from the K*K¯ and ρπ coupled channel interactions. We calculate the total cross section of the π-p → a1 -(1260)p reaction. It is shown that, with the coupling constant of the a1(1260) to ρπ channel obtained from the chiral unitary theory and a cut off parameter Λρ ˜ 1.5 GeV in the form factors, the experimental measurement can be reproduced. Furthermore, the total and differential cross sections of π-p → a1 -(1260)p → π-ρ0p reaction are evaluated, and it is expected that our model calculations can be tested by future experiments. These reactions are important for the study of the a1(1260) resonance and would provide further constraints on the properties of the a1(1260) state. Supported by the National Natural Science Foundation of China under Grant Nos. 11475227 and 11475015, and the Youth Innovation Promotion Association CAS under Grant No. 2016367

  9. Approach to chaos in ultracold atomic and molecular physics: Statistics of near-threshold bound states for Li+CaH and Li+CaF

    NASA Astrophysics Data System (ADS)

    Frye, Matthew D.; Morita, Masato; Vaillant, Christophe L.; Green, Dermot G.; Hutson, Jeremy M.

    2016-05-01

    We calculate near-threshold bound states and Feshbach resonance positions for atom-rigid-rotor models of the highly anisotropic systems Li+CaH and Li+CaF. We perform statistical analysis on the resonance positions to compare with the predictions of random matrix theory. For Li+CaH with total angular momentum J =0 we find fully chaotic behavior in both the nearest-neighbor spacing distribution and the level number variance. However, for J >0 we find different behavior due to the presence of a nearly conserved quantum number. Li+CaF (J =0 ) also shows apparently reduced levels of chaotic behavior despite its stronger effective coupling. This may indicate the development of another good quantum number relating to a bending motion of the complex. However, continuously varying the rotational constant over a wide range shows unexpected structure in the degree of chaotic behavior, including a dramatic reduction around the rotational constant of CaF. This demonstrates the complexity of the relationship between coupling and chaotic behavior.

  10. Space-time resolved simulation of femtosecond nonlinear light-matter interactions using a holistic quantum atomic model: application to near-threshold harmonics.

    PubMed

    Kolesik, M; Wright, E M; Andreasen, J; Brown, J M; Carlson, D R; Jones, R J

    2012-07-02

    We introduce a new computational approach for femtosecond pulse propagation in the transparency region of gases that permits full resolution in three space dimensions plus time while fully incorporating quantum coherent effects such as high-harmonic generation and strong-field ionization in a holistic fashion. This is achieved by utilizing a one-dimensional model atom with a delta-function potential which allows for a closed-form solution for the nonlinear optical response due to ground-state to continuum transitions. It side-steps evaluation of the wave function, and offers more than one hundred-fold reduction in computation time in comparison to direct solution of the atomic Schrödinger equation. To illustrate the capability of our new computational approach, we apply it to the example of near-threshold harmonic generation in Xenon, and we also present a qualitative comparison between our model and results from an in-house experiment on extreme ultraviolet generation in a femtosecond enhancement cavity.

  11. Near-Threshold Total Dissociation Electron Impact Cross Sections for C2F6, C3F8, and CHF3

    NASA Astrophysics Data System (ADS)

    Flaherty, David; Kasper, Michael; Graves, David; Winters, Harold

    2004-09-01

    Absolute total dissociation electron impact cross sections, σ _TD, are reported near threshold (8-30eV) for C_2F_6, C_3F_8, and CHF3 using the technique described by Winters and Inokuti [1]. Total neutral dissociation cross sections, σ _ND, are obtained by subtraction using total ionization cross sections, e.g. [2]. σ _ND for C_2F6 and C_3F8 are compared with values inferred from swarm data and to reported partial dissociation cross sections for production of CF3 and C_2F5 over the range of electron energies measured [3,4]. Work supported in part by the NSF/SRC ERC for Environmentally Benign Semiconductor Manufacturing. [1] H. Winters and M. Inokuti, Phys. Rev. A 25, 1420 (1982). [2] L. Christophorou and J. Olthoff, J. Phys. Chem. Ref. Data 28, 131, (1999) [3] S. Motlagh and J. Moore, J. Chem. Phys., Vol. 109 (2), 432, (1998) [4] Hayashi and Niwa, Gaseous Dielectrics V, Pergamon, New York, p. 27, (1987).

  12. Rovibrational bound states of SO2 isotopologues. I: Total angular momentum J = 0-10

    NASA Astrophysics Data System (ADS)

    Kumar, Praveen; Ellis, Joseph; Poirier, Bill

    2015-04-01

    Isotopic variation of the rovibrational bound states of SO2 for the four stable sulfur isotopes 32-34,36S is investigated in comprehensive detail. In a two-part series, we compute the low-lying energy levels for all values of total angular momentum in the range J = 0-20. All rovibrational levels are computed, to an extremely high level of numerical convergence. The calculations have been carried out using the ScalIT suite of parallel codes. The present study (Paper I) examines the J = 0-10 rovibrational levels, providing unambiguous symmetry and rovibrational label assignments for each computed state. The calculated vibrational energy levels exhibit very good agreement with previously reported experimental and theoretical data. Rovibrational energy levels, calculated without any Coriolis approximations, are reported here for the first time. Among other potential ramifications, this data will facilitate understanding of the origin of mass-independent fractionation of sulfur isotopes in the Archean rock record-of great relevance for understanding the "oxygen revolution".

  13. Rovibrational Interactions in the Ground and Two Lowest Excited Vibrational States of Methoxy Isocyanate

    NASA Astrophysics Data System (ADS)

    Pienkina, A.; Margulès, L.; Motiyenko, R. A.; Guillemin, J.-C.

    2017-06-01

    Recent detection of methyl isocyanate (CH_3NCO) in the Orion, towards Sgr B2(N) and on the surface of the comet 67P/Churyumov-Gerasimenko motivated us to study another isocyanate, methoxy isocyanate (CH_3ONCO) as a possible candidate molecule for searches in the interstellar clouds. Neither identification or laboratory rotational spectra of CH_3ONCO has been reported up to now. Methoxy isocyanate was synthesized by the flash vacuum pyrolysis of N-Methoxycarbonyl-O-methyl-hydroxylamine (MeOC(O)NHOMe) at a temperature of 800 K. Experimental spectrum of CH_3ONCO was recorded in situ in the millimeter-wave range (75-105 GHz and 150-330 GHz) using Lille's fast-scan fully solid-state DDS spectrometer. The recorded spectrum is strongly perturbed due to the interaction between the overall rotation and the skeletal torsion. Perturbations affect even rotational transitions with low K_a levels of the ground vibrational state, appearing in shifting frequency predictions and intensities distortions of the lines. The interactions are significant due to the relatively small vibrational energy difference (≈50 \\wn) between the states and different representations of the C_s symmetry point group for the ground (A'), ν_{18}=1 (A'') and ν_{18}=2 (A') vibrational states, thus leading to a "ladder" of multiple resonances by means of a-, and b-type Coriolis coupling. The global fit analysis of the rotational spectrum of methoxy isocyanate using Coriolis coupling terms in the ground and two lowest vibrational states (ν_{18}=1 and ν_{18}=2) will be presented. J. Cernicharo, N. Marcelino, E. Roueff et al. 2012, ApJ, 759, L43 D. T. Halfen, V. V. Ilyushin, & L. M. Ziurys, 2015, ApJ, 812, L5 F. Goesmann, H. Rosenbauer, J. H. Bredehöft et al. 2015, Science, 349.6247, aab0689 This work was funded by the French ANR under the Contract No. ANR-13-BS05-0008-02 IMOLABS.

  14. Rovibrational energy transfer in the He-C{sub 3} collision: Potential energy surface and bound states

    SciTech Connect

    Denis-Alpizar, Otoniel; Stoecklin, Thierry Halvick, Philippe

    2014-02-28

    We present a four-dimensional potential energy surface (PES) for the collision of C{sub 3} with He. Ab initio calculations were carried out at the coupled-cluster level with single and double excitations and a perturbative treatment of triple excitations, using a quadruple-zeta basis set and mid-bond functions. The global minimum of the potential energy is found to be −26.9 cm{sup −1} and corresponds to an almost T-shaped structure of the van der Waals complex along with a slightly bent configuration of C{sub 3}. This PES is used to determine the rovibrational energy levels of the He-C{sub 3} complex using the rigid monomer approximation (RMA) and the recently developed atom-rigid bender approach at the Close Coupling level (RB-CC). The calculated dissociation energies are −9.56 cm{sup −1} and −9.73 cm{sup −1}, respectively at the RMA and RB-CC levels. This is the first theoretical prediction of the bound levels of the He-C{sub 3} complex with the bending motion.

  15. Angular Correlation Between Kx-Rays and Gamma - in a Spherically-Deformed Nuclei and Measurement of Absolute Pair Production Cross-Sections Near Threshold Energies.

    NASA Astrophysics Data System (ADS)

    Khalil, Ali El Sayed

    1982-03-01

    (i) Measurements of the directional correlations between Kx-rays following internal conversion and (gamma) -rays in ('181)Ta have been made the correlation coefficients are:. A(,22)(K(alpha)(,1) - 133(gamma)) = 0.037 (+OR -) 0.012. A(,44)(K(alpha)(,1) - 133(gamma)) = 0.022 (+OR -) 0.017. A(,22)(K(alpha)(,2) - 133(gamma)) = 0.038 (+OR -) 0.017. A(,44)(K(alpha)(,2) - 133(gamma)) = 0.037 (+OR -) 0.029. The anisotropic correlation measurements in ('181)Ta establish the second known case of this phenomenon. The x-rays follow four internally converted transitions from which 38% of the Kx-rays follow electric-quadrupole internal conversion processes. This anisotropy is caused by the perturbation of the wave functions of the atomic electrons by the static nuclear quadrupole moment which causes a mixture of the two-coupled, two-electron states (VBAR)d'(,3/2), 1s(,1/2), J = 2 > and (VBAR)d'(,5/2), 1s(,1/2), J = 2 > with the unperturbed state (VBAR)1s(,1/2), 1s(,1/2), J = 0 >. The K-shell electrons are then in a quantum state which is an admixture of the three states mentioned above, and K-shell internal conversion results in a d'(,3/2) or d'(,5/2) vacancy in the mixed K-shell state. Accordingly, x-rays form the transition between either 2p(,3/2) or the 2p(,1/2) level, to a d'(,3/2) or d'(,5/2) vacancy, following internal conversion, can result in anisotropic x-ray angular distributions relative to the nuclear symmetry axis. This in turn results in anisotropic directional correlations between Kx-rays and nuclear (gamma)-rays. (ii) Absolute electron-positron pair production cross-sections near threshold energies have been screened. A new technique which is called internal source method is developed. Direct measurements of the cross-section using 2.615 Mev, a mixture of (1.33 + 1.77) Mev, and 1.12 Mev on target materials of Z = 26, 29, 50, 82 and 92 have been obtained. The experimental results agree well with the exact screening calculations for low Z materials; systematic

  16. Ro-vibrational Stark effect on H2 and D2 molecules adsorbed in NaA zeolite

    NASA Astrophysics Data System (ADS)

    Bras, N.

    1999-03-01

    In order to explain the induced infrared bands of H2 and D2 adsorbed in NaA zeolites the Stark effect on the ro-vibrational levels of these molecules is considered for electric fields created by various charge distributions. The shift and intensity of the induced ro-vibration transitions are calculated.

  17. Near-threshold (7)Li(p,n)(7)Be neutrons on the practical conditions using thick Li-target and Gaussian proton energies for BNCT.

    PubMed

    Kobayashi, Tooru; Hayashizaki, Noriyosu; Katabuchi, Tatsuya; Tanaka, Kenichi; Bengua, Gerard; Nakao, Noriaki; Kosako, Kazuaki

    2014-06-01

    The near threshold (7)Li(p,n)(7)Be neutrons generated by incident proton energy having Gaussian distribution with mean energies from 1.85 to 1.95MeV, were studied as a practical neutron source for BNCT wherein an RFQ accelerator and a thick Li-target are used. Gaussian energy distributions with the standard deviation of 0, 10, 20 and 40keV for mean proton energies from 1.85 to 1.95MeV were surveyed in 0.01MeV increments. A thick liquid Li-target whose dimensions were established in our previous experiments (i.e., 1mm-thick with 50mm width and 50mm length) was considered in this study. The suitable incident proton energy and physical dimensions of Pb layer which serves as a gamma absorber and a Polyethylene layer which is used as a BDE were surveyed by means of the concepts of TPD. Dose distribution were calculated by using MCNP5. A proton beam with mean energy of 1.92MeV and a Gaussian energy distribution with a standard deviation of 20keV at a current of 10mA was selected from the viewpoint of irradiation time and practically achievable proton current. The suitable thicknesses of Pb gamma absorber was estimated to be about 3cm. The estimated thickness of the polyethylene BDE was about 24mm for an ideal proton current of 13mA, and was 18mm for a practical proton current of 10mA.

  18. Conflict Resolution as Near-Threshold Decision-Making: A Spiking Neural Circuit Model with Two-Stage Competition for Antisaccadic Task

    PubMed Central

    Wang, Xiao-Jing

    2016-01-01

    Automatic responses enable us to react quickly and effortlessly, but they often need to be inhibited so that an alternative, voluntary action can take place. To investigate the brain mechanism of controlled behavior, we investigated a biologically-based network model of spiking neurons for inhibitory control. In contrast to a simple race between pro- versus anti-response, our model incorporates a sensorimotor remapping module, and an action-selection module endowed with a “Stop” process through tonic inhibition. Both are under the modulation of rule-dependent control. We tested the model by applying it to the well known antisaccade task in which one must suppress the urge to look toward a visual target that suddenly appears, and shift the gaze diametrically away from the target instead. We found that the two-stage competition is crucial for reproducing the complex behavior and neuronal activity observed in the antisaccade task across multiple brain regions. Notably, our model demonstrates two types of errors: fast and slow. Fast errors result from failing to inhibit the quick automatic responses and therefore exhibit very short response times. Slow errors, in contrast, are due to incorrect decisions in the remapping process and exhibit long response times comparable to those of correct antisaccade responses. The model thus reveals a circuit mechanism for the empirically observed slow errors and broad distributions of erroneous response times in antisaccade. Our work suggests that selecting between competing automatic and voluntary actions in behavioral control can be understood in terms of near-threshold decision-making, sharing a common recurrent (attractor) neural circuit mechanism with discrimination in perception. PMID:27551824

  19. Conflict Resolution as Near-Threshold Decision-Making: A Spiking Neural Circuit Model with Two-Stage Competition for Antisaccadic Task.

    PubMed

    Lo, Chung-Chuan; Wang, Xiao-Jing

    2016-08-01

    Automatic responses enable us to react quickly and effortlessly, but they often need to be inhibited so that an alternative, voluntary action can take place. To investigate the brain mechanism of controlled behavior, we investigated a biologically-based network model of spiking neurons for inhibitory control. In contrast to a simple race between pro- versus anti-response, our model incorporates a sensorimotor remapping module, and an action-selection module endowed with a "Stop" process through tonic inhibition. Both are under the modulation of rule-dependent control. We tested the model by applying it to the well known antisaccade task in which one must suppress the urge to look toward a visual target that suddenly appears, and shift the gaze diametrically away from the target instead. We found that the two-stage competition is crucial for reproducing the complex behavior and neuronal activity observed in the antisaccade task across multiple brain regions. Notably, our model demonstrates two types of errors: fast and slow. Fast errors result from failing to inhibit the quick automatic responses and therefore exhibit very short response times. Slow errors, in contrast, are due to incorrect decisions in the remapping process and exhibit long response times comparable to those of correct antisaccade responses. The model thus reveals a circuit mechanism for the empirically observed slow errors and broad distributions of erroneous response times in antisaccade. Our work suggests that selecting between competing automatic and voluntary actions in behavioral control can be understood in terms of near-threshold decision-making, sharing a common recurrent (attractor) neural circuit mechanism with discrimination in perception.

  20. Transient HDO rovibrational satellite peaks in solid parahydrogen: Evidence of hydrogen atoms or vacancies?

    NASA Astrophysics Data System (ADS)

    Wonderly, William R.; Anderson, David T.

    2012-08-01

    In this paper we present FTIR studies of the 193 nm photolysis of fully deuterated formic acid (DCOOD) isolated in solid parahydrogen at 1.9 K, which show evidence of transient HDO rovibrational satellite peaks. The S1 and S2 satellite peaks are readily detected for a-type (101 ← 000) rovibrational transitions of HDO either during or immediately after photolysis. Intensity measurements show the HDO b-type (111 ← 000) rovibrational transitions have satellite peaks as well, but due to the greater linewidth of these absorptions, the satellite peaks cannot be spectroscopically resolved from the monomer transition, and are therefore difficult to detect. These newly identified HDO satellite peaks may result from the HDO photoproduct being formed next to an H atom or a vacancy in the parahydrogen solid. The development of infrared spectroscopy of these satellite peaks can provide a new means to study radiation effects on low-temperature hydrogen solids doped with chemical species.

  1. Ro-vibrational properties of FeCO in the X ˜ 3Σ- and a ˜ 5Σ- electronic states: A computational molecular spectroscopy study

    NASA Astrophysics Data System (ADS)

    Hirano, Tsuneo; Nagashima, Umpei

    2015-08-01

    The present work complements our previous study of the geometry and electronic structure in the ground and low-lying electronic states of FeCO. Here, we report three-dimensional potential energy surfaces (PESs) for the 3Σ- electronic ground state and its high-spin counterpart, the excited state a ˜ 5Σ-, calculated ab initio at the MR-SDCI+Q_DK3/[5ZP ANO-RCC (Fe, C, O)] level of theory. These PESs are employed in 2nd-order-perturbation-theory and DVR3D calculations of the rotation-vibration energies and ro-vibrationally averaged structures. The equilibrium structures determined from the 3D PESs have re (Fe-C) = 1.7247 Å, re (C-O) = 1.1587 Å, and ∠e (Fe-C-O) = 180° for the X ˜ 3Σ- state, and re (Fe-C) = 1.8429 Å, re (C-O) = 1.1522 Å, and ∠e (Fe-C-O) = 180° for the a ˜ 5Σ- state. The ro-vibrationally averaged structures, determined as expectation values over DVR3D wavefunctions, have < r (Fe-C)>0 = 1.7303 Å, < r (C-O)>0 = 1.1631 Å, and < ∠ (Fe-C-O)>0 = 172.6° for the X ˜ 3Σ- state, and < r (Fe-C)>0 = 1.8471 Å, < r (C-O)>0 = 1.1568 Å, and < ∠ (Fe-C-O)>0 = 171.4° for the a ˜ 5Σ- state. The coordinate-covalent Fe-C bond in the X ˜ 3Σ- state, which elongates significantly as the molecule bends, is shown to exhibit normal large amplitude bending motion with strong coupling (manifested by the large value of the relevant third order force constant) between bending and Fe-C stretching modes. The ionic Fe-C bond in the a ˜ 5Σ- state shows anormal bending behavior due to a severe Fermi resonance which also gives rise to a large coupling between the bending and the Fe-C stretching motions, even though the corresponding third order force constant is small. The Yamada-Winnewisser quasi-linearity parameter γ0 is calculated to be -1.00 and -0.90, values characteristic for a linear molecule, for the X ˜ 3Σ- and a ˜ 5Σ- states, respectively. The ro-vibrationally averaged structures of the X ˜ 3Σ- state are discussed in detail and it is

  2. CO dimer: new potential energy surface and rovibrational calculations.

    PubMed

    Dawes, Richard; Wang, Xiao-Gang; Carrington, Tucker

    2013-08-15

    The spectrum of CO dimer was investigated by solving the rovibrational Schrödinger equation on a new potential energy surface constructed from coupled-cluster ab initio points. The Schrödinger equation was solved with a Lanczos algorithm. Several 4D (rigid monomer) global ab initio potential energy surfaces (PESs) were made using a previously reported interpolating moving least-squares (IMLS) fitting procedure specialized to describe the interaction of two linear fragments. The potential has two nonpolar minima giving rise to a complicated set of energy level stacks, which are very sensitive to the shapes and relative depths of the two wells. Although the CO dimer has defied previous attempts at an accurate purely ab initio description our best surface yields results in good agreement with experiment. Root-mean-square (rms) fitting errors of less than 0.1 cm(-1) were obtained for each of the fits using 2226 ab initio data at different levels. This allowed direct assessment of the quality of various levels of ab initio theory for prediction of spectra. Our tests indicate that standard CCSD(T) is slow to converge the interaction energy even when sextuple zeta bases as large as ACV6Z are used. The explicitly correlated CCSD(T)-F12b method was found to recover significantly more correlation energy (from singles and doubles) at the CBS limit. Correlation of the core-electrons was found to be important for this system. The best PES was obtained by extrapolation of calculations at the CCSD(T)(AE)-F12b/CVnZ-F12 (n = 3,4) levels. The calculated energy levels were compared to 105 J ≤ 10 levels from experiment. The rms error for 68 levels with J ≤ 6 is only 0.29 cm(-1). The calculated energy levels were assigned stack labels using several tools. New stacks were found. One of them, stack y1, has an energy lower than many previously known stacks and may be observable.

  3. TPD-based evaluation of near threshold mono-energetic proton energies for the (7)Li(p,n)(7)Be production of neutrons for BNCT.

    PubMed

    Bengua, Gerard; Kobayashi, Tooru; Tanaka, Kenichi; Nakagawa, Yoshinobu; Unesaki, Hironobu

    2006-08-21

    An evaluation of mono-energetic proton energies ranging from 1.885 MeV to 1.920 MeV was carried out to determine the viability of these near threshold energies in producing neutrons for BNCT via the (7)Li(p,n)(7)Be reaction. Neutron fields generated at these proton energies were assessed using the treatable protocol depth (TPD) and the maximum TPD (TPD(max)) as evaluation indices. The heavy charged particle (HCP) dose rate to tumour was likewise applied as a figure of merit in order to account for irradiation time and required proton current. Incident proton energies closer to the reaction threshold generated deeper TPDs compared to higher energy protons when no boron dose enhancers (BDE) were placed in the irradiation field. Introducing a BDE resulted in improved TPDs for high proton energies but their achievable TPD(max) were comparatively lower than that obtained for lower proton energies. In terms of the HCP dose rate to tumour, higher proton energies generated neutron fields that yielded higher dose rates both at TPD(max) and at fixed depths of comparison. This infers that higher currents are required to deliver the prescribed treatment dose to tumours for proton beams with energies closer to the (7)Li(p,n)(7)Be reaction threshold and more achievable proton currents of around 10 mA or less for proton energies from 1.900 MeV and above. The dependence on incident proton energy of the TPD, TPD(max) and the HCP dose rate to tumour with respect to the (10)B concentration in tumour and healthy tissues were also clarified in this study. Increasing the (10)B concentration in tumour while maintaining a constant T/N ratio resulted in deeper TPD(max) where a greater change in TPD(max) was obtained for proton energies closer to the (7)Li(p,n)(7)Be reaction threshold. The HCP dose rates to tumour for all proton energies also went up, with the higher proton energies benefiting more from the increased (10)B concentration.

  4. Evaluation of the characteristics of boron-dose enhancer (BDE) materials for BNCT using near threshold 7Li(p,n)7Be direct neutrons.

    PubMed

    Bengua, Gerard; Kobayashi, Tooru; Tanaka, Kenichi; Nakagawa, Yoshinobu

    2004-03-07

    The characteristics of a number of candidate boron-dose enhancer (BDE) materials for boron neutron capture therapy (BNCT) using near threshold 7Li(p,n)7Be direct neutrons were evaluated based on the treatable protocol depth (TPD), defined in this paper. Simulation calculations were carried out by means of MCNP-4B transport code for candidate BDE materials, namely, (C2H4)n, (C2H3F)n, (C2H2F2)n, (C2HF3)n, (C2D4)n, (C2F4)n, beryllium metal, graphite, D2O and 7LiF. Dose protocols applied were those used for intra-operative BNCT treatment for brain tumour currently used in Japan. The maximum TPD (TPDmax) for each BDE material was found to be between 4 cm and 5 cm in the order of (C2H4)n < (C2H3F)n < (C2H2F2)n < (C2HF3)n < beryllium metal < (C2D4)n < graphite < (C2F4)n < D2O < 7LiF. Based on the small and arbitrary variations in the TPDmax for these materials, an explicit advantage of a candidate BDE material could not be established from the TPDmax alone. The dependence of TPD on BDE thickness was found to be influenced by the type of BDE material. For materials with hydrogen, sharp variations in TPD were observed, while those without hydrogen exhibited more moderate fluctuations in TPD as the BDE thickness was varied. The BDE thickness corresponding to TPDmax (BDE(TPDmax)) was also found to depend on the type of BDE material used. Thicker BDE(TPDmax), obtained mostly for BDE materials without hydrogen, significantly reduced the dose rates within the phantom. The TPDmax, the dependence of TPD on BDE thickness and the BDE (TPDmax) were ascertained as appropriate optimization criteria in choosing suitable BDE materials for BNCT. Among the candidate BDE materials considered in this study. (C2H4)n was judged as the suitable material for near-surface tumours and beryllium metal for deeper tumours based on these optimization criteria and other practical considerations.

  5. Rovibrational bound states of SO2 isotopologues. II: Total angular momentum J = 11-20

    NASA Astrophysics Data System (ADS)

    Kumar, Praveen; Poirier, Bill

    2015-11-01

    In a two-part series, the rovibrational bound states of SO2 are investigated in comprehensive detail, for all four stable sulfur isotopes 32-34,36S. All low-lying rovibrational energy levels-both permutation-symmetry-allowed and not allowed-are computed, for all values of total angular momentum in the range J = 0-20. The calculations have carried out using the ScalIT suite of parallel codes. The present study (Paper II) examines the J = 11-20 rovibrational levels, providing symmetry and rovibrational labels for every computed state, relying on a new lambda-doublet splitting technique to make completely unambiguous assignments. Isotope shifts are analyzed, as is the validity of "J-shifting" as a predictor of rotational fine structure. Among other ramifications, this work will facilitate understanding of mass-independent fractionation of sulfur isotopes (S-MIF) observed in the Archean rock record-particularly as this may have arisen from self shielding. S-MIF, in turn is highly relevant in the broader context of understanding the "oxygen revolution".

  6. Rovibrational intensities and electric dipole moment function of the X2 Pi hydroxyl radical

    NASA Technical Reports Server (NTRS)

    Chackerian, C., Jr.; Goorvitch, D.; Benidar, A.; Farrenq, R.; Guelachvili, G.; Martin, P. M.; Abrams, M. C.; Davis, S. P.

    1992-01-01

    Recent work aimed at determining the absolute rovibrational transition intensities for the ground electronic state of the hydroxyl radical is reviewed. Two new sets of Fourier transform emission spectra of OH are described which were recorded at the University of Paris and at the Kitt Peak National Solar Observatory.

  7. Rovibrational Spectrum of the Ar-NO Complex in 5.3 μm Region

    NASA Astrophysics Data System (ADS)

    Duan, Chuanxi

    2017-06-01

    The rovibrational spectrum of the open-shell complex Ar-NO was recorded in the 1870-1892 \\wn range with a segmented rapid-scan pulsed supersonic jet infrared absorption spectrometer based on distributed-feedback quantum cascade lasers. Four b-type subbands were observed. The progress on the rotational analysis will be presented.

  8. Rovibrationally-resolved photodissociation of NH and application to the solar UV opacity

    NASA Astrophysics Data System (ADS)

    Shen, G.; Kuri, A.; Fontenla, J. M.; Stancil, P. C.; Wang, J. G.

    2014-05-01

    Rovibrationally-resolved photodissociation cross sections of NH have been evaluated using a combination of ab initio and experimentally derived potential curves and dipole transition moments. Here we present results for the three electronic transitions: 23Σ- <-- X3Σ- , 23 Π <-- X3Σ- , A3 Π <-- X3Σ- . Partial cross sections for transitions from all 577 rovibrational levels obtained theoretically for the ground electronic state X3Σ- , were computed for a wavelength range that extends from 500Å to the dissociation threshold for each particular rovibrational level. Assuming a thermal Boltzmann distribution of the rovibrational levels in X3Σ- , LTE cross sections are presented for gas temperatures between 500 and 10000 K. For applications to cold interstellar gas, cross sections for X3Σ- (v = 0 , J = 0) to 23Σ- and 23 Π dominate, but for the high density and temperature conditions in stellar atmospheres, the LTE cross section to the A3 Π becomes competitive. Explicit application of the cross sections to the solar UV opacity will be presented. In particular, the NH photodissociation opacity is found to affect the non-LTE behavior of some species such as Cr I and V I. The work at UGA was partially supported by NASA grant HST-AR-11776.01-A. The work of JMF was supported by NASA LWS grant NNX09AJ22G. GS acknowledges travel support by the International Cooperation and Exchange Foundation of CAEP.

  9. Understanding nuclear motions in molecules: Derivation of Eckart frame ro-vibrational Hamiltonian operators via a gateway Hamiltonian operator

    SciTech Connect

    Szalay, Viktor

    2015-05-07

    A new ro-vibrational Hamiltonian operator, named gateway Hamiltonian operator, with exact kinetic energy term, T-hat, is presented. It is in the Eckart frame and it is of the same form as Watson’s normal coordinate Hamiltonian. However, the vibrational coordinates employed are not normal coordinates. The new Hamiltonian is shown to provide easy access to Eckart frame ro-vibrational Hamiltonians with exact T-hat given in terms of any desired set of vibrational coordinates. A general expression of the Eckart frame ro-vibrational Hamiltonian operator is given and some of its properties are discussed.

  10. The Effect of Approximating Some Molecular Integrals in Coupled-Cluster Calculations: Fundamental Frequencies and Rovibrational Spectroscopic Constants of Cyclopropenylidene

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Dateo, Christopher E.

    2005-01-01

    The singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, denoted CCSD(T), has been used, in conjunction with approximate integral techniques, to compute highly accurate rovibrational spectroscopic constants of cyclopropenylidene, C3H2. The approximate integral technique was proposed in 1994 by Rendell and Lee in order to avoid disk storage and input/output bottlenecks, and today it will also significantly aid in the development of algorithms for distributed memory, massively parallel computer architectures. It is shown in this study that use of approximate integrals does not impact the accuracy of CCSD(T) calculations. In addition, the most accurate spectroscopic data yet for C3H2 is presented based on a CCSD(T)/cc-pVQZ quartic force field that is modified to include the effects of core-valence electron correlation. Cyclopropenylidene is of great astronomical and astrobiological interest because it is the smallest aromatic ringed compound to be positively identified in the interstellar medium, and is thus involved in the prebiotic processing of carbon and hydrogen. The singles and doubles coupled-cluster method that includes a perturbational estimate of

  11. The Effect of Approximating Some Molecular Integrals in Coupled-Cluster Calculations: Fundamental Frequencies and Rovibrational Spectroscopic Constants of Cyclopropenylidene

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Dateo, Christopher E.

    2005-01-01

    The singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, denoted CCSD(T), has been used, in conjunction with approximate integral techniques, to compute highly accurate rovibrational spectroscopic constants of cyclopropenylidene, C3H2. The approximate integral technique was proposed in 1994 by Rendell and Lee in order to avoid disk storage and input/output bottlenecks, and today it will also significantly aid in the development of algorithms for distributed memory, massively parallel computer architectures. It is shown in this study that use of approximate integrals does not impact the accuracy of CCSD(T) calculations. In addition, the most accurate spectroscopic data yet for C3H2 is presented based on a CCSD(T)/cc-pVQZ quartic force field that is modified to include the effects of core-valence electron correlation. Cyclopropenylidene is of great astronomical and astrobiological interest because it is the smallest aromatic ringed compound to be positively identified in the interstellar medium, and is thus involved in the prebiotic processing of carbon and hydrogen. The singles and doubles coupled-cluster method that includes a perturbational estimate of

  12. Alpha-decay branching ratios of near-threshold states in 19Ne and the astrophysical rate of 15O(α,γ)19Ne

    NASA Astrophysics Data System (ADS)

    Davids, B.; van den Berg, A. M.; Dendooven, P.; Fleurot, F.; Hunyadi, M.; de Huu, M. A.; Rehm, K. E.; Segel, R. E.; Siemssen, R. H.; Wilschut, H. W.; Wörtche, H. J.; Wuosmaa, A. H.

    2003-05-01

    The 15O(α, γ)19Ne reaction is one of two routes for breakout from the hot CNO cycles into the rp process in accreting neutron stars. Its astrophysical rate depends critically on the decay properties of excited states in 19Ne lying just above the 15O + α threshold. We have measured the α-decay branching ratios for these states using the p(21Ne,t)19Ne reaction at 43 MeV/u.

  13. Ab Initio Effective Rovibrational Hamiltonians for Non-Rigid Molecules via Curvilinear VMP2

    NASA Astrophysics Data System (ADS)

    Changala, Bryan; Baraban, Joshua H.

    2017-06-01

    Accurate predictions of spectroscopic constants for non-rigid molecules are particularly challenging for ab initio theory. For all but the smallest systems, ``brute force'' diagonalization of the full rovibrational Hamiltonian is computationally prohibitive, leaving us at the mercy of perturbative approaches. However, standard perturbative techniques, such as second order vibrational perturbation theory (VPT2), are based on the approximation that a molecule makes small amplitude vibrations about a well defined equilibrium structure. Such assumptions are physically inappropriate for non-rigid systems. In this talk, we will describe extensions to curvilinear vibrational Møller-Plesset perturbation theory (VMP2) that account for rotational and rovibrational effects in the molecular Hamiltonian. Through several examples, we will show that this approach provides predictions to nearly microwave accuracy of molecular constants including rotational and centrifugal distortion parameters, Coriolis coupling constants, and anharmonic vibrational and tunneling frequencies.

  14. Aspects of the Eckart frame ro-vibrational kinetic energy operator.

    PubMed

    Szalay, Viktor

    2015-08-14

    A most decisive part of developing the Eckart frame ro-vibrational kinetic energy operator (KEO) in terms of curvilinear internal coordinates is the introduction of vibrational displacements obeying the Eckart conditions. It is examined here, how such displacements may be constructed by orthogonal and nonorthogonal transformations, and how they can be employed in developing the KEO. In particular, it is shown analytically, by term by term comparison, that the Eckart KEOs obtained by employing Pickett's method and the gateway Hamiltonian method are equivalent. That is, although it may appear in the form of very different expressions, the general, exact ro-vibrational Eckart frame KEO is unique. As side result, it has been shown that the simple formula of the pseudo-potential derived by Watson for the exact KEO given in normal coordinates applies to any Eckart frame KEO, irrespective of the choice of the vibrational coordinates.

  15. Creation of Ultracold 87Rb 133Cs Molecules in the Rovibrational Ground State

    NASA Astrophysics Data System (ADS)

    Molony, Peter K.; Gregory, Philip D.; Ji, Zhonghua; Lu, Bo; Köppinger, Michael P.; Le Sueur, C. Ruth; Blackley, Caroline L.; Hutson, Jeremy M.; Cornish, Simon L.

    2014-12-01

    We report the creation of a sample of over 1000 ultracold 87Rb 133Cs molecules in the lowest rovibrational ground state, from an atomic mixture of 87Rb and 133Cs, by magnetoassociation on an interspecies Feshbach resonance followed by stimulated Raman adiabatic passage (STIRAP). We measure the binding energy of the RbCs molecule to be h c ×3811.576 (1 ) cm-1 and the |v''=0 ,J''=0 ⟩ to |v''=0 ,J''=2 ⟩ splitting to be h ×2940.09 (6 ) MHz . Stark spectroscopy of the rovibrational ground state yields an electric dipole moment of 1.225(3)(8) D, where the values in parentheses are the statistical and systematic uncertainties, respectively. We can access a space-fixed dipole moment of 0.355(2)(4) D, which is substantially higher than in previous work.

  16. Creation of ultracold ^{87}Rb^{133}Cs molecules in the rovibrational ground state.

    PubMed

    Molony, Peter K; Gregory, Philip D; Ji, Zhonghua; Lu, Bo; Köppinger, Michael P; Le Sueur, C Ruth; Blackley, Caroline L; Hutson, Jeremy M; Cornish, Simon L

    2014-12-19

    We report the creation of a sample of over 1000 ultracold ^{87}Rb^{133}Cs molecules in the lowest rovibrational ground state, from an atomic mixture of ^{87}Rb and ^{133}Cs, by magnetoassociation on an interspecies Feshbach resonance followed by stimulated Raman adiabatic passage (STIRAP). We measure the binding energy of the RbCs molecule to be hc×3811.576(1)  cm^{-1} and the |v^{''}=0,J^{''}=0⟩ to |v^{''}=0,J^{''}=2⟩ splitting to be h×2940.09(6)  MHz. Stark spectroscopy of the rovibrational ground state yields an electric dipole moment of 1.225(3)(8) D, where the values in parentheses are the statistical and systematic uncertainties, respectively. We can access a space-fixed dipole moment of 0.355(2)(4) D, which is substantially higher than in previous work.

  17. Aspects of the Eckart frame ro-vibrational kinetic energy operator

    NASA Astrophysics Data System (ADS)

    Szalay, Viktor

    2015-08-01

    A most decisive part of developing the Eckart frame ro-vibrational kinetic energy operator (KEO) in terms of curvilinear internal coordinates is the introduction of vibrational displacements obeying the Eckart conditions. It is examined here, how such displacements may be constructed by orthogonal and nonorthogonal transformations, and how they can be employed in developing the KEO. In particular, it is shown analytically, by term by term comparison, that the Eckart KEOs obtained by employing Pickett's method and the gateway Hamiltonian method are equivalent. That is, although it may appear in the form of very different expressions, the general, exact ro-vibrational Eckart frame KEO is unique. As side result, it has been shown that the simple formula of the pseudo-potential derived by Watson for the exact KEO given in normal coordinates applies to any Eckart frame KEO, irrespective of the choice of the vibrational coordinates.

  18. Raman investigation of ro-vibrational modes of interstitial H2 in Si

    NASA Astrophysics Data System (ADS)

    Koch, S. G.; Lavrov, E. V.; Weber, J.

    2012-08-01

    A Raman scattering study of ro-vibrational transitions Q(J) of the interstitial H2 in Si is presented. It is shown that the Q(2) mode of para hydrogen is coupled to the TAX phonon of Si. The mode appears in the spectra at temperatures above 200 K. The results presented also suggest that the Q(3) transition of ortho hydrogen is resonantly coupled to the OΓ phonon.

  19. Contracted basis Lanczos methods for computing numerically exact rovibrational levels of methane

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Carrington, Tucker

    2004-08-01

    We present a numerically exact calculation of rovibrational levels of a five-atom molecule. Two contracted basis Lanczos strategies are proposed. The first and preferred strategy is a two-stage contraction. Products of eigenfunctions of a four-dimensional (4D) stretch problem and eigenfunctions of 5D bend-rotation problems, one for each K, are used as basis functions for computing eigenfunctions and eigenvalues (for each K) of the Hamiltonian without the Coriolis coupling term, denoted H0. Finally, energy levels of the full Hamiltonian are calculated in a basis of the eigenfunctions of H0. The second strategy is a one-stage contraction in which energy levels of the full Hamiltonian are computed in the product contracted basis (without first computing eigenfunctions of H0). The two-stage contraction strategy, albeit more complicated, has the crucial advantage that it is trivial to parallelize the calculation so that the CPU and memory costs are independent of J. For the one-stage contraction strategy the CPU and memory costs of the difficult part of the calculation scale linearly with J. We use the polar coordinates associated with orthogonal Radau vectors and spherical harmonic type rovibrational basis functions. A parity-adapted rovibrational basis suitable for a five-atom molecule is proposed and employed to obtain bend-rotation eigenfunctions in the first step of both contraction methods. The effectiveness of the two methods is demonstrated by calculating a large number of converged J=1 rovibrational levels of methane using a global potential energy surface.

  20. Contracted basis Lanczos methods for computing numerically exact rovibrational levels of methane.

    PubMed

    Wang, Xiao-Gang; Carrington, Tucker

    2004-08-15

    We present a numerically exact calculation of rovibrational levels of a five-atom molecule. Two contracted basis Lanczos strategies are proposed. The first and preferred strategy is a two-stage contraction. Products of eigenfunctions of a four-dimensional (4D) stretch problem and eigenfunctions of 5D bend-rotation problems, one for each K, are used as basis functions for computing eigenfunctions and eigenvalues (for each K) of the Hamiltonian without the Coriolis coupling term, denoted H0. Finally, energy levels of the full Hamiltonian are calculated in a basis of the eigenfunctions of H0. The second strategy is a one-stage contraction in which energy levels of the full Hamiltonian are computed in the product contracted basis (without first computing eigenfunctions of H0). The two-stage contraction strategy, albeit more complicated, has the crucial advantage that it is trivial to parallelize the calculation so that the CPU and memory costs are independent of J. For the one-stage contraction strategy the CPU and memory costs of the difficult part of the calculation scale linearly with J. We use the polar coordinates associated with orthogonal Radau vectors and spherical harmonic type rovibrational basis functions. A parity-adapted rovibrational basis suitable for a five-atom molecule is proposed and employed to obtain bend-rotation eigenfunctions in the first step of both contraction methods. The effectiveness of the two methods is demonstrated by calculating a large number of converged J = 1 rovibrational levels of methane using a global potential energy surface.

  1. Quasiclassical description for rovibrational spectra of tetraatomics: the case of PH 3

    NASA Astrophysics Data System (ADS)

    Kozlovskii, Borislav M.; Petrov, Sergei V.

    2006-12-01

    Some new applications of so-called Rotational Energy Surface (RES) are discussed. As shown before, the method allows to discover some important qualitative features in rovibrational spectra of triatomics - e.g., energy level clustering. While trying to generalize the results, we developed a universal numerical procedure, allowing, particularly, to predict the formation of 6-fold energy clusters in spectra of PH 3 by quasiclassical means.

  2. State-selected chemical reaction dynamics at the S matrix level - Final-state specificities of near-threshold processes at low and high energies

    NASA Technical Reports Server (NTRS)

    Chatfield, David C.; Truhlar, Donald G.; Schwenke, David W.

    1992-01-01

    State-to-state reaction probabilities are found to be highly final-state specific at state-selected threshold energies for the reactions O + H2 yield OH + H and H + H2 yield H2 + H. The study includes initial rotational states with quantum numbers 0-15, and the specificity is especially dramatic for the more highly rotationally excited reactants. The analysis is based on accurate quantum mechanical reactive scattering calculations. Final-state specificity is shown in general to increase with the rotational quantum number of the reactant diatom, and the trends are confirmed for both zero and nonzero values of the total angular momentum.

  3. State-selected chemical reaction dynamics at the S matrix level - Final-state specificities of near-threshold processes at low and high energies

    NASA Technical Reports Server (NTRS)

    Chatfield, David C.; Truhlar, Donald G.; Schwenke, David W.

    1992-01-01

    State-to-state reaction probabilities are found to be highly final-state specific at state-selected threshold energies for the reactions O + H2 yield OH + H and H + H2 yield H2 + H. The study includes initial rotational states with quantum numbers 0-15, and the specificity is especially dramatic for the more highly rotationally excited reactants. The analysis is based on accurate quantum mechanical reactive scattering calculations. Final-state specificity is shown in general to increase with the rotational quantum number of the reactant diatom, and the trends are confirmed for both zero and nonzero values of the total angular momentum.

  4. Rovibrational molecular hamiltonian in mixed bond-angle and umbrella-like coordinates.

    PubMed

    Makarewicz, Jan; Skalozub, Alexander

    2007-08-16

    A new exact quantum mechanical rovibrational Hamiltonian operator for molecules exhibiting large amplitude inversion and torsion motions is derived. The derivation is based on a division of a molecule into two parts: a frame and a top. The nuclei of the frame only are used to construct a molecular system of axes. The inversion motion of the frame is described in the umbrella-like coordinates, whereas the torsion motion of the top is described by the nonstandard torsion angle defined in terms of the nuclear vectors and one of the molecular axes. The internal coordinates chosen take into account the properties of the inversion and torsion motions. Vibrational s and rotational Omega vectors obtained for the introduced internal coordinates determine the rovibrational tensor G defined by simple scalar products of these vectors. The Jacobian of the transformation from the Cartesian to the internal coordinates considered and the G tensor specify the rovibrational Hamiltonian. As a result, the Hamiltonian for penta-atomic molecules like NH2OH with one inverter is presented and a complete set of the formulas necessary to write down the Hamiltonian of more complex molecules, like NH2NH2 with two inverters, is reported. The approach considered is essentially general and sufficiently simple, as demonstrated by derivation of a polyatomic molecule Hamiltonian in polyspherical coordinates, obtained by other methods with much greater efforts.

  5. An exact variational method to calculate rovibrational spectra of polyatomic molecules with large amplitude motion

    NASA Astrophysics Data System (ADS)

    Yu, Hua-Gen

    2016-08-01

    We report a new full-dimensional variational algorithm to calculate rovibrational spectra of polyatomic molecules using an exact quantum mechanical Hamiltonian. The rovibrational Hamiltonian of system is derived in a set of orthogonal polyspherical coordinates in the body-fixed frame. It is expressed in an explicitly Hermitian form. The Hamiltonian has a universal formulation regardless of the choice of orthogonal polyspherical coordinates and the number of atoms in molecule, which is suitable for developing a general program to study the spectra of many polyatomic systems. An efficient coupled-state approach is also proposed to solve the eigenvalue problem of the Hamiltonian using a multi-layer Lanczos iterative diagonalization approach via a set of direct product basis set in three coordinate groups: radial coordinates, angular variables, and overall rotational angles. A simple set of symmetric top rotational functions is used for the overall rotation whereas a potential-optimized discrete variable representation method is employed in radial coordinates. A set of contracted vibrationally diabatic basis functions is adopted in internal angular variables. Those diabatic functions are first computed using a neural network iterative diagonalization method based on a reduced-dimension Hamiltonian but only once. The final rovibrational energies are computed using a modified Lanczos method for a given total angular momentum J, which is usually fast. Two numerical applications to CH4 and H2CO are given, together with a comparison with previous results.

  6. An exact variational method to calculate rovibrational spectra of polyatomic molecules with large amplitude motion.

    PubMed

    Yu, Hua-Gen

    2016-08-28

    We report a new full-dimensional variational algorithm to calculate rovibrational spectra of polyatomic molecules using an exact quantum mechanical Hamiltonian. The rovibrational Hamiltonian of system is derived in a set of orthogonal polyspherical coordinates in the body-fixed frame. It is expressed in an explicitly Hermitian form. The Hamiltonian has a universal formulation regardless of the choice of orthogonal polyspherical coordinates and the number of atoms in molecule, which is suitable for developing a general program to study the spectra of many polyatomic systems. An efficient coupled-state approach is also proposed to solve the eigenvalue problem of the Hamiltonian using a multi-layer Lanczos iterative diagonalization approach via a set of direct product basis set in three coordinate groups: radial coordinates, angular variables, and overall rotational angles. A simple set of symmetric top rotational functions is used for the overall rotation whereas a potential-optimized discrete variable representation method is employed in radial coordinates. A set of contracted vibrationally diabatic basis functions is adopted in internal angular variables. Those diabatic functions are first computed using a neural network iterative diagonalization method based on a reduced-dimension Hamiltonian but only once. The final rovibrational energies are computed using a modified Lanczos method for a given total angular momentum J, which is usually fast. Two numerical applications to CH4 and H2CO are given, together with a comparison with previous results.

  7. α-decay branching ratios of near-threshold states in 19Ne and the astrophysical rate of 15O(α,γ)19Ne

    NASA Astrophysics Data System (ADS)

    Davids, B.; van den Berg, A. M.; Dendooven, P.; Fleurot, F.; Hunyadi, M.; de Huu, M. A.; Rehm, K. E.; Segel, R. E.; Siemssen, R. H.; Wilschut, H. W.; Wörtche, H. J.; Wuosmaa, A. H.

    2003-01-01

    The 15O(α,γ)19Ne reaction is one of two routes for breakout from the hot CNO cycles into the rp process in accreting neutron stars. Its astrophysical rate depends critically on the decay properties of excited states in 19Ne lying just above the 15O+α threshold. We have measured the α-decay branching ratios for these states using the p(21Ne,t)19Ne reaction at 43 MeV/nucleon. Combining our measurements with previous determinations of the radiative widths of these states, we conclude that no significant breakout from the hot CNO cycle into the rp process in novas is possible via 15O(α,γ)19Ne, assuming that current models accurately represent their temperature and density conditions.

  8. Gas Phase Molecular Spectroscopy: Electronic Spectroscopy of Combustion Intermediates, Chlorine Azide kinetics, and Rovibrational Energy Transfer in Acetylene

    NASA Astrophysics Data System (ADS)

    Freel, Keith A.

    This dissertation is composed of three sections. The first deals with the electronic spectroscopy of combustion intermediates that are related to the formation of polycyclic aromatic hydrocarbons. Absorption spectra for phenyl, phenoxy, benzyl, and phenyl peroxy radicals were recorded using the technique of cavity ring-down spectroscopy. When possible, molecular constants, vibrational frequencies, and excited state lifetimes for these radicals were derived from these data. The results were supported by theoretical predictions. The second section presents a study of electron attachment to chlorine azide (ClN3) using a flowing-afterglow Langmuir-probe apparatus. Electron attachment rates were measured to be 3.5x10-8 and 4.5x10-8 cm3s-1 at 298 and 400 K respectively. The reactions of ClN3 with eighteen cations and seventeen anions were characterized. Rate constants were measured using a selected ion flow tube. The ionization energy (>9.6eV), proton affinity (713+/-41 kJ mol-1), and electron affinity (2.48+/-0.2 eV) for ClN 3 were determined from these data. The third section demonstrates the use of double resonance spectroscopy to observe state-selected rovibrational energy transfer from the first overtone asymmetric stretch of acetylene. The total population removal rate constants from various rotational levels of the (1,0,1,00,00) vibrational state were determined to be in the range of (9-17) x 10 -10 cm3s-1. Rotational energy transfer accounted for approximately 90% of the total removal rate from each state. Therefore, the upper limit of vibrational energy transfer from the (1,0,1,0 0,00) state was 10%.

  9. Fully state-selected VMI study of the near-threshold photodissociation of NO(2): variation of the angular anisotropy parameter.

    PubMed

    Matthews, S J; Willitsch, S; Softley, T P

    2007-11-14

    Velocity-map ion imaging (VMI) has been used to study the angular distribution of the NO fragment generated in the photodissociation of NO(2) at a variety of photolysis wavelengths. Images were recorded for the channels NO (2)Pi(1/2) (v = 0, J= 3/2, 11/2 and 21/2) + O ((3)P(2,1)), for excitation energies ranging from the onset (E(avl)/hc = 0 cm(-1)) to E(avl)/hc approximately 900 cm(-1). The angular anisotropy parameter beta was obtained as a function of available energy. Photofragment multiphoton ionization (PHOMPI) spectra were also recorded in the energy range E(avl)/hc = 0-300 cm(-1) for each of these channels. Large fluctuations of beta as a function of E(avl) were found in all observed dissociation channels. These variations are discussed in terms of the lifetimes of the originally photoexcited overlapping resonances in the A(2)B(2) state of NO(2), the dynamics of which are strongly influenced by nonadiabatic coupling with the X[combining tilde](2)A(1) state. The potential use of this photolysis process for production of cold oxygen atoms is discussed.

  10. Assessing the near threshold cross section of the 17O(n ,α )14C reaction by means of the Trojan horse method

    NASA Astrophysics Data System (ADS)

    Guardo, G. L.; Spitaleri, C.; Lamia, L.; Gulino, M.; La Cognata, M.; Tang, X.; deBoer, R.; Fang, X.; Goldberg, V.; Mrazek, J.; Mukhamedzhanov, A.; Notani, M.; Pizzone, R. G.; Rapisarda, G. G.; Sergi, M. L.; Wiescher, M.

    2017-02-01

    The study of the 17O(n ,α )14C reaction has been performed by means of the Trojan horse method (THM) applied to the quasifree 2H(17O,α 14C )1H reaction induced at a beam energy of 43.5 MeV. The THM allowed us to study the 8121-keV *18O resonant level, for which the previous THM investigation pointed out the ability of the method to overcome the centrifugal barrier suppression effects in the entrance channel. Here, in view of the developments of the method for resonant reactions, the detailed analysis of the performed experiment will be discussed, focusing on the extraction of the 8121-keV resonance strength for which no information is present in scientific literature. Moreover, the experimental results clearly show the excitation of the subthreshold level centered at -6 keV in the center-of-mass system, which is fundamental to determine the 17O(n ,α )14C reaction rate of astrophysical interest. Finally, a new recommended reaction rate is presented for future astrophysical application.

  11. Towards inclusion of excited vibrational states in ultracold molecule-molecule quantum scattering calculations

    NASA Astrophysics Data System (ADS)

    Ticknor, Christopher; Kendrick, Brian

    2016-05-01

    We report progress towards including excited vibrational states in quantum scattering calculations of NaK-NaK at ultracold temperatures. We systematically use all pair potentials to build a complete 4 body potential energy surface. We study this 4-body potential and the asymptotic ro-vibrational 2-body basis. This allows for a more complete interaction as two molecules approach each other. We study where and how vibrationally excited states influence the asymptotic 2-body ro-vibrational scattering potentials. This work is an intermediate step in performing the complete scattering calculations as we develop tools to bring together the long range, ultracold 2-body scattering problem and the short range 4-body quantum chemistry problem.

  12. The electronic states of thiophene studied by optical (VUV) absorption, near-threshold electron energy-loss (EEL) spectroscopy and ab initio multi-reference configuration interaction calculations

    NASA Astrophysics Data System (ADS)

    Palmer, Michael H.; Walker, Isobel C.; Guest, Martyn F.

    1999-03-01

    A reinvestigation and extension of the observed VUV and EEL spectrum of thiophene has been carried out, and the spectra assigned by means of high level multi-reference multi-root CI studies. It is concluded that each of two strong absorption bands centred around 5.5 and 7.0 eV respectively owe their intensity to excitation of two1ππ ∗ states, one each of symmetry 1A 1 and 1B 2. The range of calculated valence states of ππ ∗-type has been extended to include those from both 3b 1 and 2b 1. A wide range of Rydberg states derived from the five least bound orbitals has been obtained. The adiabatic IPs for the lowest series of cationic states with C 2 v symmetry, obtained by open shell SCF/CI studies, occur in the order: 1a 2-1< 3b 1-1< 11a 1-1< 7b 2-1< 2b 1-1. The equilibrium structures for the cations, when compared with the ground state under the same procedures, show that the order of the bond lengths C 2C 3 < C 3C 4 is reversed in the 2A 2 cation, while the SC bond length is markedly increased in the 2B 2 and 2B 1 (2b 1-1) cations. Significant distortions of the ring skeleton in the higher ions suggest that lower symmetry states are formed on ionisation. The present Green's function, TDA and CI calculations all lead to the same order of vertical IPs for the first nine IPs.

  13. Rovibrational Spectroscopy of Aluminum Carbonyl Clusters in Helium Nanodroplets

    NASA Astrophysics Data System (ADS)

    Liang, T.; Morrison, A. M.; Flynn, S. D.; Douberly, G. E.

    2011-06-01

    Helium nanodroplet isolation and a tunable quantum cascade laser are used to probe the fundamental CO stretch bands of Aluminum Carbonyl complexes, Al-(CO)N (n ≤ 5). The droplets are doped with single aluminum atoms via the resistive heating of an aluminum wetted tantalum wire. The downstream sequential pick-up of CO molecules leads to the rapid formation and cooling of Al-(CO)N clusters within the droplets. Near 1900 Cm-1, rotational fine structure is resolved in bands that are assigned to the CO stretch of a 2Π1/2 linear Al-CO species, and the asymmetric and symmetric CO stretch vibrations of a planar C2v Al-(CO)2 complex in a 2B1 electronic state. Bands corresponding to clusters with n ≥ 3 lack resolved rotational fine structure; nevertheless, the small frequency shifts from the n=2 bands indicate that these clusters consist of an Al-(CO)2 core with additional CO molecules attached via van-der-Waals interactions. A second n=2 band is observed near the CO stretch of Al-CO, indicating a local minimum on the n=2 potential consisting of an ``unreacted" Al-CO-(CO) cluster. The linewidth of this band is ˜0.5 cm-1, which is over 50 times broader than transitions within the Al-CO band. The additional broadening is consistent with a homogeneous mechanism corresponding to a rapid vibrational excitation induced reaction within the Al-CO-(CO) cluster to form the covalently bonded Al-(CO)2 complex. For the n=1,2 complexes, CCSD(T) calculations and Natural Bond Orbital (NBO) analyses are carried out to investigate the nature of the bonding in these complexes. The NBO calculations show that both π ``back" donation (from the occupied aluminum p-orbital into the π antibonding CO orbital) and σ donation (from CO into the empty aluminum p-orbitals) play a significant role in the bonding, analogous to transition metal carbonyl complexes. The large redshift of the CO stretch vibrations is consistent with this bonding analysis.

  14. Rovibrational states of the H2O-H2 complex: An ab initio calculation

    NASA Astrophysics Data System (ADS)

    van der Avoird, Ad; Nesbitt, David J.

    2011-01-01

    All bound rovibrational levels of the H2O-H2 dimer are calculated for total angular momentum J = 0-5 on two recent intermolecular potential surfaces reported by Valiron et al. [J. Chem. Phys. 129, 134306 (2008)] and Hodges et al. [J. Chem. Phys. 120, 710 (2004)] obtained through ab initio calculations. The method used handles correctly the large amplitude internal motions in this complex; it involves a discrete variable representation of the intermolecular distance coordinate R and a basis of coupled free rotor wave functions for the hindered internal rotations and the overall rotation of the dimer. The basis is adapted to the permutation symmetry associated with the para/ortho (p/o) nature of both H2O and H2 as well as to inversion symmetry. Dimers containing oH2 are more strongly bound than dimers with pH2, as expected, with dissociation energies D_0 of 33.57, 36.63, 53.60, and 59.04 cm^{-1}for pH2O-pH2, oH2O-pH2, pH2O-oH2, and oH2O-oH2, respectively, on the potential of Valiron et al. that corresponds to a binding energy D_e of 235.14 cm^{-1}. Rovibrational wave functions are computed as well and the nature of the bound states in the four different dimer species is discussed. Converged rovibrational levels on both potentials agree well with the high-resolution spectrum reported by Weida and Nesbitt [J. Chem. Phys. 110, 156 (1999)]; the hindered internal rotor model that was used to interpret this spectrum is qualitatively correct.

  15. Rovibrational coupling in molecular nitrogen at high temperature: An atomic-level study

    NASA Astrophysics Data System (ADS)

    Valentini, Paolo; Norman, Paul; Zhang, Chonglin; Schwartzentruber, Thomas E.

    2014-05-01

    This article contains an atomic-level numerical investigation of rovibrational relaxation in molecular nitrogen at high temperature (>4000 K), neglecting dissociation. We conduct our study with the use of pure Molecular Dynamics (MD) and Classical Trajectory Calculations (CTC) Direct Simulation Monte Carlo (DSMC), verified to produce statistically identical results at the conditions of interest here. MD and CTC DSMC solely rely on the specification of a potential energy surface: in this work, the site-site Ling-Rigby potential. Additionally, dissociation is prevented by modeling the N-N bond either as a harmonic or an anharmonic spring. The selected molecular model was shown to (i) recover the shear viscosity (obtained from equilibrium pure MD Green-Kubo calculations) of molecular nitrogen over a wide range of temperatures, up to dissociation; (ii) predict well the near-equilibrium rotational relaxation behavior of N2; (iii) reproduce vibrational relaxation times in excellent accordance with the Millikan-White correlation and previous semi-classical trajectory calculations in the low temperature range, i.e., between 4000 K and 10 000 K. By simulating isothermal relaxations in a periodic box, we found that the traditional two-temperature model assumptions become invalid at high temperatures (>10 000 K), due to a significant coupling between rotational and vibrational modes for bound states. This led us to add a modification to both the Jeans and the Landau-Teller equations to include a coupling term, essentially described by an additional relaxation time for internal energy equilibration. The degree of anharmonicity of the N2 bond determines the strength of the rovibrational coupling. Although neglecting N2 dissociation only provides a partial description of a nitrogen system at very high temperatures, high-energy trends for bound-bound transitions are essential to understand nonequilibrium gas flows, with possible implications on rovibration/chemistry interaction

  16. Rovibrational coupling in molecular nitrogen at high temperature: An atomic-level study

    SciTech Connect

    Valentini, Paolo Norman, Paul Zhang, Chonglin Schwartzentruber, Thomas E.

    2014-05-15

    This article contains an atomic-level numerical investigation of rovibrational relaxation in molecular nitrogen at high temperature (>4000 K), neglecting dissociation. We conduct our study with the use of pure Molecular Dynamics (MD) and Classical Trajectory Calculations (CTC) Direct Simulation Monte Carlo (DSMC), verified to produce statistically identical results at the conditions of interest here. MD and CTC DSMC solely rely on the specification of a potential energy surface: in this work, the site-site Ling-Rigby potential. Additionally, dissociation is prevented by modeling the N–N bond either as a harmonic or an anharmonic spring. The selected molecular model was shown to (i) recover the shear viscosity (obtained from equilibrium pure MD Green-Kubo calculations) of molecular nitrogen over a wide range of temperatures, up to dissociation; (ii) predict well the near-equilibrium rotational relaxation behavior of N{sub 2}; (iii) reproduce vibrational relaxation times in excellent accordance with the Millikan-White correlation and previous semi-classical trajectory calculations in the low temperature range, i.e., between 4000 K and 10 000 K. By simulating isothermal relaxations in a periodic box, we found that the traditional two-temperature model assumptions become invalid at high temperatures (>10 000 K), due to a significant coupling between rotational and vibrational modes for bound states. This led us to add a modification to both the Jeans and the Landau-Teller equations to include a coupling term, essentially described by an additional relaxation time for internal energy equilibration. The degree of anharmonicity of the N{sub 2} bond determines the strength of the rovibrational coupling. Although neglecting N{sub 2} dissociation only provides a partial description of a nitrogen system at very high temperatures, high-energy trends for bound-bound transitions are essential to understand nonequilibrium gas flows, with possible implications on rovibration

  17. Rovibrational energies, partition functions and equilibrium fractionation of the CO2 isotopologues

    NASA Astrophysics Data System (ADS)

    Cerezo, J.; Bastida, A.; Requena, A.; Zúñiga, J.

    2014-11-01

    Rovibrational energy levels, partition functions and relative abundances of the stable isotopologues of CO2 in gas phase at equilibrium are calculated using an empirical Morse-cosine potential energy surface (PES) refined by fitting to the updated pure (l2 = 0) vibrational frequencies observed for the main 12C16O2 isotopologue. The rovibrational energy levels are calculated variationally using a system of optimized hyperspherical normal coordinates, and from these the vibrational terms Gv and rotational constants Bv of the isotopologues are determined. The refined potential surface is shown to be clearly superior to the original potential surface, with the former reproducing the observed values of the spectroscopic constants Gv and Bv with accuracies of about 0.1 cm-1 and 0.00020 cm-1, respectively, for levels with l2 ≥ 0 up to 10,000 cm-1 above the ground state. The internal partition functions of the isotopologues are calculated by approximated direct summation over the rovibrational energies and compared with both previous partition sums and values obtained from analytical expressions based on the harmonic oscillator and rigid rotor models. The partition functions calculated by approximated direct summation are then used to determine the abundances of the CO2 isotopologues at thermodynamic equilibrium using the method developed by Wang et al. [74]. Significant variations in the relative abundances of some of the CO2 multiple substituted isotopologues at terrestrial temperatures with respect to those provided by the classical harmonic-based Urey theory are found, which may be of relevance in geochemical processes.

  18. Rovibrational states of the H2O-H2 complex: an ab initio calculation.

    PubMed

    van der Avoird, Ad; Nesbitt, David J

    2011-01-28

    All bound rovibrational levels of the H(2)O-H(2) dimer are calculated for total angular momentum J = 0-5 on two recent intermolecular potential surfaces reported by Valiron et al. [J. Chem. Phys. 129, 134306 (2008)] and Hodges et al. [J. Chem. Phys. 120, 710 (2004)] obtained through ab initio calculations. The method used handles correctly the large amplitude internal motions in this complex; it involves a discrete variable representation of the intermolecular distance coordinate R and a basis of coupled free rotor wave functions for the hindered internal rotations and the overall rotation of the dimer. The basis is adapted to the permutation symmetry associated with the para/ortho (p/o) nature of both H(2)O and H(2) as well as to inversion symmetry. Dimers containing oH(2) are more strongly bound than dimers with pH(2), as expected, with dissociation energies D(0) of 33.57, 36.63, 53.60, and 59.04 cm(-1)for pH(2)O-pH(2), oH(2)O-pH(2), pH(2)O-oH(2), and oH(2)O-oH(2), respectively, on the potential of Valiron et al. that corresponds to a binding energy D(e) of 235.14 cm(-1). Rovibrational wave functions are computed as well and the nature of the bound states in the four different dimer species is discussed. Converged rovibrational levels on both potentials agree well with the high-resolution spectrum reported by Weida and Nesbitt [J. Chem. Phys. 110, 156 (1999)]; the hindered internal rotor model that was used to interpret this spectrum is qualitatively correct.

  19. Sub-Doppler Rovibrational Spectroscopy of the H_3^+ Cation and Isotopologues

    NASA Astrophysics Data System (ADS)

    Markus, Charles R.; McCollum, Jefferson E.; Dieter, Thomas S.; Kocheril, Philip A.; McCall, Benjamin J.

    2017-06-01

    Molecular ions play a central role in the chemistry of the interstellar medium (ISM) and act as benchmarks for state of the art ab initio theory. The molecular ion H_3^+ initiates a chain of ion-neutral reactions which drives chemistry in the ISM, and observing it either directly or indirectly through its isotopologues is valuable for understanding interstellar chemistry. Improving the accuracy of laboratory measurements will assist future astronomical observations. H_3^+ is also one of a few systems whose rovibrational transitions can be predicted to spectroscopic accuracy (<1 cm^{-1}), and with careful treatment of adiabatic, nonadiabatic, and quantum electrodynamic corrections to the potential energy surface, predictions of low lying rovibrational states can rival the uncertainty of experimental measurements New experimental data will be needed to benchmark future treatment of these corrections. Previously we have reported 26 transitions within the fundamental band of H_3^+ with MHz-level uncertainties. With recent improvements to our overall sensitivity, we have expanded this survey to include additional transitions within the fundamental band and the first hot band. These new data will ultimately be used to predict ground state rovibrational energy levels through combination differences which will act as benchmarks for ab initio theory and predict forbidden rotational transitions of H_3^+. We will also discuss progress in measuring rovibrational transitions of the isotopologues H_2D^+ and D_2H^+, which will be used to assist in future THz astronomical observations. New experimental data will be needed to benchmark future treatment of these corrections. J. N. Hodges, A. J. Perry, P. A. Jenkins II, B. M. Siller, and B. J. McCall, J. Chem. Phys. (2013), 139, 164201. A. J. Perry, J. N. Hodges, C. R. Markus, G. S. Kocheril, and B. J. McCall, J. Mol. Spectrosc. (2015), 317, 71-73. A. J. Perry, C. R. Markus, J. N. Hodges, G. S. Kocheril, and B. J. McCall, 71st

  20. Computational study of the rovibrational spectrum of (CO2)2

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Carrington, Tucker; Dawes, Richard

    2016-12-01

    An interpolating moving least squares method is used to fit ab initio points to obtain an intermolecular potential energy surface (PES) for (CO2)2. The surface is used in conjunction with the symmetry-adapted Lanczos algorithm to compute rovibrational transition frequencies. The PES has four equivalent minima separated by barriers high enough that tunneling splittings are very small. The lowest energy pathway connecting the minima is a disrotatory channel. The calculations enable us to assign a combination band observed by Dehghany et al. (2010).

  1. Rovibrational hybrid fs/ps CARS using a volume Bragg grating for N₂ thermometry.

    PubMed

    Scherman, M; Nafa, M; Schmid, T; Godard, A; Bresson, A; Attal-Tretout, B; Joubert, P

    2016-02-01

    Coherent anti-Stokes Raman scattering (CARS) spectra of N2 in the hybrid femtosecond/picosecond regime have been recorded with 0.7  cm(-1) resolution. The Q-branch rovibrational structure has been resolved, making it suitable for gas-phase simultaneous rotational and vibrational thermometry applications. Resolving this spectral structure requires synchronization of a narrowband picosecond probe pulse with a broadband femtosecond pair of pump and Stokes pulses. It is achieved using a single femtosecond ytterbium-laser source and a volume Bragg grating in a compact experimental arrangement.

  2. Rapid-Adiabatic Control of Ro-Vibrational Populations in Polyatomic Molecules

    NASA Astrophysics Data System (ADS)

    Zak, Emil J.; Yachmenev, Andrey

    2017-06-01

    We present a simple method for control of ro-vibrational populations in polyatomic molecules in the presence of inhomogeneous electric fields [1]. Cooling and trapping of heavy polar polyatomic molecules has become one of the frontier goals in high-resolution molecular spectroscopy, especially in the context of parity violation measurement in chiral compounds [2]. A key step toward reaching this goal would be development of a robust and efficient protocol for control of populations of ro-vibrational states in polyatomic, often floppy molecules. Here we demonstrate a modification of the stark-chirped rapid-adiabatic-passage technique (SCRAP) [3], designed for achieving high levels of control of ro-vibrational populations over a selected region in space. The new method employs inhomogeneous electric fields to generate space- and time- controlled Stark-shifts of energy levels in molecules. Adiabatic passage between ro-vibrational states is enabled by the pump pulse, which raises the value of the Rabi frequency. This Stark-chirped population transfer can be used in manipulation of population differences between high-field-seeking and low-field-seeking states of molecules in the Stark decelerator [4]. Appropriate timing of voltages on electric rods located along the decelerator combined with a single pump laser renders our method as potentially more efficient than traditional Stark decelerator techniques. Simulations for NH_3 show significant improvement in effectiveness of cooling, with respect to the standard 'moving-potential' method [5]. At the same time a high phase-space acceptance of the molecular packet is maintained. E. J. Zak, A. Yachmenev (submitted). C. Medcraft, R. Wolf, M. Schnell, Angew. Chem. Int. Ed., 53, 43, 11656-11659 (2014) M. Oberst, H. Munch, T. Halfman, PRL 99, 173001 (2007). K. Wohlfart, F. Grätz, F. Filsinger, H. Haak, G. Meijer, J. Küpper, Phys. Rev. A 77, 031404(R) (2008). H. L. Bethlem, F. M. H. Crompvoets, R. T. Jongma, S. Y. T. van de

  3. Vibrationally Excited Molecular Hydrogen Near Herschel 36

    NASA Astrophysics Data System (ADS)

    Rachford, Brian L.; Snow, T. P.; Ross, T.

    2014-01-01

    We present the first high resolution UV spectra toward Herschel 36, a Trapezium-like system of high-mass stars contained within the Lagoon Nebula (M8, NGC 6523). The spectra reveal extreme ro-vibrational excitation of molecular hydrogen in material at a single velocity or very small range of velocities, most likely the largest ever seen in UV absorption spectra. While the velocities of the highly excited H2 lines are consistent within each observation, it appears that they underwent a ≈60 km s-1 redshift during the 3.6 years between observations. In neither case does the velocity of the highly excited material match the velocity of the bulk of the line-of-sight material which appears to mostly be in the foreground of M8. Recent work shows unusually excited CH and CH+ lines and several unusually broad Diffuse Interstellar Bands (DIBs) towards Herschel 36. Along with the H2 excitation, all of these findings appear to be related to the extreme environment within ˜0.1 pc of the massive young stellar system.

  4. Ghost features in Doppler-broadened spectra of rovibrational transitions in trapped HD+ ions

    NASA Astrophysics Data System (ADS)

    Patra, Sayan; Koelemeij, J. C. J.

    2017-02-01

    Doppler broadening plays an important role in laser rovibrational spectroscopy of trapped deuterated molecular hydrogen ions (HD+), even at the millikelvin temperatures achieved through sympathetic cooling by laser-cooled beryllium ions. Recently, Biesheuvel et al. (2016) presented a theoretical lineshape model for such transitions which not only considers linestrengths and Doppler broadening, but also the finite sample size and population redistribution by blackbody radiation, which are important in view of the long storage and probe times achievable in ion traps. Here, we employ the rate equation model developed by Biesheuvel et al. to theoretically study the Doppler-broadened hyperfine structure of the (v, L) : (0, 3) → (4, 2) rovibrational transition in HD+ at 1442 nm. We observe prominent yet hitherto unrecognized ghost features in the simulated spectrum, whose positions depend on the Doppler width, transition rates, and saturation levels of the hyperfine components addressed by the laser. We explain the origin and behavior of such features, and we provide a simple quantitative guideline to assess whether ghost features may appear. As such ghost features may be common to saturated Doppler-broadened spectra of rotational and vibrational transitions in trapped ions composed of partly overlapping lines, our work illustrates the necessity to use lineshape models that take into account all the relevant physics.

  5. The H(3) (+) rovibrational spectrum revisited with a global electronic potential energy surface.

    PubMed

    Velilla, Luis; Lepetit, Bruno; Aguado, Alfredo; Beswick, J Alberto; Paniagua, Miguel

    2008-08-28

    In this paper, we have computed the rovibrational spectrum of the H(3) (+) molecule using a new global potential energy surface, invariant under all permutations of the nuclei, that includes the long range electrostatic interactions analytically. The energy levels are obtained by a variational calculation using hyperspherical coordinates. From the comparison with available experimental results for low lying levels, we conclude that our accuracy is of the order of 0.1 cm(-1) for states localized in the vicinity of equilateral triangular configurations of the nuclei, and changes to the order of 1 cm(-1) when the system is distorted away from equilateral configurations. Full rovibrational spectra up to the H(+)+H(2) dissociation energy limit have been computed. The statistical properties of this spectrum (nearest neighbor distribution and spectral rigidity) show the quantum signature of classical chaos and are consistent with random matrix theory. On the other hand, the correlation function, even when convoluted with a smoothing function, exhibits oscillations which are not described by random matrix theory. We discuss a possible similarity between these oscillations and the ones observed experimentally.

  6. Variational calculations for the rovibrational states of Si 212C and Si 213C

    NASA Astrophysics Data System (ADS)

    Wang, Feng; von Nagy-Felsobuki, Ellak I.

    1996-11-01

    Rovibrational states of the ground electronic state of Si 212C and Si 213C isotopomers have been calculated variationally. The potential energy surface used in the calculations was obtained from an MP2/TZ2Pf ab initio surface of Barone et al. (V. Barone, P. Jensen and C. Minichino, J. Mol. Spectrosc., 154 (1992) 252) by applying the restrictions of 100° ⩽ α < 150°. The ab initio surface was refitted to a fourth-order polynomial with an Ogilvie-Tipping variable using a multi-dimensional least-squares procedure. The force field was then embedded in an Eckart-Watson vibration-rotation Hamiltonian, from which low-lying vibrational states and rovibrational states of Si 212C and Si 213C were obtained. The calculated vibrational states (100) and (001) of Si 212C and the 13C isotopic shifts agree well with a recent experiment (J.D. Presilla-Marquez and W.R.M. Graham, J. Chem. Phys., 95 (1991) 5612). Also, the calculations support the vibrational transition at 658.2 cm -1 found by Kafafi et al. (Z.H. Kafafi, R.H. Hauge, L. Fredin and J.L. Margrave, J. Chem. Phys., 87 (1983) 797). The rotational energies of these isotopomers for the lowest six vibrational states are given as are the rotational constants for Si 212C and Si 213C.

  7. Symmetry-Adapted Ro-vibrational Basis Functions for Variational Nuclear Motion Calculations: TROVE Approach.

    PubMed

    Yurchenko, Sergei N; Yachmenev, Andrey; Ovsyannikov, Roman I

    2017-09-12

    We present a general, numerically motivated approach to the construction of symmetry-adapted basis functions for solving ro-vibrational Schrödinger equations. The approach is based on the property of the Hamiltonian operator to commute with the complete set of symmetry operators and, hence, to reflect the symmetry of the system. The symmetry-adapted ro-vibrational basis set is constructed numerically by solving a set of reduced vibrational eigenvalue problems. In order to assign the irreducible representations associated with these eigenfunctions, their symmetry properties are probed on a grid of molecular geometries with the corresponding symmetry operations. The transformation matrices are reconstructed by solving overdetermined systems of linear equations related to the transformation properties of the corresponding wave functions on the grid. Our method is implemented in the variational approach TROVE and has been successfully applied to many problems covering the most important molecular symmetry groups. Several examples are used to illustrate the procedure, which can be easily applied to different types of coordinates, basis sets, and molecular systems.

  8. Rovibrational wave packet manipulation using shaped mid infrared femtosecond pulses toward quantum computing

    NASA Astrophysics Data System (ADS)

    Tsubouchi, Masaaki; Momose, Takamasa

    2007-06-01

    Laser pulse shaping which was developed in near infrared (NIR) has been recently extended into mid infrared (MIR: 3 -- 10 μm). In the presented study, the signal output (NIR: 1.1 -- 1.5 μm) of an optical parametric amplifier was shaped with a Dazzler, and mixed in a AgGaS2 crystal with the idler pulse to generate MIR pulses. Although the relation between the shapes of NIR and MIR light is complicated due to DFG process in the crystal with finite (2 mm) thickness, the shape of MIR light can be completely characterized by comparing with calculated profiles. The shaped MIR light which is well characterized can be used to manipulate rovibrational wave packet on the electronic ground state. We simulated the wave packet motion and its observable by solving the time-dependent Schr"odinger equation, and discussed how the shape of MIR pulse is transferred into the wave packet. Application of rovibrational wave packet manipulation to quantum computation will be discussed.

  9. Accurate quantum calculation of the bound and resonant rovibrational states of Li-(H2)

    NASA Astrophysics Data System (ADS)

    Xiao, Yingsheng; Poirier, Bill

    2005-03-01

    In a recent paper [B. Poirier, Chem. Phys. 308, 305 (2005)] a full-dimensional quantum method for computing the rovibrational dynamics of triatomic systems was presented, incorporating three key features: (1) exact analytical treatment of Coriolis coupling, (2) three-body "effective potential," and (3) a single bend angle basis for all rotational states. In this paper, these ideas are applied to the Li-(H2) electrostatic complex, to compute all of the rovibrational bound state energies, and a number of resonance energies and widths, to very high accuracy (thousandths of a wave number). This application is very challenging, owing to the long-range nature of the interaction and to narrow level spacings near dissociation. Nevertheless, by combining the present method with a G4 symmetry-adapted phase-space-optimized representation, only modest basis sizes are required for which the matrices are amenable to direct diagonalization. Several new bound levels are reported, as compared with a previous calculation [D. T. Chang, G. Surratt, G. Ristroff, and G. I. Gellene, J. Chem. Phys. 116, 9188 (2002)]. The resonances exhibit a clear-cut separation into shape and Feshbach varieties, with the latter characterized by extremely long lifetimes (microseconds or longer).

  10. Uniform rovibrational collisional N2 bin model for DSMC, with application to atmospheric entry flows

    NASA Astrophysics Data System (ADS)

    Torres, E.; Bondar, Ye. A.; Magin, T. E.

    2016-11-01

    A state-to-state model for internal energy exchange and molecular dissociation allows for high-fidelity DSMC simulations. Elementary reaction cross sections for the N2 (v, J)+ N system were previously extracted from a quantum-chemical database, originally compiled at NASA Ames Research Center. Due to the high computational cost of simulating the full range of inelastic collision processes (approx. 23 million reactions), a coarse-grain model, called the Uniform RoVibrational Collisional (URVC) bin model can be used instead. This allows to reduce the original 9390 rovibrational levels of N2 to 10 energy bins. In the present work, this reduced model is used to simulate a 2D flow configuration, which more closely reproduces the conditions of high-speed entry into Earth's atmosphere. For this purpose, the URVC bin model had to be adapted for integration into the "Rarefied Gas Dynamics Analysis System" (RGDAS), a separate high-performance DSMC code capable of handling complex geometries and parallel computations. RGDAS was developed at the Institute of Theoretical and Applied Mechanics in Novosibirsk, Russia for use by the European Space Agency (ESA) and shares many features with the well-known SMILE code developed by the same group. We show that the reduced mechanism developed previously can be implemented in RGDAS, and the results exhibit nonequilibrium effects consistent with those observed in previous 1D-simulations.

  11. Cryogenic exciter

    DOEpatents

    Bray, James William [Niskayuna, NY; Garces, Luis Jose [Niskayuna, NY

    2012-03-13

    The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.

  12. Near threshold studies of photoelectron satellites

    SciTech Connect

    Heimann, P.A.

    1986-11-01

    Photoelectron spectroscopy and synchrotron radiation have been used to study correlation effects in the rare gases: He, Ne, Ar, Kr, and Xe. Two kinds of time-of-flight electron analyzers were employed to examine photoionization very close to threshold and at higher kinetic energies. Partial cross sections and angular distributions have been measured for a number of photoelectron satellites. The shake-off probability has been determined at some inner-shell resonances. 121 refs., 28 figs., 13 tabs.

  13. Triple Photoionization of Neon Near Threshold

    NASA Astrophysics Data System (ADS)

    Bluett, J. B.; Whitfield, S. B.; Lukić, D.; Sellin, I. A.; Azuma, Y.; Wehlitz, R.

    2002-05-01

    The threshold behavior of the triple ionization cross-section of neon was investigated using monochromatized synchotron radiation and ion time-of-flight spectroscopy. The absolute cross-section is found to follow the Wannier power law(G.H. Wannier, Phys. Rev. 90), 817 (1953). in E with an exponent of 2.27 0.25 that has a range of validity of 5.5 eV. This result is consistent with the exponent of 2.162 predicted by theory and is also consistent with the findings of Samson and Angel(J.A.R. Samson and G.C. Angel, Phys. Lett. 61), 1584 (1988).. Further tests were performed over a range of 25 eV to determine the possibility of resonances and a secondary power law for energies above 5.5 eV.

  14. $DK$ and $D^* K$ scattering near threshold

    SciTech Connect

    Lang, C. B.; Leskovec, Luka; Mohler, Daniel; Prelovsek, Sasa; Woloshyn, R. M.

    2015-05-20

    We study the three $D_s$ quantum channels $J^P = 0^+$, $1^+$ and $2^+$ where experiments have identified the charm-strange states $D^*_{s0} (2317)$, $D_{s1}(2460)$, $D_{s1}(2536)$ near the $DK$ and $D^*K$ thresholds, and $D^*_{s2}(2573)$. We consider correlation functions for sets of $\\overline q q$ operators and, for $J^P = 0^+$, $1^+$, also the $DK$ and $D^*K$ meson-meson interpolators and determine for these cases values of the elastic scattering amplitude. Constructing the full set of correlators requires propagators which connect any pair of lattice sites. For one ensemble of gauge configurations ($32^3\\times 64$, $m_\\pi\\approx 156$ MeV) a stochastic distillation variant is employed and for another ensemble ($16^3\\times 32$, $m_\\pi\\approx 266$ MeV) we use the full distillation method. Both, $D^*_{s0} (2317)$ and $D_{s1}(2460)$, are found as bound states below threshold, whereas $D_{s1}(2536)$, and $D^*_{s2}(2573)$ are identified as narrow resonances close to the experimental masses.

  15. Solution of an infection model near threshold

    NASA Astrophysics Data System (ADS)

    Kessler, David A.; Shnerb, Nadav M.

    2007-07-01

    We study the susceptible-infected-recovered model of epidemics in the vicinity of the threshold infectivity. We derive the distribution of total outbreak size in the limit of large population size N . This is accomplished by mapping the problem to the first passage time of a random walker subject to a drift that increases linearly with time. We recover the scaling results of Ben-Naim and Krapivsky that the effective maximal size of the outbreak scales as N2/3 , with the average scaling as N1/3 , with an explicit form for the scaling function.

  16. Ro-vibrational quenching of CO (v = 1) by He impact in a broad range of temperatures: A benchmark study using mixed quantum/classical inelastic scattering theory.

    PubMed

    Semenov, Alexander; Ivanov, Mikhail; Babikov, Dmitri

    2013-08-21

    The mixed quantum/classical approach is applied to the problem of ro-vibrational energy transfer in the inelastic collisions of CO(v = 1) with He atom, in order to predict the quenching rate coefficient in a broad range of temperatures 5 < T < 2500 K. Scattering calculations are done in two different ways: direct calculations of quenching cross sections and, alternatively, calculations of the excitation cross sections plus microscopic reversibility. In addition, a symmetrized average-velocity method of Billing is tried. Combination of these methods allows reproducing experiment in a broad range of temperatures. Excellent agreement with experiment is obtained at 400 < T < 2500 K (within 10%), good agreement in the range 100 < T < 400 K (within 25%), and semi-quantitative agreement at 40 < T < 100 K(within a factor of 2). This study provides a stringent test of the mixed quantum/classical theory, because the vibrational quantum in CO molecule is rather large and the quencher is very light (He atom). For heavier quenchers and closer to dissociation limit of the molecule, the mixed quantum/classical theory is expected to work even better.

  17. Rovibrational spectroscopy using a kinetic energy operator in Eckart frame and the multi-configuration time-dependent Hartree (MCTDH) approach

    SciTech Connect

    Sadri, Keyvan Meyer, Hans-Dieter; Lauvergnat, David; Gatti, Fabien

    2014-09-21

    For computational rovibrational spectroscopy the choice of the frame is critical for an approximate separation of overall rotation from internal motions. To minimize the coupling between internal coordinates and rotation, Eckart proposed a condition [“Some studies concerning rotating axes and polyatomic molecules,” Phys. Rev. 47, 552–558 (1935)] and a frame that fulfills this condition is hence called an Eckart frame. A method is developed to introduce in a systematic way the Eckart frame for the expression of the kinetic energy operator (KEO) in the polyspherical approach. The computed energy levels of a water molecule are compared with those obtained using a KEO in the standard definition of the Body-fixed frame of the polyspherical approach. The KEO in the Eckart frame leads to a faster convergence especially for large J states and vibrationally excited states. To provide an example with more degrees of freedom, rotational states of the vibrational ground state of the trans nitrous acid (HONO) are also investigated.

  18. Isotopic and quantum-rovibrational-state effects for the ion-molecule reaction in the collision energy range of 0.03-10.00 eV.

    PubMed

    Xu, Yuntao; Xiong, Bo; Chang, Yih Chung; Ng, C Y

    2017-03-29

    We report detailed quantum-rovibrational-state-selected integral cross sections for the formation of H3O(+)via H-transfer (σHT) and H2DO(+)via D-transfer (σDT) from the reaction in the center-of-mass collision energy (Ecm) range of 0.03-10.00 eV, where (vvv) = (000), (100), and (020) and . The Ecm inhibition and rotational enhancement observed for these reactions at Ecm < 0.5 eV are generally consistent with those reported previously for H2O(+) + H2(D2) reactions. However, in contrast to the vibrational inhibition observed for the latter reactions at low Ecm < 0.5 eV, both the σHT and σDT for the H2O(+) + HD reaction are found to be enhanced by (100) vibrational excitation, which is not predicted by the current state-of-the-art theoretical dynamics calculations. Furthermore, the (100) vibrational enhancement for the H2O(+) + HD reaction is observed in the full Ecm range of 0.03-10.00 eV. The fact that vibrational enhancement is only observed for the reaction of H2O(+) + HD, and not for H2O(+) + H2(D2) reactions suggests that the asymmetry of HD may play a role in the reaction dynamics. In addition to the strong isotopic effect favoring the σHT channel of the H2O(+) + HD reaction at low Ecm < 0.5 eV, competition between the σHT and σDT of the H2O(+) + HD reaction is also observed at Ecm = 0.3-10.0 eV. The present state-selected study of the H2O(+) + HD reaction, along with the previous studies of the H2O(+) + H2(D2) reactions, clearly shows that the chemical reactivity of H2O(+) toward H2 (HD, D2) depends not only on Ecm, but also on the rotational and vibrational states of H2O(+)(X(2)B1). The detailed σHT and σDT values obtained here with single rovibrational-state selections of the reactant H2O(+) are expected to be valuable benchmarks for state-of-the-art theoretical calculations on the chemical dynamics of the title reaction.

  19. Studies on the P-branch spectral lines of rovibrational transitions of diatomic system.

    PubMed

    Sun, Weiguo; Fan, Qunchao; Li, Huidong; Feng, Hao

    2011-06-01

    An analytical formula is used to predict the accurate P-branch spectral lines of rovibrational transitions for diatomic systems. The formula is derived from elementary expression of molecular total energy by taking multiple spectral differences. It is not only reproduces the known experimental transition lines by using a group of fifteen known experimental transition data, but also predicts the accurate spectral lines that may not be available experimentally. The P-branch emission spectra of the (0,1), (0,2) and (0,3) bands of the B(2)∑(+)→X(2)∑(+) system in the (12)C(17)O(+) molecular ion are studied, and correct values of the unknown spectral lines up to J=80.5 for each band are predicted using the formula.

  20. Gmat. A software tool for the computation of the rovibrational G matrix

    NASA Astrophysics Data System (ADS)

    Castro, M. E.; Niño, A.; Muñoz-Caro, C.

    2009-07-01

    Gmat is a C++ program able to compute the rovibrational G matrix in molecules of arbitrary size. This allows the building of arbitrary rovibrational Hamiltonians. In particular, the program is designed to work with the structural results of potential energy hypersurface mappings computed in computer clusters or computational Grid environments. In the present version, 1.0, the program uses internal coordinates as vibrational coordinates, with the principal axes of inertia as body-fixed system. The main design implements a complete separation of the interface and functional parts of the program. The interface part permits the automatic reading of the molecular structures from the output files of different electronic structure codes. At present, Gamess and Gaussian output files are allowed. To such an end, use is made of the object orientation polymorphism characteristic. The functional part computes numerically the derivatives of the nuclear positions respect to the vibrational coordinates. Very accurate derivatives are obtained by using central differences embedded in a nine levels Richardson extrapolation procedure. Program summaryProgram title: Gmat Catalogue identifier: AECZ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECZ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 17 023 No. of bytes in distributed program, including test data, etc.: 274 714 Distribution format: tar.gz Programming language: Standard C++ Computer: All running Linux/Windows Operating system: Linux, Windows Classification: 16.2 Nature of problem: Computation of the rovibrational G matrix in molecules of any size. This allows the building of arbitrary rovibrational Hamiltonians. It must be possible to obtain the input data from the output files of standard electronic structure codes

  1. Variational Calculations of Ro-Vibrational Energy Levels and Transition Intensities for Tetratomic Molecules

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    A description is given of an algorithm for computing ro-vibrational energy levels for tetratomic molecules. The expressions required for evaluating transition intensities are also given. The variational principle is used to determine the energy levels and the kinetic energy operator is simple and evaluated exactly. The computational procedure is split up into the determination of one dimensional radial basis functions, the computation of a contracted rotational-bending basis, followed by a final variational step coupling all degrees of freedom. An angular basis is proposed whereby the rotational-bending contraction takes place in three steps. Angular matrix elements of the potential are evaluated by expansion in terms of a suitable basis and the angular integrals are given in a factorized form which simplifies their evaluation. The basis functions in the final variational step have the full permutation symmetries of the identical particles. Sample results are given for HCCH and BH3.

  2. Ro-vibrational averaging of the isotropic hyperfine coupling constant for the methyl radical

    SciTech Connect

    Adam, Ahmad Y.; Jensen, Per; Yachmenev, Andrey; Yurchenko, Sergei N.

    2015-12-28

    We present the first variational calculation of the isotropic hyperfine coupling constant of the carbon-13 atom in the CH{sub 3} radical for temperatures T = 0, 96, and 300 K. It is based on a newly calculated high level ab initio potential energy surface and hyperfine coupling constant surface of CH{sub 3} in the ground electronic state. The ro-vibrational energy levels, expectation values for the coupling constant, and its temperature dependence were calculated variationally by using the methods implemented in the computer program TROVE. Vibrational energies and vibrational and temperature effects for coupling constant are found to be in very good agreement with the available experimental data. We found, in agreement with previous studies, that the vibrational effects constitute about 44% of the constant’s equilibrium value, originating mainly from the large amplitude out-of-plane bending motion and that the temperature effects play a minor role.

  3. Variational Calculations of Ro-Vibrational Energy Levels and Transition Intensities for Tetratomic Molecules

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    A description is given of an algorithm for computing ro-vibrational energy levels for tetratomic molecules. The expressions required for evaluating transition intensities are also given. The variational principle is used to determine the energy levels and the kinetic energy operator is simple and evaluated exactly. The computational procedure is split up into the determination of one dimensional radial basis functions, the computation of a contracted rotational-bending basis, followed by a final variational step coupling all degrees of freedom. An angular basis is proposed whereby the rotational-bending contraction takes place in three steps. Angular matrix elements of the potential are evaluated by expansion in terms of a suitable basis and the angular integrals are given in a factorized form which simplifies their evaluation. The basis functions in the final variational step have the full permutation symmetries of the identical particles. Sample results are given for HCCH and BH3.

  4. Cooling and Infrared Emission due to Molecular Collisional Excitation in Astrophysical Environments

    NASA Astrophysics Data System (ADS)

    Stancil, Phillip

    2011-06-01

    Non-thermal popluations of molecules in a variety of astronomical environments, including photodissociation regions, X-ray dominated regions, and protoplanetary disks, are controlled by collisional excitation and quenching of their rovibrational levels. The important colliders are the dominant neutral species: H, He, and H2. Resulting emission lines are primary cooling transitions and can be observed by current and upcoming IR/submillimeter observatories including Spitzer, Herschel, SOFIA, and ALMA. Modeling these environments, however, requires large-scale computation of collisional excitation processes. The status, needs, and astrophysical applications for important molecular targets will be reviewed including H2, HD, CO, H2O, and NH3.

  5. Intermolecular potential and rovibrational states of the H2O-D2 complex

    NASA Astrophysics Data System (ADS)

    van der Avoird, Ad; Scribano, Yohann; Faure, Alexandre; Weida, Miles J.; Fair, Joanna R.; Nesbitt, David J.

    2012-05-01

    A five-dimensional intermolecular potential for H2O-D2 was obtained from the full nine-dimensional ab initio potential surface of Valiron et al. [P. Valiron, M. Wernli, A. Faure, L. Wiesenfeld, C. Rist, S. Kedžuch, J. Noga, J. Chem. Phys. 129 (2008) 134306] by averaging over the ground state vibrational wave functions of H2O and D2. On this five-dimensional potential with a well depth De of 232.12 cm-1 we calculated the bound rovibrational levels of H2O-D2 for total angular momentum J = 0-3. The method used to compute the rovibrational levels is similar to a scattering approach—it involves a basis of coupled free rotor wave functions for the hindered internal rotations and the overall rotation of the dimer—while it uses a discrete variable representation of the intermolecular distance coordinate R. The basis was adapted to the permutation symmetry associated with the para/ortho (p/o) nature of both H2O and D2, as well as to inversion symmetry. As expected, the H2O-D2 dimer is more strongly bound than its H2O-H2 isotopologue [cf. A. van der Avoird, D.J. Nesbitt, J. Chem. Phys. 134 (2011) 044314], with dissociation energies D0 of 46.10, 50.59, 67.43, and 73.53 cm-1 for pH2O-oD2, oH2O-oD2, pH2O-pD2, and oH2O-pD2. A rotationally resolved infrared spectrum of H2O-D2 was measured in the frequency region of the H2O bend mode. The ab initio calculated values of the rotational and distortion constants agree well with the values extracted from this spectrum.

  6. On the Lowest Ro-Vibrational States of Protonated Methane: Experiment and Analytical Model

    NASA Astrophysics Data System (ADS)

    Schmiedt, Hanno; Jensen, Per; Asvany, Oskar; Schlemmer, Stephan

    2016-06-01

    Protonated methane, CH_5^+, is the prototype of an extremely floppy molecule. To the best of our knowledge all barriers are surmountable in the rovibrational ground state; the large amount of zero-point vibrational energy leads to large amplitude motions for many degrees of freedom. Low resolution but broad band vibrational spectroscopy [1] revealed an extremely wide range of C-H stretching vibrations. Comparison with theoretical IR spectra supported the structural motif of a CH_3 tripod and an H_2 moiety, bound to the central carbon atom by a 3c2e bond. In a more dynamic picture the five protons surround the central carbon atom without significant restrictions on the H-C-H bending or H_n-C torsional motions. The large-amplitude internal motions preclude a simple theoretical description of the type possible for more conventional molecules, such as the related spherical-top methane molecule. Recent high-resolution ro-vibrational spectra obtained in cold ion trap experiments [2] show that the observed CH_5^+ transitions belong to a very well-defined energy level scheme describing the lowest rotational and vibrational states of this enigmatic molecule. Here we analyse the experimental ground state combination differences and associate them with the motional states of CH_5^+ allowed by Fermi-Dirac statistics. A model Hamiltonian for unrestricted internal rotations in CH_5^+ yields a simple analytical expression for the energy eigenvalues, expressed in terms of new quantum numbers describing the free internal rotation. These results are compared to the experimental combination differences and the validity of the model will be discussed together with the underlying assumptions. [1] O. Asvany, P. Kumar, I. Hegemann, B. Redlich, S. Schlemmer and D. Marx, Science 309, (2005) 1219-1222 [2] O. Asvany, K.M.T. Yamada, S. Brünken, A. Potapov, S. Schlemmer, Science 347 (2015) 1346-1349

  7. a Numerically Exact Full-Dimensional Calculation of Ro-Vibrational Levels of Water Dimer

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Carrington, Tucker

    2017-06-01

    We have developed a new method for computing numerically exact rovibrational levels of a Van der Waals dimer with flexible monomers and applied it to water dimer, a 12-dimensional cluster. % The method uses basis functions that are products of an inter-monomer function and an intra-monomer function. The inter-monomer function is a product of Wigner functions, used to study dimers within the rigid monomer approximation. The intra-monomer functions are monomer vibrational wavefunctions. % When the coupling between inter- and intra-monomer coordinates is weak, this new basis is very efficient and only a few monomer vibrational wavefunctions are necessary. The product structure of the basis makes it efficient to use the Lanczos algorithm to calculate eigenvalues and eigenfunctions of the Hamiltonian matrix. In particular, potential matrix-vector products are evaluated, without storing the potential on a full-dimensional grid, by adapting the F-matrix idea previously used to compute rovibrational levels of 5-atom and 6-atom molecules with a contracted basis and an iterative eigensolver. We have obtained numerically exact and converged inter-monomer energy levels and compare these with results obtained using the 6D + 6D adiabatic approach on the CCpol-8sf ab initio potential energy surface. We have also obtained the water bend levels and their shifts. We compare with results of the previous adiabatic calculation and experiment. X.-G. Wang and T. Carrington Jr. J. Chem. Phys. 119, 101 (2003) and 129, 234102 (2008). C. Leforestier, K. Szalewicz, and A. van der Avoid, J. Chem. Phys. 137, 014305 (2012).

  8. Resolving shocked and UV excited components of H2 emission in planetary nebulae with high-resolution near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Kaplan, Kyle; Dinerstein, Harriet L.; Jaffe, Daniel Thomas

    2016-06-01

    Planetary nebulae (PNe) form when low and intermediate-mass stars eject their outer layers into the ISM at the end of the AGB phase. Many PNe exhibit near-infrared (NIR) emission from molecular hydrogen (H2). This NIR emission arises from radiative decay out of excited rotation-vibration (rovibrational) states. The rovibrational states can be populated by excitation to higher electronic states through absorption of a far-UV photon followed by a radiative cascade to the electronic ground state, or by collisions (e.g., in a hot gas). The two processes populate the rovibrational levels of H2 differently, so the observed emergent emission spectrum provides an effective probe of the mechanisms that excite the H2. Many PNe display line intensity ratios that are intermediate between these two processes (Otsuka et al. 2013). With the advantages of the high spectral resolution (R~40000), broad wavelength coverage (1.45-2.45 μm), and high spatial resolution of the Immersion GRating Infrared Spectrometer (IGRINS, Park et al. 2014), we are able to differentiate components in position-velocity space: we see a slowly expanding UV-excited H2 shell in the PN M 1-11 and two faster moving “bullets” of thermalized H2 that we interpret as shocked gas from a bipolar outflow. We also present observations of several other PNe that exhibit similar morphologies of thermalized and UV-excited H2 components.

  9. Chirp excitation

    NASA Astrophysics Data System (ADS)

    Khaneja, Navin

    2017-09-01

    The paper describes the design of broadband chirp excitation pulses. We first develop a three stage model for understanding chirp excitation in NMR. We then show how a chirp π pulse can be used to refocus the phase of the chirp excitation pulse. The resulting magnetization still has some phase dispersion in it. We show how a combination of two chirp π pulses instead of one can be used to eliminate this dispersion, leaving behind a small residual phase dispersion. The excitation pulse sequence presented here allows exciting arbitrary large bandwidths without increasing the peak rf-amplitude. Experimental excitation profiles for the residual HDO signal in a sample of 99.5 % D2O are displayed as a function of resonance offset. Although methods presented in this paper have appeared elsewhere, we present complete analytical treatment that elucidates the working of these methods.

  10. An investigation of the {anti p}p {yields} {anti {Lambda}} {Lambda} and {anti p}p {yields} {anti {Sigma}}{sup 0} {Lambda} + c.c. reactions near threshold

    SciTech Connect

    Tayloe, R.; PS185 Collaboration

    1995-12-31

    Experiment PS 185 studies the production of antihyperon-hyperon pairs in antiproton-proton collisions at LEAR in the near-threshold energy region. The {ital {anti p} p} {r_arrow} {anti {Lambda}}{Lambda} reaction has been thoroughly studied by PS185 and many high-quality data have been reported. New results, including total and differential cross sections along with spin observables, are presented here for the channels {ital {anti p} p} {r_arrow} {anti {Lambda}}{Lambda} and {ital {anti p}p} {r_arrow} {anti {Sigma}}{sup 0}{Lambda} + c.c at incident lab antiproton momenta of 1.726 and 1. 771 GeV/c. The data from the relatively unstudied and complementary {ital {anti p}p} {r_arrow} {anti {Sigma}}{sup 0}{Lambda} + c.c channel is compared to that from {ital {anti p}p} {r_arrow} {anti {Lambda}}{Lambda} at similar energies above the reaction threshold.

  11. Exciter switch

    NASA Technical Reports Server (NTRS)

    Mcpeak, W. L.

    1975-01-01

    A new exciter switch assembly has been installed at the three DSN 64-m deep space stations. This assembly provides for switching Block III and Block IV exciters to either the high-power or 20-kW transmitters in either dual-carrier or single-carrier mode. In the dual-carrier mode, it provides for balancing the two drive signals from a single control panel located in the transmitter local control and remote control consoles. In addition to the improved switching capabilities, extensive monitoring of both the exciter switch assembly and Transmitter Subsystem is provided by the exciter switch monitor and display assemblies.

  12. Quantum chemical rovibrational data for the interstellar detection of c-C{sub 3}H{sup -}

    SciTech Connect

    Fortenberry, Ryan C.; Huang, Xinchuan; Crawford, T. Daniel; Lee, Timothy J. E-mail: Timothy.J.Lee@nasa.gov

    2014-12-01

    The anion chemistry of the interstellar medium (ISM) has almost exclusively been limited to linear hydrocarbons and cyanocarbons. Of the hydrocarbons, only the even n C {sub n}H{sup –} chains have been detected in the ISM, and lines hypothesized to originate with b-C{sub 3}H{sup –} have been conclusively linked to the corresponding cation, as originally claimed. However, no reason has yet been provided as to why other anions cannot form, and the cyclic form of C{sub 3}H{sup –} is actually the lowest-energy isomer on the anion's potential energy surface. As such, this work provides the necessary rovibrational reference data for the potential detection of this anion in the ISM or related laboratory experiments. Improvements over previously calculated rovibrational spectroscopic constants are contained herein along with graphical depictions of the pure rotational spectra at 100 K, 40 K, 20 K, and 2.7 K.

  13. A proposed new diagnostic for Herbig disc geometry. FWHM versus J of CO ro-vibrational lines

    NASA Astrophysics Data System (ADS)

    Hein Bertelsen, R. P.; Kamp, I.; van der Plas, G.; van den Ancker, M. E.; Waters, L. B. F. M.; Thi, W.-F.; Woitke, P.

    2016-05-01

    Aims: The CO ro-vibrational lines observed from Herbig group II discs are often seen to be broad, while the same lines observed from group I discs are often narrow. This difference is not well understood. In this paper we explore the underlying cause for this difference and provide a pathway for a better understanding of the geometry and structure of the inner discs around Herbig Ae/Be stars. Methods: High spectral resolution infrared spectra of CO ro-vibrational emission from six Herbig Ae/Be candidate stars were taken with the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES) at the Very Large Telescope (VLT). From these spectra, we produce individual and co-added CO ro-vibrational line profiles. We investigate line profile shape differences, and we explore the full width at half maximum (FWHM) variations with J quantum number in the context of disc geometry. Furthermore, we put our new sources into the context of earlier observed sources to study a large sample. For comparison, we also investigate the FWHM variations with J of modelled CO ro-vibrational lines from two typical disc geometries produced with the thermochemical disc modelling code ProDiMo. Results: For our new observations of CO ro-vibrational lines, we find that the FWHM of individual lines are in the range of 10-60 km s-1. We find both narrow and broad single-peaked emission lines, but only Hen 2-80 displays double-peaked emission lines. For HD 250550, the FWHM of the CO lines increases with J value, indicating a radially extended emitting region, while Hen 2-80 shows a constant FWHM versus J behaviour, indicating a narrow emitting region. This qualitatively agrees with the two different modelled disc geometries. Comparing dust and gas inner disc geometries (inferred by the spectral energy distribution (SED) and CO ro-vibrational emission) for the expanded sample of observed Herbig discs, we find no clear correspondence between the SED (spectral energy distribution) groups of the

  14. Symmetry-adapted tensorial formalism to model rovibrational and rovibronic spectra of molecules pertaining to various point groups

    NASA Astrophysics Data System (ADS)

    Boudon, V.; Champion, J.-P.; Gabard, T.; Loëte, M.; Michelot, F.; Pierre, G.; Rotger, M.; Wenger, Ch.; Rey, M.

    2004-12-01

    We present a short review on the tensorial formalism developed by the Dijon group to solve molecular spectroscopy problems. This approach, originally devoted to the rovibrational spectroscopy of highly symmetrical species (spherical tops) has been recently extended in several directions: quasi-spherical tops, some symmetric and asymmetric tops, and rovibronic spectroscopy of spherical tops in a degenerate electronic state. Despite its apparent complexity (heavy notations, quite complex mathematical tools), these group theoretical tensorial methods have a great advantage of flexibility: a systematic expansion of effective terms for any rovibrational/rovibronic problem up to a given order is automatically generated. Inclusion of all possible interaction terms for any polyad scheme is therefore easy. This makes such an approach suitable for many types of molecular problems, not only the most symmetric ones.

  15. General formulation of rovibrational kinetic energy operators and matrix elements in internal bond-angle coordinates using factorized Jacobians

    NASA Astrophysics Data System (ADS)

    Kopp, Wassja A.; Leonhard, Kai

    2016-12-01

    We show how inverse metric tensors and rovibrational kinetic energy operators in terms of internal bond-angle coordinates can be obtained analytically following a factorization of the Jacobian worked out by Frederick and Woywod. The structure of these Jacobians is exploited in two ways: On one hand, the elements of the metric tensor as well as its determinant all have the form ∑rmsin (αn) cos (βo) . This form can be preserved by working with the adjugate metric tensor that can be obtained without divisions. On the other hand, the adjugate can be obtained with less effort by exploiting the lower triangular structure of the Jacobians. Together with a suitable choice of the wavefunction, we avoid singularities and show how to obtain analytical expressions for the rovibrational kinetic energy matrix elements.

  16. High-power electron beam tests of a liquid-lithium target and characterization study of (7)Li(p,n) near-threshold neutrons for accelerator-based boron neutron capture therapy.

    PubMed

    Halfon, S; Paul, M; Arenshtam, A; Berkovits, D; Cohen, D; Eliyahu, I; Kijel, D; Mardor, I; Silverman, I

    2014-06-01

    A compact Liquid-Lithium Target (LiLiT) was built and tested with a high-power electron gun at Soreq Nuclear Research Center (SNRC). The target is intended to demonstrate liquid-lithium target capabilities to constitute an accelerator-based intense neutron source for Boron Neutron Capture Therapy (BNCT) in hospitals. The lithium target will produce neutrons through the (7)Li(p,n)(7)Be reaction and it will overcome the major problem of removing the thermal power >5kW generated by high-intensity proton beams, necessary for sufficient therapeutic neutron flux. In preliminary experiments liquid lithium was flown through the target loop and generated a stable jet on the concave supporting wall. Electron beam irradiation demonstrated that the liquid-lithium target can dissipate electron power densities of more than 4kW/cm(2) and volumetric power density around 2MW/cm(3) at a lithium flow of ~4m/s, while maintaining stable temperature and vacuum conditions. These power densities correspond to a narrow (σ=~2mm) 1.91MeV, 3mA proton beam. A high-intensity proton beam irradiation (1.91-2.5MeV, 2mA) is being commissioned at the SARAF (Soreq Applied Research Accelerator Facility) superconducting linear accelerator. In order to determine the conditions of LiLiT proton irradiation for BNCT and to tailor the neutron energy spectrum, a characterization of near threshold (~1.91MeV) (7)Li(p,n) neutrons is in progress based on Monte-Carlo (MCNP and Geant4) simulation and on low-intensity experiments with solid LiF targets. In-phantom dosimetry measurements are performed using special designed dosimeters based on CR-39 track detectors.

  17. Heuristic computation of the rovibrational G matrix in optimized molecule-fixed axes. Gmat 2.1

    NASA Astrophysics Data System (ADS)

    Castro, M. E.; Niño, A.; Muñoz-Caro, C.

    2010-08-01

    Gmat 2.1 is a program able to compute the rovibrational G matrix in different molecule-fixed axes extending the capabilities of Gmat 1.0. The present version is able to select optimal molecule-fixed axes minimizing the pure rotational kinetic elements, the rovibrational kinetic elements or both simultaneously. To such an end, it uses a hybrid minimization approach. Thus, it combines a global search heuristic based in simulated annealing with a gradient-free local minimization. As the previous version, the program handles the structural results of potential energy hypersurface mappings computed in computer clusters or computational Grid environments. However, since now more general molecule-fixed axes can be defined, a procedure is implemented to ensure the same minimum of the cost function is used in all the molecular structures. In addition, an algorithm for the unambiguous definition of the molecule-fixed axes orientation is used. Program summaryProgram title: Gmat 2.1 Catalogue identifier: AECZ_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECZ_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 52 555 No. of bytes in distributed program, including test data, etc.: 932 366 Distribution format: tar.gz Programming language: Standard ANSI C++ Computer: All Operating system: Linux, Windows Classification: 16.2 Catalogue identifier of previous version: AECZ_v1_0 Journal reference of previous version: Comput. Phys. Comm. 180 (2009) 1183 Does the new version supersede the previous version?: Yes Nature of problem: When building molecular rovibrational Hamiltonians, the kinetic terms depend on the molecule-fixed axes orientation. Thus, an appropriate orientation can significantly simplify the treatment of pure rotation and rovibrational coupling. The kinetic terms

  18. Rovibrational analysis of the ethylene isotopologue 13C2D4 by high-resolution Fourier transform infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Tan, T. L.; Gabona, M. G.; Godfrey, Peter D.; McNaughton, Don

    2015-01-01

    The Fourier transform infrared (FTIR) spectrum of the unperturbed a-type ν12 band of 13C2D4 was recorded at an unapodized resolution of 0.0063 cm-1 between 1000 and 1140 cm-1 for a rovibrational analysis. By assigning and fitting a total of 2068 infrared transitions using a Watson's A-reduced and S-reduced Hamiltonians in the Ir representation, rovibrational constants for the upper state (ν12 = 1) up to five quartic centrifugal distortion terms were derived for the first time. The root-mean-square (rms) deviation of the fits was 0.00034 cm-1 both in the A-reduction and S-reduction Hamiltonian. The ground state rovibrational constants of 13C2D4 in the A-reduced and S-reduced Hamiltonians were also determined for the first time by a fit of 985 combination-differences from the present infrared measurements, with rms deviation of 0.00036 cm-1. The ν12 band centre of 13C2D4 was at 1069.970824(17) cm-1 and at 1069.970799(17) cm-1 for the A-reduced and S-reduced Hamiltonians respectively. The ground state constants of 13C2D4 from this experimental work are in close agreement to those derived from theoretical calculations using the B3LYP/cc-pVTZ, MP2/cc-pVTZ, and CSSD(T)/cc-pVTZ levels of theory.

  19. Variational Calculations of IR Ro-Vibrational Spectra for Nitric Acid

    NASA Astrophysics Data System (ADS)

    Pavlyuchko, A. I.; Yurchenko, S. N.; Tennyson, J.

    2013-09-01

    To model the atmospheric composition of the potentially habitable planets, it is essential to have comprehensive data on the spectroscopic properties of the main molecular absorbers. This is especially true in the infrared region which is dominated by transitions of polyatomic molecules [1]. Nitric acid (HNO3) is an important constituent of the Earth atmosphere where it is a prominent bio-signature. Here we present simulations of the absorption spectra for HNO3. We have developed a variational method to solve the ro-vibrational Schrödinger equation for a general polyatomic molecule. The ro-vibrational Hamiltonian is given by [2] where the internal curvilinear vibrational coordinates qi are used to represent the displacements of the bond lengths and bond angles, ?ij(q) are elements of the matrix of the kinematic coefficients, t is the determinant of this matrix, 'a are the Euler angles, and μab(q) is the inverse matrix of the tensor of inertia. The potential energy function, V (q), is given by a fourthorder polynomial expansion in terms of Morse variables xi = 1 - e-iqi for the stretching coordinates and xi = qi for the bending coordinates. The dipole moment of the molecule is presented in the form of a Taylor series of the 2nd order in terms of qi. The parameters of the potential energy and the dipole moment functions of HNO3 were calculated by the quantum chemical method at the CCSD(T)/aug-cc-pVQZ level of theory. With this potential energy function, agreement between the calculated and experimental fundamental frequencies of vibrations is within 5 cm -1. The harmonic part of the potential function was then optimized by fitting to the experimental fundamental frequencies and used to simulate the IR spectra of HNO3. The results are in good agreement with the experimental data. The figure shows an example of the simulated spectra of HNO3 in the area of the strong Fermi resonance between the -5 and 2-9 bands along with an experimental counterpart. The resulting

  20. Numerically Exact Calculation of Rovibrational Levels of Cl^-H_2O

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Carrington, Tucker

    2014-06-01

    Large amplitude vibrations of Van der Waals clusters are important because they reveal large regions of a potential energy surface (PES). To calculate spectra of Van der Waals clusters it is common to use an adiabatic approximation. When coupling between intra- and inter-molecular coordinates is important non-adiabatic coupling cannot be neglected and it is therefore critical to develop and test theoretical methods that couple both types of coordinates. We have developed new product basis and contracted basis Lanczos methods for Van der Waals complexes and tested them by computing rovibrational energy levels of Cl^-H_2O. The new product basis is made of functions of the inter-monomer distance, Wigner functions that depend on Euler angles specifying the orientation of H_2O with respect to a frame attached to the inter-monomer Jacobi vector, basis functions for H_2O vibration, and Wigner functions that depend on Euler angles specifying the orientation of the inter-monomer Jacobi vector with respect to a space-fixed frame. An advantage of this product basis is that it can be used to make an efficient contracted basis by replacing the vibrational basis functions for the monomer with monomer vibrational wavefunctions. Due to weak coupling between intra- and inter-molecular coordinates, only a few tens of monomer vibrational wavefunctions are necessary. The validity of the two new methods is established by comparing energy levels with benchmark rovibrational levels obtained with polyspherical coordinates and spherical harmonic type basis functions. For all bases, product structure is exploited to calculate eigenvalues with the Lanczos algorithm. For Cl^-H_2O, we are able, for the first time, to compute accurate splittings due to tunnelling between the two equivalent C_s minima. We use the PES of Rheinecker and Bowman (RB). Our results are in good agreement with experiment for the five fundamental bands observed. J. Rheinecker and J. M. Bowman, J. Chem. Phys. 124 131102

  1. Exciting Pools

    ERIC Educational Resources Information Center

    Wright, Bradford L.

    1975-01-01

    Advocates the creation of swimming pool oscillations as part of a general investigation of mechanical oscillations. Presents the equations, procedure for deriving the slosh modes, and methods of period estimation for exciting swimming pool oscillations. (GS)

  2. Vibrationally Excited HCN around AFGL 2591: A Probe of Protostellar Structure

    NASA Astrophysics Data System (ADS)

    Veach, Todd J.; Groppi, Christopher E.; Hedden, Abigail

    2013-03-01

    Vibrationally excited molecules with submillimeter rotational transitions are potentially excellent probes of physical conditions near protostars. This study uses observations of the v = 1 and v = 2 ro-vibrational modes of HCN (4-3) to probe this environment. The presence or absence and relative strengths of these ro-vibrational lines probe the gas excitation mechanism and physical conditions in warm, dense material associated with protostellar disks. We present pilot observations from the Heinrich Hertz Submillimeter Telescope and follow-up observations from the Submillimeter Array. All vibrationally excited HCN (4-3) v = 0, v = 1, and v = 2 lines were observed. The existence of the three v = 2 lines at approximately equal intensity imply collisional excitation with a density of greater than (1010 cm-3) and a temperature of >1000 K for the emitting gas. This warm, high-density material should directly trace structures formed in the protostellar envelope and disk environment. Further, the line shapes of the v = 2 emission may suggest a Keplerian disk. This Letter demonstrates the utility of this technique which is of particular interest due to the recent inauguration of the Atacama Large Millimeter Array.

  3. VIBRATIONALLY EXCITED HCN AROUND AFGL 2591: A PROBE OF PROTOSTELLAR STRUCTURE

    SciTech Connect

    Veach, Todd J.; Groppi, Christopher E.; Hedden, Abigail

    2013-03-10

    Vibrationally excited molecules with submillimeter rotational transitions are potentially excellent probes of physical conditions near protostars. This study uses observations of the v = 1 and v = 2 ro-vibrational modes of HCN (4-3) to probe this environment. The presence or absence and relative strengths of these ro-vibrational lines probe the gas excitation mechanism and physical conditions in warm, dense material associated with protostellar disks. We present pilot observations from the Heinrich Hertz Submillimeter Telescope and follow-up observations from the Submillimeter Array. All vibrationally excited HCN (4-3) v = 0, v = 1, and v = 2 lines were observed. The existence of the three v = 2 lines at approximately equal intensity imply collisional excitation with a density of greater than (10{sup 10} cm{sup -3}) and a temperature of >1000 K for the emitting gas. This warm, high-density material should directly trace structures formed in the protostellar envelope and disk environment. Further, the line shapes of the v = 2 emission may suggest a Keplerian disk. This Letter demonstrates the utility of this technique which is of particular interest due to the recent inauguration of the Atacama Large Millimeter Array.

  4. A FFT Method for the Quasiclassical Selection of Initial Ro-Vibrational States of Triatomic Molecules

    NASA Technical Reports Server (NTRS)

    Eaker, Charles W.; Schwenke, David W.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    This paper describes the use of an exact fast Fourier transform (FFT) method to prepare specified vibrational-rotational states of triatomic molecules. The method determines the Fourier coefficients needed to describe the coordinates and momenta of a vibrating-rotating triatomic molecule. Once the Fourier coefficients of a particular state are determined, it is possible to easily generate as many random sets of initial cartesian coordinates and momenta as desired. All the members of each set will correspond to the particular vibrational-rotational state selected. For example, in the case of the ground vibrational state of a non-rotating water molecule, the calculated actions of 100 sets of initial conditions produced actions within 0.001 h(bar) of the specified quantization values and energies within 5 cm(sup -1) of the semiclassical eigenvalue. The numerical procedure is straightforward for states in which all the fundamental frequencies are independent. However for states for which the fundamental frequencies become commensurate (resonance states), there are additional complications. In these cases it is necessary to determine a new set of "fundamental" frequencies and to modify the quantization conditions. Once these adjustments are made, good results are obtained for resonance states. The major problems are in labelling the large number of Fourier coefficients and the presence of regions of chaotic motion. Results are presented for the vibrational states of H2O and HCN and the ro-vibrational states of H2O.

  5. The Ethyl Radical in Superfluid Helium Nanodroplets: Rovibrational Spectroscopy and AB Initio Calcluations

    NASA Astrophysics Data System (ADS)

    Raston, Paul L.; Moradi, Christopher P.; Agarwal, Jay; Turney, Justin. M.; Schaefer, Henry F. Schaefer, Iii; Douberly, Gary E.

    2013-06-01

    The ethyl radical has been isolated and spectroscopically characterized in ^4He nanodroplets. The five fundamental CH stretch bands are observed near 3 μm and have band origins shifted < 1 wn from those reported for the gas phase species. The symmetric CH_2 stretching band (ν_1) is rotationally resolved, revealing nuclear spin statistical weights predicted by G_{12} permutation-inversion group theory. A permanent electric dipole moment of 0.28 (2) D is obtained via the Stark spectrum of the ν_1 band. The four other CH stretch fundamental bands are broadened in helium droplets and lack rotational fine structure. The approximately 1-2 wn line widths for these bands are attributed to the homogeneous broadening associated with solvent-mediated rovibrational relaxation dynamics. In addition to these five fundamentals, three A_1' overtone/combination bands are observed and have resolved rotational substructure. These are assigned to the 2ν_{12}, ν_4+ν_6, and 2ν_6 bands through comparisons to anharmonic frequency computations at the CCSD(T)/cc-pVTZ level of theory. S. Davis, D. Uy, D. J. Nesbitt. J. Chem. Phys. 112, 1823-1834 (2000). T. Haber, A. C. Blair, D. J. Nesbitt, M. D. Schuder. J. Chem. Phys. 124, 054316 (2006).

  6. Rovibrational analysis of the XUV photodissociation of HeH{sup +} ions

    SciTech Connect

    Loreau, J.; Lecointre, J.; Urbain, X.; Vaeck, N.

    2011-11-15

    We investigate the dynamics of the photodissociation of the helium hydride ion HeH{sup +} by XUV radiation with the aim to establish a detailed comparison with a recent experimental work carried out at the FLASH free electron laser using both vibrationally hot and cold ions. We determine the corresponding rovibrational distributions using a dissociative charge transfer setup and the same source conditions as in the FLASH experiment. Using a nonadiabatic time-dependent wave-packet method, we calculate the partial photodissociation cross sections for the n=1-3 coupled electronic states of HeH{sup +}. We find good agreement with the experiment for the cross section into the He + H{sup +} dissociative channel. On the other hand, we show that the experimental observation of the importance of the electronic states with n>3 cannot be well explained theoretically, especially for cold (v=0) ions. We find a good agreement with the experiment on the relative contribution of the {Sigma} and {Pi} states to the cross section for the He{sup +} + H channel, but only a qualitative one for the He + H{sup +} channel. We discuss the factors that could explain the remaining discrepancies between theory and experiment.

  7. Toward black-box-type full- and reduced-dimensional variational (ro)vibrational computations

    NASA Astrophysics Data System (ADS)

    Mátyus, Edit; Czakó, Gábor; Császár, Attila G.

    2009-04-01

    A black-box-type algorithm is presented for the variational computation of energy levels and wave functions using a (ro)vibrational Hamiltonian expressed in an arbitrarily chosen body-fixed frame and in any set of internal coordinates of full or reduced vibrational dimensionality. To make the required numerical work feasible, matrix representation of the operators is constructed using a discrete variable representation (DVR). The favorable properties of DVR are exploited in the straightforward and numerically exact inclusion of any representation of the potential and the kinetic energy including the G matrix and the extrapotential term. In this algorithm there is no need for an a priori analytic derivation of the kinetic energy operator, as all of its matrix elements at each grid point are computed numerically either in a full- or a reduced-dimensional model. Due to the simple and straightforward definition of reduced-dimensional models within this approach, a fully anharmonic variational treatment of large, otherwise intractable molecular systems becomes available. In the computer code based on the above algorithm, there is no inherent limitation for the maximally coupled number of vibrational degrees of freedom. However, in practice current personal computers allow the treatment of about nine fully coupled vibrational dimensions. Computation of vibrational band origins of full and reduced dimensions showing the advantages and limitations of the algorithm and the related computer code are presented for the water, ammonia, and methane molecules.

  8. Rovibrational matrix elements of the quadrupole moment of N2 in a solid parahydrogen matrix

    NASA Astrophysics Data System (ADS)

    Mishra, Adya P.; Balasubramanian, T. K.

    2008-11-01

    The present work pertains to the study of the rotational dynamics of N2 molecules solvated in a matrix of solid para-H2. It is shown that the mixing of the rotational states due to the anisotropic part of the N2-H2 pair potential in the solid gives rise to an additional 5.4% contribution to the intensity of quadrupole-induced double transitions involving N2-H2 pair. Hence the recently reported quadrupole moment matrix element of N2 in a solid para-H2 crystal [A. P. Mishra and T. K. Balasubramanian, J. Chem. Phys. 125, 124507 (2006)], which was deduced from a comparison of the theoretical intensity (with rotational mixing of states neglected) with the measured value is larger by ˜2.7%. The ground electronic state rovibrational matrix elements ⟨v'J'|Q2(r)|vJ⟩ of N2 molecule in a solid parahydrogen matrix for v,v'≤1 and J,J'≤4 have also been computed by taking into account the changes in the intramolecular potential of N2 due to the intermolecular interaction in the matrix. The computed quadrupole moment matrix elements agree well with a few available values (for v =v'=0) deduced from the observed transitions.

  9. Eckart ro-vibrational Hamiltonians via the gateway Hamilton operator: Theory and practice

    NASA Astrophysics Data System (ADS)

    Szalay, Viktor

    2017-03-01

    Recently, a general expression for Eckart-frame Hamilton operators has been obtained by the gateway Hamiltonian method [V. Szalay, J. Chem. Phys. 142, 174107 (2015) and V. Szalay, J. Chem. Phys. 143, 064104 (2015)]. The kinetic energy operator in this general Hamiltonian is nearly identical to that of the Eckart-Watson operator even when curvilinear vibrational coordinates are employed. Its different realizations correspond to different methods of calculating Eckart displacements. There are at least two different methods for calculating such displacements: rotation and projection. In this communication, the application of Eckart Hamiltonian operators constructed by rotation and projection, respectively, is numerically demonstrated in calculating vibrational energy levels. The numerical examples confirm that there is no need for rotation to construct an Eckart ro-vibrational Hamiltonian. The application of the gateway method is advantageous even when rotation is used since it obviates the need for differentiation of the matrix rotating into the Eckart frame. Simple geometrical arguments explain that there are infinitely many different methods for calculating Eckart displacements. The geometrical picture also suggests that a unique Eckart displacement vector may be defined as the shortest (mass-weighted) Eckart displacement vector among Eckart displacement vectors corresponding to configurations related by rotation. Its length, as shown analytically and demonstrated by numerical examples, is equal to or less than that of the Eckart displacement vector one can obtain by rotation to the Eckart frame.

  10. High-level theoretical rovibrational spectroscopy beyond fc-CCSD(T): The C3 molecule.

    PubMed

    Schröder, Benjamin; Sebald, Peter

    2016-01-28

    An accurate local (near-equilibrium) potential energy surface (PES) is reported for the C3 molecule in its electronic ground state (X̃(1)Σg (+)). Special care has been taken in the convergence of the potential relative to high-order correlation effects, core-valence correlation, basis set size, and scalar relativity. Based on the aforementioned PES, several rovibrational states of all (12)C and (13)C substituted isotopologues have been investigated, and spectroscopic parameters based on term energies up to J = 30 have been calculated. Available experimental vibrational term energies are reproduced to better than 1 cm(-1) and rotational constants show relative errors of not more than 0.01%. The equilibrium bond length has been determined in a mixed experimental/theoretical approach to be 1.294 07(10) Å in excellent agreement with the ab initio composite value of 1.293 97 Å. Theoretical band intensities based on a newly developed electric dipole moment function also suggest that the infrared active (1, 1(1), 0)←(0, 0(0), 0) combination band might be observable by high-resolution spectroscopy.

  11. The rovibrational spectrum of hydroxylamine: A combined high resolution experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Luckhaus, D.

    1997-05-01

    This paper reports the rovibrational spectrum of hydroxylamine (NH2OH) recorded by interferometric Fourier transform spectroscopy with a resolution of up to 0.004 cm-1 close to the Doppler limit at room temperature, from 800 cm-1 up to the visible range of the spectrum. Detailed rotational analyses for 32 bands include all nine fundamentals and numerous overtones up to 10 500 cm-1. Approximate absolute band strengths, band centers and vibrational assignments are presented for a total of 72 bands up to the 4ν1 OH stretching overtone. The spectra are interpreted in terms of multidimensional vibrational calculations with potential and dipole surfaces constructed by multidimensional spline interpolation from more than 2×105 ab initioMP2/6-31G** points. The full three dimensional treatment of the torsion-inversion problem reveals well separated time scales for the two processes with a cis potential well supporting localized wave functions for the zero point and fundamental levels. Up to five dimensional normal coordinate models are employed for the analysis and dynamic interpretation of the complete vibrational spectrum up to 21 000 cm-1. Good quantitative agreement between observed spectra and results from ab initio calculations is obtained with a simple harmonic scaling procedure without any further empirical refinement. The comparison of various coupling schemes reveals an efficient path for the coupling between the OH and NH2 manifolds mediated through the OH bending mode. The implications for the effective homogeneous broadening at high energies are discussed.

  12. Toward black-box-type full- and reduced-dimensional variational (ro)vibrational computations.

    PubMed

    Mátyus, Edit; Czakó, Gábor; Császár, Attila G

    2009-04-07

    A black-box-type algorithm is presented for the variational computation of energy levels and wave functions using a (ro)vibrational Hamiltonian expressed in an arbitrarily chosen body-fixed frame and in any set of internal coordinates of full or reduced vibrational dimensionality. To make the required numerical work feasible, matrix representation of the operators is constructed using a discrete variable representation (DVR). The favorable properties of DVR are exploited in the straightforward and numerically exact inclusion of any representation of the potential and the kinetic energy including the G matrix and the extrapotential term. In this algorithm there is no need for an a priori analytic derivation of the kinetic energy operator, as all of its matrix elements at each grid point are computed numerically either in a full- or a reduced-dimensional model. Due to the simple and straightforward definition of reduced-dimensional models within this approach, a fully anharmonic variational treatment of large, otherwise intractable molecular systems becomes available. In the computer code based on the above algorithm, there is no inherent limitation for the maximally coupled number of vibrational degrees of freedom. However, in practice current personal computers allow the treatment of about nine fully coupled vibrational dimensions. Computation of vibrational band origins of full and reduced dimensions showing the advantages and limitations of the algorithm and the related computer code are presented for the water, ammonia, and methane molecules.

  13. A FFT Method for the Quasiclassical Selection of Initial Ro-Vibrational States of Triatomic Molecules

    NASA Technical Reports Server (NTRS)

    Eaker, Charles W.; Schwenke, David W.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    This paper describes the use of an exact fast Fourier transform (FFT) method to prepare specified vibrational-rotational states of triatomic molecules. The method determines the Fourier coefficients needed to describe the coordinates and momenta of a vibrating-rotating triatomic molecule. Once the Fourier coefficients of a particular state are determined, it is possible to easily generate as many random sets of initial cartesian coordinates and momenta as desired. All the members of each set will correspond to the particular vibrational-rotational state selected. For example, in the case of the ground vibrational state of a non-rotating water molecule, the calculated actions of 100 sets of initial conditions produced actions within 0.001 h(bar) of the specified quantization values and energies within 5 cm(sup -1) of the semiclassical eigenvalue. The numerical procedure is straightforward for states in which all the fundamental frequencies are independent. However for states for which the fundamental frequencies become commensurate (resonance states), there are additional complications. In these cases it is necessary to determine a new set of "fundamental" frequencies and to modify the quantization conditions. Once these adjustments are made, good results are obtained for resonance states. The major problems are in labelling the large number of Fourier coefficients and the presence of regions of chaotic motion. Results are presented for the vibrational states of H2O and HCN and the ro-vibrational states of H2O.

  14. A Study of Ro-vibrational OH Emission from Herbig Ae/Be Stars

    NASA Astrophysics Data System (ADS)

    Brittain, Sean D.; Najita, Joan R.; Carr, John S.; Ádámkovics, Máté; Reynolds, Nickalas

    2016-10-01

    We present a study of ro-vibrational OH and CO emission from 21 disks around Herbig Ae/Be stars. We find that the OH and CO luminosities are proportional over a wide range of stellar ultraviolet luminosities. The OH and CO line profiles are also similar, indicating that they arise from roughly the same radial region of the disk. The CO and OH emission are both correlated with the far-ultraviolet luminosity of the stars, while the polycyclic aromatic hydrocarbon (PAH) luminosity is correlated with the longer wavelength ultraviolet luminosity of the stars. Although disk flaring affects the PAH luminosity, it is not a factor in the luminosity of the OH and CO emission. These properties are consistent with models of UV-irradiated disk atmospheres. We also find that the transition disks in our sample, which have large optically thin inner regions, have lower OH and CO luminosities than non-transition disk sources with similar ultraviolet luminosities. This result, while tentative given the small sample size, is consistent with the interpretation that transition disks lack a gaseous disk close to the star.

  15. Merged-beam measurements of absolute cross sections for electron-impact excitation of S{sup 4+} (3s{sup 2} {sup 1}S{yields}3s3p {sup 1}P) and S{sup 5+} (3s {sup 2}S{yields}3p {sup 2}P)

    SciTech Connect

    Wallbank, B.; Bannister, M. E.; Krause, H. F.; Chung, Y.-S.; Smith, A. C. H.; Djuric, N.; Dunn, G. H.

    2007-05-15

    Absolute cross sections for electron-impact excitation of the dipole-allowed transitions S{sup 4+} (3s{sup 2} {sup 1}S{yields}3s3p {sup 1}P) and S{sup 5+} (3s {sup 2}S{yields}3p {sup 2}P) were measured near threshold using the merged electron-ion beams energy-loss technique. Although the magnitudes of the measured cross sections are in reasonable agreement with available theoretical data, the experimental data indicate that the contributions of dielectronic resonances in the near-threshold region are underestimated by these calculations.

  16. Influence of the Reactants Rotational Excitation on the H + D2(v = 0, j) Reactivity.

    PubMed

    Aldegunde, J; Jambrina, P G; González-Sanchez, L; Herrero, V J; Aoiz, F J

    2015-12-17

    We have analyzed the influence of the rotational excitation on the H + D2(v = 0, j) reaction through quantum mechanical (QM) and quasiclassical trajectories (QCT) calculations at a wide range of total energies. The agreement between both types of calculations is excellent. We have found that the rotational excitation largely increases the reactivity at large values of the total energy. Such an increase cannot be attributed to a stereodynamical effect but to the existence of recrossing trajectories that become reactive as the target molecule gets rotationally excited. At low total energies, however, recrossing is not significant and the reactivity evolution is dominated by changes in the collision energy; the reactivity decreases with the collision energy as it shrinks the acceptance cone. When state-to-state results are considered, rotational excitation leads to cold product's rovibrational distributions, so that most of the energy is released as recoil energy.

  17. Influence of the Reactants Rotational Excitation on the H+D2(v=0, j) Reactivity

    PubMed Central

    Aldegunde, J; Jambrina, PG; González-Sanchez, L; Herrero, VJ; Aoiz, FJ

    2016-01-01

    We have analyzed the influence of the rotational excitation on the H+D2(υ=0, j) reaction through quantum mechanical (QM) and quasiclassical trajectories (QCT) calculations at a wide range of total energies. The agreement between both types of calculations is excellent. We have found that the rotational excitation largely increases the reactivity at large values of the total energy. Such increase cannot be attributed to a stereodynamical effect but to the existence of recrossing trajectories that become reactive as the target molecule gets rotationally excited. At low total energies, however, recrossing is not significant and the reactivity evolution is dominated by changes in the collision energy; the reactivity decreases with the collision energy as it shrinks the acceptance cone. When state-to-state results are considered, rotational excitation leads to cold product’s rovibrational distributions, so that most of the energy is released as recoil energy. PMID:26305719

  18. High-Resolution Rovibrational Spectroscopy of Jet-Cooled Phenyl Radical: The ν19 Out-of-Phase Symmetric CH Stretch

    NASA Astrophysics Data System (ADS)

    Buckingham, Grant T.; Chang, Chih-Hsuan; Nesbitt, David J.

    2013-10-01

    Phenyl radical has been studied via sub-Doppler infrared spectroscopy in a slit supersonic discharge expansion source, with assignments for the highest frequency b2 out-of-phase C-H symmetric stretch vibration (-19) unambiguously confirmed by ≤6 MHz (0.0002 cm-1) agreement with microwave ground state combination differences of McMahon et al. [Astrophys. J. 2003, 590, L61-64]. Least squares analysis of over 100 resolved rovibrational peaks in the sub-Doppler spectrum to a Watson Hamiltonian yields precision excited-state rotational constants and a vibrational band origin (-0 = 3071.8915(4) cm-1) consistent with a surprisingly small red-shift (0.9 cm-1) with respect to Ar matrix isolation studies of Ellison and co-workers [J. Am. Chem. Soc. 2001, 123, 1977]. Nuclear spin weights and inertial defects confirm the vibrationally averaged planarity and 2A1 rovibronic symmetry of phenyl radical, with analysis of the rotational constants consistent with a modest C2v distortion of the carbon backbone frame due to partial sp rehybridization of the σ C radical-center. Most importantly, despite the number of atoms (N = 11) and vibrational modes (3N - 6 = 27), phenyl radical exhibits a remarkably clean jet cooled high-resolution IR spectrum that shows no evidence of intramolecular vibrational relaxation (IVR) phenomena such as local or nonlocal perturbations due to strongly coupled nearby dark states. This provides strong support for the feasibility of high-resolution infrared spectroscopy in other aromatic hydrocarbon radical systems.

  19. High-resolution rovibrational spectroscopy of jet-cooled phenyl radical: the ν19 out-of-phase symmetric CH stretch.

    PubMed

    Buckingham, Grant T; Chang, Chih-Hsuan; Nesbitt, David J

    2013-10-03

    Phenyl radical has been studied via sub-Doppler infrared spectroscopy in a slit supersonic discharge expansion source, with assignments for the highest frequency b2 out-of-phase C-H symmetric stretch vibration (ν19) unambiguously confirmed by ≤6 MHz (0.0002 cm(-1)) agreement with microwave ground state combination differences of McMahon et al. [Astrophys. J. 2003, 590, L61-64]. Least squares analysis of over 100 resolved rovibrational peaks in the sub-Doppler spectrum to a Watson Hamiltonian yields precision excited-state rotational constants and a vibrational band origin (ν0 = 3071.8915(4) cm(-1)) consistent with a surprisingly small red-shift (0.9 cm(-1)) with respect to Ar matrix isolation studies of Ellison and co-workers [J. Am. Chem. Soc. 2001, 123, 1977]. Nuclear spin weights and inertial defects confirm the vibrationally averaged planarity and (2)A1 rovibronic symmetry of phenyl radical, with analysis of the rotational constants consistent with a modest C2v distortion of the carbon backbone frame due to partial sp rehybridization of the σ C radical-center. Most importantly, despite the number of atoms (N = 11) and vibrational modes (3N - 6 = 27), phenyl radical exhibits a remarkably clean jet cooled high-resolution IR spectrum that shows no evidence of intramolecular vibrational relaxation (IVR) phenomena such as local or nonlocal perturbations due to strongly coupled nearby dark states. This provides strong support for the feasibility of high-resolution infrared spectroscopy in other aromatic hydrocarbon radical systems.

  20. ON THE ASYMMETRY OF THE OH RO-VIBRATIONAL LINES IN HD 100546

    SciTech Connect

    Fedele, D.; Bruderer, S.; Van den Ancker, M. E.; Pascucci, I. E-mail: mvandena@eso.org

    2015-02-10

    We present multi-epoch high-spectral resolution observations with VLT/CRIRES of the OH doublet {sup 2}Π{sub 3/2} P4.5 (1+, 1–) (2.934 μm) toward the protoplanetary disk around HD 100546. The OH doublet is detected at all epochs and is spectrally resolved while nearby H{sub 2}O lines remain undetected. The OH line velocity profile is different in the three data sets: in the first epoch (2012 April, P.A. = 26°) the OH lines are symmetric and line broadening is consistent with the gas being in Keplerian rotation around the star. No OH emission is detected within a radius of 8-11 AU from the star: the line emitting region is similar in size and extent to that of the CO ro-vibrational lines. In the other two epochs (2013 March and 2014 April, P.A. = 90° and 10°, respectively) the OH lines appear asymmetric and fainter compared to 2012 April. We investigate the origin of these line asymmetries which were taken by previous authors as evidence for tidal interaction between a (unseen) massive planet and the disk. We show that the observed asymmetries can be fully explained by a misalignment of the slit of the order of 0.''04-0.''20 with respect to the stellar position. The disk is spatially resolved and the slit misalignment is likely caused by the extended dust emission which is brighter than the stellar photosphere at near-infrared wavelengths which is the wavelength used for the pointing. This can cause the photo-center of HD 100546 to be misaligned with the stellar position at near-infrared wavelengths.

  1. Optical controling dynamic and fluctuation processes in ensemble of neurons at pulsed electrical excitation ex vivo

    NASA Astrophysics Data System (ADS)

    Akchurin, Garif G.; Seliverstov, George A.; Akchurin, Alexander G.; Akchurin, George G.

    2004-05-01

    Dynamic response of the somatic frog nerve on electrical pulsed excitation was investigated ex vivo. Strong fluctuation of consequence compound action potential in ensemble of neurons near-threshold was discovered. The nonlinear response of the Hodgkin-Huxley model neurons with external electrical pulsed was investigated and numeral results correlation with experiments. Complex dynamic of compound action potential was discovered when on-line time of stimulatory electrical pulses comparable with nerve refractory period. New techniques research nonlinear behavior using photodynamic reactions or UV-A radiation at somatic frog nerve was approved. This nonlinear dynamic regime was controlling laser induced inactivation of processes in membrane of nerve.

  2. Rovibrational Levels and Inelastic Scattering of the H_2O-Ar Cluster in Full and Reduced Dimensionality

    NASA Astrophysics Data System (ADS)

    Ndengue, Steve Alexandre; Majumder, Moumita; Dawes, Richard; Gatti, Fabien; Meyer, Hans-Dieter

    2016-06-01

    The Water-Argon cluster is an important system of fundamental and practical interest. It is for example known to be one of the simplest systems capable of manifesting "hydrophobic interactions" and as such is an ideal candidate for the study of those interactions. On the fundamental level, it is a model system for the description of the intermolecular potential, rovibrational states and inelastic scattering of an atom and an asymmetric top van der Waal complex and thus may serve as a test to perform similar work on other systems. Additionally, the description of the H_2O-Ar intermolecular interaction is an important initial step to a deeper understanding of the static and dynamical properties of condensed phases such H_2O doped in large (Ar)_N clusters. We investigate in this work the H_2O-Ar cluster on a global potential energy surface recently generated. We thus compute the rovibrational energy levels of the cluster in the rigid rotor approximation and in full dimensionality using the MCTDH improved relaxation method and compare our results with available experimental measurements and previous calculations. Then, we present inelastic scattering cross-sections of H_2O+Ar collisions obtained in the rigid rotor approximation using time-independent method and time-dependent method, and compare where available results with previous calculations. Finally, we will discuss the extension of the scattering calculations to the full dimensional case and the prospect of studying rovibrational relaxation within accurate time-dependent quantum calculations on similar systems or clusters.

  3. Rovibrational spectroscopic constants of the interaction between ammonia and metallo-phthalocyanines: a theoretical protocol for ammonia sensor design.

    PubMed

    Baggio, Alan R; Machado, Daniel F S; Carvalho-Silva, Valter H; Paterno, Leonardo G; de Oliveira, Heibbe Cristhian B

    2017-05-03

    In the present contribution, we develop an adapted theoretical approach based on DFT calculations (B3LYP functional) and solution of the nuclear Schrödinger equation by using the Discrete Variable Representation method to model the interaction of ammonia with metallo-phthalocyanines (MPcs, where M = Fe(2+), Co(2+), Ni(2+), Cu(2+) or Zn(2+)). This approach is intended to be a general protocol for the rational design of chemical sensors. The as-obtained binding energy curves, obtained from ab initio points, permitted us to calculate rovibrational energies and spectroscopic constants, as well as to establish the relative population of rovibrational states in different types of MPc-NH3 thermodynamic systems. Simulated binding energy curves show that the binding energy in MPc-NH3 systems is dependent on the type of M central ion, decreasing in the order FePc > ZnPc > CoPc > CuPc > NiPc, with values spanning from -170 to -16 kJ mol(-1). Also, MPc-NH3 systems have at least 16 rovibrational levels, which confirms that they are all bound systems (chemically or physically). Despite that, only the interaction between ammonia and FePc, CoPc or ZnPc is spontaneous within the studied temperature range (200-700 K). NiPc and CuPc show a change between spontaneous and non-spontaneous behaviours at ∼400 K and ∼500 K, respectively. Less bound systems should more efficiently guarantee the sensors' signal reset, while they are also less specific than sensors built with medium to strongly bound systems. Moreover, the intermediate energy and spontaneous binding of ammonia to NiPc and CuPc at operation temperatures, as determined with our theoretical approach, suggests that these MPcs are most promising for ammonia sensors.

  4. Study of the rovibrational intensities of tetrahedral molecules and prediction of the pentad poliade of 12CD4

    NASA Astrophysics Data System (ADS)

    Kaarour, A.; Ouardi, O.; Meskine, M.

    2015-03-01

    The use of tensor models adapted to tetrahedral molecules such CH4, SiH4, GeH4... that use mathematical tools (group theory, irreducible tensor operators) and the characteristics of symmetrical molecules, gives good results. Starting from an experimental spectrum, we can calculate some parameters of the Hamiltonian and consequently the energy levels. Once the line positions are determined, we calculate the parameters of the dipole moment of these molecules and consequently the rovibrational intensities. Both software STDS and SPVIEW, we determined the parameters of the Hamiltonian and those of the dipole moment.

  5. Differential excitation spectroscopy for detection of chemical threats: DMMP and thiodiglycol

    NASA Astrophysics Data System (ADS)

    Hunter, Boyd V.; Cox, Jason M.; Miller, Michael A.; Harrison, Paul; Walters, William P.

    2015-05-01

    Differential Excitation Spectroscopy (DES) is a new pump-probe detection technique (patent-pending) which characterizes molecules based on a multi-dimensional parameterization of the rovibrational excited state structure, pump and probe interrogation frequencies, as well as the lifetimes of the excited states. Under appropriate conditions, significant modulation of the ground state can result. DES results provide a unique, simple mechanism to probe various molecules. In addition, the DES multi-dimensional parameterization provides an identification signature that is highly unique and has demonstrated high levels of immunity from interferents, providing significant practical value for highspecificity material identification. Dimethyl methylphosphonate (DMMP) is used as a simulant for G series nerve agents and thiodiglycol as a simulant for sulfur mustard (HD). Ab initio calculations were performed on DMMP for various rovibrational states up to J' ≤ 3 and validated experimentally, demonstrating good agreement between theory and experiment and the very specific responses generated. Thiodiglycol was investigated empirically. Optimal detection parameters were determined and mixtures of the two materials were used to demonstrate the immunity of the DES technique to interference from other materials, even those whose IR spectra show significant overlap.

  6. Excited Delirium

    PubMed Central

    Takeuchi, Asia; Ahern, Terence L.; Henderson, Sean O.

    2011-01-01

    Excited (or agitated) delirium is characterized by agitation, aggression, acute distress and sudden death, often in the pre-hospital care setting. It is typically associated with the use of drugs that alter dopamine processing, hyperthermia, and, most notably, sometimes with death of the affected person in the custody of law enforcement. Subjects typically die from cardiopulmonary arrest, although the cause is debated. Unfortunately an adequate treatment plan has yet to be established, in part due to the fact that most patients die before hospital arrival. While there is still much to be discovered about the pathophysiology and treatment, it is hoped that this extensive review will provide both police and medical personnel with the information necessary to recognize and respond appropriately to excited delirium. PMID:21691475

  7. Quantum solvent states and rovibrational spectra of small doped 3He clusters through the full-configuration-interaction nuclear orbital approach: The (3He)N-Cl2(X) case (N<=4)

    NASA Astrophysics Data System (ADS)

    de Lara-Castells, María Pilar; Aguirre, Néstor F.; Villarreal, Pablo; Barrio, Gerardo Delgado; Mitrushchenkov, Alexander O.

    2010-05-01

    A full-configuration-interaction nuclear orbital treatment has been recently developed as a benchmark quantum-chemistry-like method to study small doped H3e clusters [M. P. de Lara-Castells et al., J. Chem. Phys. 125, 221101 (2006)]. Our objective in this paper is to extend our previous study on (H3e)N-Cl2(B) clusters, using an enhanced implementation that allows employing very large one-particle basis sets [M. P. de Lara-Castells et al., J. Chem. Phys. 131, 194101 (2009)], and apply the method to the (H3e)N-Cl2(X) case, using both a semiempirical T-shaped and an ab initio He-dopant potential with minima at both T-shaped and linear conformations. Calculations of the ground and low-lying excited solvent states stress the key role played by the anisotropy of the He-dopant interaction in determining the global energies and the structuring of the H3e atoms around the dopant. Whereas H3e atoms are localized in a broad belt around the molecular axis in ground-state N-sized complexes with N =1-3, irrespective of using the T-shaped or the ab initio He-dopant potential function, the dopant species becomes fully coated by just four H3e atoms when the He-dopant potential also has a minimum at linear configurations. However, excited solvent states with a central ring-type clustering of the host molecule are found to be very close in energy with the ground state by using the ab initio potential function. A microscopic analysis of this behavior is provided. Additional simulations of the molecular rovibrational Raman spectra, also including excited solvent states, provide further insights into the importance of proper modeling the anisotropy of the He-dopant interaction in these weakly bound systems and of taking into account the low-lying excitations.

  8. Voiced Excitations

    DTIC Science & Technology

    2004-12-01

    for purposes of vocoding in high noise environments: Task 1: Estimation of voiced excitation functions using skin surface vibration...High Noise Environments. The work on “ Voiced Excitations” shows that the surface vibrations of neck skin, during voicing , carry a great deal of...5 in this report). For field use, it may be better to obtain data from another location on the neck or face. A pressure function of voiced speech is

  9. Excited baryons

    SciTech Connect

    Mukhopadhyay, N.C.

    1986-01-01

    The status of the theory of the low-energy approach to hadron structure is reviewed briefly by surveying a few relevant models. A few examples of tests needed to sort out the predictions of different models pertaining to the quark-gluon structure of hadrons are discussed, and given the resulting physics objectives, a few experimental options for excited baryon research at CFBAF are suggested. (LEW)

  10. Communication: Ro-vibrational control of chemical reactivity in H+CH₄→ H₂+CH₃: full-dimensional quantum dynamics calculations and a sudden model.

    PubMed

    Welsch, Ralph; Manthe, Uwe

    2014-08-07

    The mode-selective chemistry of the title reaction is studied by full-dimensional quantum dynamics simulation on an accurate ab initio potential energy surface for vanishing total angular momentum. Using a rigorous transition state based approach and multi-configurational time-dependent Hartree wave packet propagation, initial state-selected reaction probabilities for many ro-vibrational states of methane are calculated. The theoretical results are compared with experimental trends seen in reactions of methane. An intuitive interpretation of the ro-vibrational control of the chemical reactivity provided by a sudden model based on the quantum transition state concept is discussed.

  11. The molecular and electronic states of 1,2,4,5-tetrazine studied by VUV absorption, near-threshold electron energy-loss spectroscopy and ab initio multi-reference configuration interaction studies

    NASA Astrophysics Data System (ADS)

    Palmer, Michael H.; McNab, Hamish; Reed, David; Pollacchi, Anne; Walker, Isobel C.; Guest, Martyn F.; Siggel, Michele R. F.

    1997-01-01

    The VUV electronic absorption spectrum of 1,2,4,5-tetrazine has been re-investigated, and together with electron energy-loss spectra has led to identification of a number of new excited states. The valence and Rydberg excited states have been studied by multi-reference multi-root configuration interaction studies using MRDCI techniques. Initial studies with the RPA and TDA methods gave almost identical results for the excitation energies, but there is a substantial energy-lowering in the MRDCI calculations, which improves agreement with experiment substantially; these differences are a result of the double, triple and quadruple excited reference configurations included in the reference set of the latter method. The 1ππ ∗ excitations are calculated rather higher than experiment, except for the lowest-lying (weak) 1B 2u state at 5.0 eV. The calculated order for the next three ππ ∗ states is 1B 1u (weak) followed by 1B 2u (strong) and 1B 1u (strong), the last two bands being responsible for the dominant absorption near 7.5 and 8.5 eV. All of this group of four bands involve excitations from the pair of MOs 1b 2g and 1b 1g into the 1a u∗ and 4b 3u∗ VMOs. The sequence of nπ ∗ stakes are in a similar order to the ππ ∗ excitations, with respect to the upper state, and the two lowest singlet states, 1B 3u and 1A u are reasonably well determined. The triplet states follow a similar order to the singlets, and again the dominance of the effect of the two lowest VMOs is demonstrated, but considerable differences between the weighting of leading configurations occurs between singlet and triplet manifolds. The non-diagonal TDA method has been used to reconsider the UV-photoelectron spectrum. The ionisation potentials for tetrazine are reinterpreted with the first three bands being regrouped into 1, 2, 2 ionisations respectively. The ground state properties of tetrazine suggest that the NQR spectrum will show a principal axis 14N quadrupole coupling constant

  12. Electron-impact excitation of multicharged ions: Merged beams experiments

    SciTech Connect

    Bannister, M.E.; Chung, Y.; Djuric, N.; Dunn, G.H.; Woitke, O.; Smith, A.C.; Wallbank, B.

    1999-06-01

    Electron-impact excitation cross sections for several multicharged ions have been measured near threshold using the merged electron-ion beams energy loss (MEIBEL) technique. This technique allows the investigation of optically-allowed and forbidden transitions with sufficient energy resolution, typically about 0.2 eV, to resolve resonance structures in the cross sections. Results from the JILA/ORNL MEIBEL experiment on allowed transitions in several multicharged ions demonstrate the ability of various theoretical methods to predict cross sections in the absence of resonances. Comparisons of R-matrix calculations and measured cross sections for transitions in Mg-like Si{sup 2+} and Ar{sup 6+}, however, indicate that theory must continue to evolve in order to more accurately predict cross sections involving significant contributions from dielectronic resonances and interactions between neighboring resonances. {copyright} {ital 1999 American Institute of Physics.}

  13. HIGH-RESOLUTION NEAR-INFRARED SPECTROSCOPY OF HD 100546. I. ANALYSIS OF ASYMMETRIC RO-VIBRATIONAL OH EMISSION LINES

    SciTech Connect

    Liskowsky, Joseph P.; Brittain, Sean D.; Najita, Joan R.; Carr, John S.; Doppmann, Greg W.; Troutman, Matthew R. E-mail: najita@noao.edu E-mail: gdoppmann@keck.hawaii.edu

    2012-12-01

    We present observations of ro-vibrational OH and CO emission from the Herbig Be star HD 100546. The emission from both molecules arises from the inner region of the disk extending from approximately 13 AU from the central star. The velocity profiles of the OH lines are narrower than the velocity profile of the [O I] {lambda}6300 line, indicating that the OH in the disk is not cospatial with the O I. This suggests that the inner optically thin region of the disk is largely devoid of molecular gas. Unlike the ro-vibrational CO emission lines, the OH lines are highly asymmetric. We show that the average CO and average OH line profiles can be fit with a model of a disk comprised of an eccentric inner wall and a circular outer disk. In this model, the vast majority of the OH flux (75%) originates from the inner wall, while the vast majority of the CO flux (65%) originates on the surface of the disk at radii greater than 13 AU. Eccentric inner disks are predicted by hydrodynamic simulations of circumstellar disks containing an embedded giant planet. We discuss the implications of such a disk geometry in light of models of planet-disk tidal interactions and propose alternative explanations for the origin of the asymmetry.

  14. Computational study of the rovibrational spectra of CO2-C2H2 and CO2-C2D2

    NASA Astrophysics Data System (ADS)

    Donoghue, Geoff; Wang, Xiao-Gang; Dawes, Richard; Carrington, Tucker

    2016-12-01

    An intermolecular potential energy surface and rovibrational transition frequencies are computed for CO2-C2H2. An interpolating moving least squares method is used to fit ab initio points at the explicitly correlated coupled-cluster level. The rovibrational Schrödinger equation is solved with a symmetry-adapted Lanczos algorithm. The computed disrotatory and torsion vibrational levels of both CO2-C2H2 and CO2-C2D2 differ from those obtained by experimentalists by less than 0.5 cm-1. CO2-C2H2 has two equivalent minima with the monomers perpendicular to the inter-monomer axis. In contrast to many other Van der Waals dimers there is no disrotatory path that connects the minima. The tunnelling path follows the torsional coordinate over a high barrier and the splitting is therefore tiny. Using vibrational parent analysis we are able to fit and thus obtain rotational constants and centrifugal distortion constants. Calculated rotational constants differ from their experimental counterparts by less than 0.001 cm-1.

  15. Communication: The ground electronic state of Si2C: Rovibrational level structure, quantum monodromy, and astrophysical implications.

    PubMed

    Reilly, Neil J; Changala, P Bryan; Baraban, Joshua H; Kokkin, Damian L; Stanton, John F; McCarthy, Michael C

    2015-06-21

    We report the gas-phase optical detection of Si2C near 390 nm and the first experimental investigation of the rovibrational structure of its (1)A1 ground electronic state using mass-resolved and fluorescence spectroscopy and variational calculations performed on a high-level ab initio potential. From this joint study, it is possible to assign all observed Ka = 1 vibrational levels up to 3800 cm(-1) with confidence, as well as a number of levels in the Ka = 0, 2,  and 3 manifolds. Dixon-dip plots for the bending coordinate (ν2) allow an experimental determination of a barrier to linearity of 783(48) cm(-1) (2σ), in good agreement with theory (802(9) cm(-1)). The calculated (Ka, ν2) eigenvalue lattice shows an archetypal example of quantum monodromy (absence of a globally valid set of quantum numbers) that is reflected by the experimentally observed rovibrational levels. The present study provides a solid foundation for infrared and optical surveys of Si2C in astronomical objects, particularly in the photosphere of N- and J-type carbon stars where the isovalent SiC2 molecule is known to be abundant.

  16. Improved ground state and ν12 = 1 state rovibrational constants for ethylene-13C2 (13C2H4)

    NASA Astrophysics Data System (ADS)

    Gabona, M. G.; Tan, T. L.

    2014-05-01

    The Fourier transform infrared (FTIR) absorption spectrum of the ν12 fundamental band of ethylene-13C2 (13C2H4) was recorded in the frequency range of 1350-1550 cm-1 with unapodized resolution of 0.0063 cm-1. Improved upper state (ν12 = 1) rovibrational constants consisting of three rotational, five quartic and five sextic constants were derived by assigning and fitting 1731 infrared transitions using Watson's A-reduced Hamiltonian in the Ir representation. The root-mean-square deviation of the fit was 0.00030 cm-1. More higher-order upper state (ν12 = 1) constant were derived in the present analysis than previously reported. Improved ground state rovibrational constants were also determined from the fit of 1104 ground state combination differences (GSCD) with a root-mean-square deviation of 0.00029 cm-1. The A-type ν12 band centered at 1436.65409 ± 0.00002 cm-1 has a calculated inertial defect Δ12 is 0.242896 ± 0.000007 μÅ2. No indications of perturbation were found in the analysis of the band.

  17. ASPIN: An all spin scattering code for atom molecule rovibrationally inelastic cross sections

    NASA Astrophysics Data System (ADS)

    López-Durán, D.; Bodo, E.; Gianturco, F. A.

    2008-12-01

    We present in this work a new computational code for the quantum calculation of integral cross sections for atom-molecule (linear) scattering processes. The atom is taken to be structureless while the molecule can be in its singlet, doublet, or triplet spin states and can be treated as either a rigid rotor or a rovibrational target. All the relevant state-to-state integral cross sections, and their sums over final states, can be calculated with the present code, for which we also describe in detail the various component routines. Program summaryProgram title: ASPIN Catalogue identifier: AEBO_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEBO_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 99 596 No. of bytes in distributed program, including test data, etc.: 1 267 615 Distribution format: tar.gz Programming language: Fortran/MPI Computer: AMD OPTERON COMPUTING SYSTEMS, model TYAN GX28 (B2882) Operating system: SuSE LINUX Professional 9 RAM: 128 GB Classification: 2.6 External routines: LAPACK/BLAS Nature of problem: Scattering of a diatomic molecule in its Σ1, Σ2, or Σ3 spin states with an atom in its S1 state. Partial and integral cross sections. Solution method: The coupled channel equations that describe the scattering process are solved through the propagation of the reactance K matrix employing a modification of the Variable Phase Method [1-3]. Restrictions: Depending on the vib-rotational base used the problem may or may not fit into available RAM memory because all the runtime relevant quantities are stored on RAM memory instead of on disk. Additional comments: Both serial and parallel implementations of the program are provided. The CPC Librarian was not able to successfully run the parallel version. Running time: For simple and converged

  18. Fourfold Clusters of Rovibrational Energy Levels in the Fundamental Vibrational States of H 2Se

    NASA Astrophysics Data System (ADS)

    Kozin, I. N.; Jensen, P.

    1993-09-01

    We report here a calculation of the rotation-vibration energies in the ν1, ν2, ν3, and 2ν2 vibrational states of H280Se using the MORBID (Morse oscillator rigid bender internal dynamics) Hamiltonian and computer program [P. Jensen, J. Mol. Spectrosc.128, 478-501 (1988); J. Chem. Soc. Faraday Trans. 284, 1315-1340 (1988)]. As input data for the calculation, we employ a potential energy surface recently determined from experimental data by means of the MORBID approach [P. Jensen and I. N. Kozin. J. Mol. Spectrosc., in press.]. For all of the vibrational states considered. the calculation shows that as J increases, fourfold rovibrational energy clusters are formed. This effect has already been experimentally verified for the vibrational ground state and its origin was shown to lie in the centrifugal distortion of the molecule [I. N. Kozin, S. P. Belov, O. L. Polyansky, and M. Yu. Tretyakov, J. Mol. Spectrosc.152, 13-28 (1992); I. N. Kozin, O. L. Polyansky, S. I. Pripolzin, and V. L. Vaks, J. Mol. Spectrosc.156, 504-506 (l992); I. N. Kozin, S. Klee, P. Jensen, O. L. Polyansky, and I. M. Pavlichenkov, J. Mol. Spectrosc.,158, 409-422 (1993)]. We find here that the cluster formation in the ν2 and 2ν2 vibrational states is completely analogous to that in the vibrational ground state. For the ν1/ν3 interacting vibrational states, however, we predict a new type of fourfold clusters. We can describe their formation as a coalescence (with increasing J) of two energy doublets, where one doublet belongs to the ν1 vibrational state and the other one to the ν3 vibrational state, An interpretation of the "new" cluster eigenstates is given, and the origins of the cluster formation are discussed in terms of semiclassical theory. The semiclassical analysis shows that the new clusters are caused essentially bx the rotational interactions between the ν1 and the ν3 states. The predicted term values from the present work are found to be in good agreement with experimental

  19. The cyclopropene radical cation: Rovibrational level structure at low energies from high-resolution photoelectron spectra

    SciTech Connect

    Vasilatou, K.; Michaud, J. M.; Baykusheva, D.; Grassi, G.; Merkt, F.

    2014-08-14

    The cyclopropene radical cation (c-C{sub 3}H{sub 4}{sup +}) is an important but poorly characterized three-membered-ring hydrocarbon. We report on a measurement of the high-resolution photoelectron and photoionization spectra of cyclopropene and several deuterated isotopomers, from which we have determined the rovibrational energy level structure of the X{sup ~+} {sup 2}B{sub 2} ground electronic state of c-C{sub 3}H{sub 4}{sup +} at low energies for the first time. The synthesis of the partially deuterated isotopomers always resulted in mixtures of several isotopomers, differing in their number of D atoms and in the location of these atoms, so that the photoelectron spectra of deuterated samples are superpositions of the spectra of several isotopomers. The rotationally resolved spectra indicate a C{sub 2v}-symmetric R{sub 0} structure for the ground electronic state of c-C{sub 3}H{sub 4}{sup +}. Two vibrational modes of c-C{sub 3}H{sub 4}{sup +} are found to have vibrational wave numbers below 300 cm{sup −1}, which is surprising for such a small cyclic hydrocarbon. The analysis of the isotopic shifts of the vibrational levels enabled the assignment of the lowest-frequency mode (fundamental wave number of ≈110 cm{sup −1} in c-C{sub 3}H{sub 4}{sup +}) to the CH{sub 2} torsional mode (ν{sub 8}{sup +}, A{sub 2} symmetry) and of the second-lowest-frequency mode (≈210 cm{sup −1} in c-C{sub 3}H{sub 4}{sup +}) to a mode combining a CH out-of-plane with a CH{sub 2} rocking motion (ν{sub 15}{sup +}, B{sub 2} symmetry). The potential energy along the CH{sub 2} torsional coordinate is flat near the equilibrium structure and leads to a pronounced anharmonicity.

  20. Sexual excitement.

    PubMed

    Stoller, R J

    1976-08-01

    Sexual excitement depends on a scenario the person to be aroused has been writing since childhood. The story is an adventure, an autobiography disguised as fiction, in which the hero/heroine hides crucial intrapsychic conflicts, mysteries, screen memories of actual traumatic events and the resolution of these elements into a happy ending, best celebrated by orgasm. The function of the fantasy is to take these painful experiences and convert them to pleasure-triumph. In order to sharpen excitement-the vibration between the fear of original traumas repeating and the hope of a pleasurable conclusion this time-one introduces into the story elements of risk (approximations of the trauma) meant to prevent boredom and safety factors (sub-limnal signals to the storyteller that the risk are not truly dangerous). Sexual fantasy can be studied by means of a person's daydreams (including those chosen in magazines, books, plays, television, movies, and outright pornography), masturbatory behavior, object choice, foreplay, techniques of intercourse, or postcoital behavior.

  1. Four-component relativistic coupled cluster and configuration interaction calculations on the ground and excited states of the RbYb molecule.

    PubMed

    Sørensen, Lasse Kragh; Knecht, Stefan; Fleig, Timo; Marian, Christel M

    2009-11-12

    We present high-level four-component coupled cluster and multireference configuration interaction calculations of potential energy curves, dipole moment, Franck-Condon factors and spectroscopic constants of the newly formed RbYb molecule. From finite-field calculations we obtain an electric dipole moment for RbYb of almost 1 D. In combination with its magnetic dipole moment this makes RbYb an excellent candidate for trapping and for studying dipolar interaction in the ultracold regime. Significant Franck-Condon factors are found between the rovibronic ground state and the lowest rovibrational levels of the first excited 2Sigma1/2+ state but also between a broad range of rovibrational levels of the 2Pi1/2 and 2Pi3/2 states. This allows for several two-step approaches to reach the rovibronic ground state after initial photoassociation.

  2. Rovibrational dynamics of the strontium molecule in the A(1)Σ(u)+, c(3)Π(u), and a(3)Σ(u)+ manifold from state-of-the-art ab initio calculations.

    PubMed

    Skomorowski, Wojciech; Pawłowski, Filip; Koch, Christiane P; Moszynski, Robert

    2012-05-21

    State-of-the-art ab initio techniques have been applied to compute the potential energy curves for the electronic states in the A(1)Σ(u)(+), c(3)Π(u), and a(3)Σ(u)(+) manifold of the strontium dimer, the spin-orbit and nonadiabatic coupling matrix elements between the states in the manifold, and the electric transition dipole moment from the ground X(1)Σ(g)(+) to the nonrelativistic and relativistic states in the A+c+a manifold. The potential energy curves and transition moments were obtained with the linear response (equation of motion) coupled cluster method limited to single, double, and linear triple excitations for the potentials and limited to single and double excitations for the transition moments. The spin-orbit and nonadiabatic coupling matrix elements were computed with the multireference configuration interaction method limited to single and double excitations. Our results for the nonrelativistic and relativistic (spin-orbit coupled) potentials deviate substantially from recent ab initio calculations. The potential energy curve for the spectroscopically active (1)0(u)(+) state is in quantitative agreement with the empirical potential fitted to high-resolution Fourier transform spectra [A. Stein, H. Knöckel, and E. Tiemann, Eur. Phys. J. D 64, 227 (2011)]. The computed ab initio points were fitted to physically sound analytical expressions, and used in converged coupled channel calculations of the rovibrational energy levels in the A+c+a manifold and line strengths for the A(1)Σ(u)(+)←X(1)Σ(g (+) transitions. Positions and lifetimes of quasi-bound Feshbach resonances lying above the (1)S(0) + (3)P(1) dissociation limit were also obtained. Our results reproduce (semi)quantitatively the experimental data observed thus far. Predictions for on-going and future experiments are also reported.

  3. Low Energy Electron Impact Excitation of Water

    NASA Astrophysics Data System (ADS)

    Ralphs, Kevin; Serna, Gabriela; Hargreaves, Leigh R.; Khakoo, Murtadha A.; Winstead, Carl; McKoy, B. Vincent

    2011-10-01

    We present normalized absolute differential and integral cross-section measurements for the low energy electron impact excitation of the lowest dissociative 3B1, 1B1,3A1 and 1A1 states of H2O. The DCS were taken at incident energies of 9 eV, 10 eV, 12 eV, 15 eV and 20 eV and scattering angles of 15° to 130° and normalized to the elastic electron scattering measurements of. The DCS were obtained after a sophisticated unfolding of the electron energy loss spectrum of water using photoabsorption data in the literature as investigated by Thorn et al.. Our measurements extend those of to near-threshold energies. We find both important agreements and differences between our DCS and those of. Comparison to our theory (multi-channel Schwinger) and that of earlier work will also be presented. Funded by an NSF grant # RUI-PHY 0968874.

  4. Positron-impact ionization, positronium formation, and electronic excitation cross sections for diatomic molecules

    SciTech Connect

    Marler, J. P.; Surko, C. M.

    2005-12-15

    Absolute measurements are presented for the positron-impact cross sections for positronium formation, direct ionization, and total ionization of the diatomic molecules N{sub 2}, CO, and O{sub 2}, in the range of energies from threshold to 90 eV. Cross sections for the electronic excitation of the a {sup 1}{pi} and a{sup '} {sup 1}{sigma} state in N{sub 2} and the A {sup 1}{pi} state in CO near threshold are also presented. The experiment uses a cold, trap-based positron beam and the technique of studying positron scattering in a strong magnetic field. In O{sub 2}, a feature previously seen in the total ionization cross section is observed in both the positronium formation and total ionization cross sections. The possible origin of this feature and its relationship to positron-induced dissociation is discussed. In N{sub 2}, the near-threshold electronic excitation cross section is larger than that for positronium formation. This likely explains the relatively high efficiency of this molecule when used for buffer-gas positron trapping.

  5. Automatic Generation of Analytic Equations for Vibrational and Rovibrational Constants from Fourth-Order Vibrational Perturbation Theory

    NASA Astrophysics Data System (ADS)

    Matthews, Devin A.; Gong, Justin Z.; Stanton, John F.

    2014-06-01

    The derivation of analytic expressions for vibrational and rovibrational constants, for example the anharmonicity constants χij and the vibration-rotation interaction constants α^B_r, from second-order vibrational perturbation theory (VPT2) can be accomplished with pen and paper and some practice. However, the corresponding quantities from fourth-order perturbation theory (VPT4) are considerably more complex, with the only known derivations by hand extensively using many layers of complicated intermediates and for rotational quantities requiring specialization to orthorhombic cases or the form of Watson's reduced Hamiltonian. We present an automatic computer program for generating these expressions with full generality based on the adaptation of an existing numerical program based on the sum-over-states representation of the energy to a computer algebra context. The measures taken to produce well-simplified and factored expressions in an efficient manner are discussed, as well as the framework for automatically checking the correctness of the generated equations.

  6. First-principles calculations of rovibrational energies, dipole transition intensities and partition function for ethylene using MULTIMODE.

    PubMed

    Carter, Stuart; Sharma, Amit R; Bowman, Joel M

    2012-10-21

    Large-scale, rovibrational variational calculations are performed for ethylene, using the potential energy surface published by Avila and Carrington [J. Chem. Phys. 135, 064101 (2011)]. Energies for J = 0 are in very good agreement with their benchmark results. Corresponding energies for J = 1 and J = 2 are also given. Calculations with a slightly reduced basis permit energies to J = 40, allowing a reliable determination of the partition function at 296 K. Using a new ab initio dipole moment surface, reported here, the infrared spectra of five dipole-allowed fundamentals are calculated. Both the partition function and infrared spectra are shown to be in excellent agreement with those in the experimental HITRAN database, with the exception of one band, which we believe is partially mis-assigned in HITRAN.

  7. Rovibrational Line Lists for Nine Isotopologues of the CO Molecule in the X 1Σ+ Ground Electronic State

    NASA Astrophysics Data System (ADS)

    Li, Gang; Gordon, Iouli E.; Rothman, Laurence S.; Tan, Yan; Hu, Shui-Ming; Kassi, Samir; Campargue, Alain; Medvedev, Emile S.

    2015-01-01

    Extensive rovibrational line lists were computed for nine isotopologues of the CO molecule, namely, 12C16O, 12C17O, 12C18O, 13C16O, 13C17O, 13C18O, 14C16O, 14C17O, and 14C18O in the ground electronic state with v <= 41, Δv <= 11, and J <= 150. The line intensity and position calculations were carried out using a newly determined piece-wise dipole moment function (DMF) in conjunction with the wavefunctions calculated from an experimentally determined potential energy function from Coxon & Hajigeorgiou. A direct-fit method that simultaneously fits all the reliable experimental rovibrational matrix elements has been used to construct the dipole moment function near equilibrium internuclear distance. In order to extend the amount and quality of input experimental parameters, new Cavity Ring Down Spectroscopy experiments were carried out to enable measurements of the lines in the 4-0 band with low uncertainty as well as the first measurements of lines in the 6-0 band. A new high-level ab initio DMF, derived from a finite field approach has been calculated to cover internuclear distances far from equilibrium. Accurate partition sums have been derived for temperatures up to 9000 K. In addition to air- and self-induced broadening and shift parameters, those induced by CO2 and H2 are now provided for planetary applications. A complete set of broadening and shift parameters was calculated based on sophisticated extrapolation of high-quality measured data. The line lists, which follow HITRAN formalism, are provided as supplementary material.

  8. Fully relativistic rovibrational energies and spectroscopic constants of the lowest X:(1)0(+)g, A':(1)2( u ), A:(1)1 ( u ), B':(1)0(-)u and B:(1)0(+)u states of molecular chlorine.

    PubMed

    Machado, Daniel F S; Silva, Valter H C; Esteves, Cristiano S; Gargano, Ricardo; Macedo, Luiz G M; Mundim, Kleber C; de Oliveira, Heibbe C B

    2012-09-01

    The main goal of this paper is to present the rovibrational energies and spectroscopic constants of the Cl(2) molecular system in the relativistic states [Formula: see text], A':(1)2( u ), A:(1)1( u ), [Formula: see text] and [Formula: see text]. More precisely, we have evaluated the Cl(2) ω ( e ), ω ( e ) x ( e ), ω ( e ) y ( e ), α ( e ), γ ( e ) and B ( e ) rovibrational spectroscopic constants using two different procedures. The first was obtained by combining the rovibrational energies, calculated through solving Schrödinger's nuclear equation and the diatomic rovibrational energy equation. The second was obtained by using the Dunham method. The calculated properties are in good agreement with available experimental data.

  9. Electronic and rovibrational quantum chemical analysis of C3P-: the next interstellar anion?

    NASA Astrophysics Data System (ADS)

    Fortenberry, Ryan C.; Lukemire, Joseph A.

    2015-11-01

    C3P- is analogous to the known interstellar anion C3N- with phosphorus replacing nitrogen in a simple step down the periodic table. In this work, it is shown that C3P- is likely to possess a dipole-bound excited state. It has been hypothesized and observationally supported that dipole-bound excited states are an avenue through which anions could be formed in the interstellar medium. Additionally, C3P- has a valence excited state that may lead to further stabilization of this molecule, and C3P- has a larger dipole moment than neutral C3P (˜6 D versus ˜4 D). As such, C3P- is probably a more detectable astromolecule than even its corresponding neutral radical. Highly accurate quantum chemical quartic force fields are also applied to C3P- and its singly 13C substituted isotopologues in order to provide structures, vibrational frequencies, and spectroscopic constants that may aid in its detection.

  10. Generalized Dalitz plot analysis of the near-threshold pp{yields}ppK{sup +}K{sup -} reaction in view of the K{sup +}K{sup -} final state interaction

    SciTech Connect

    Silarski, M.; Czyzykiewicz, R.; Gil, D.; Jarczyk, L.; Kamys, B.; Smyrski, J.; Zielinski, M.; Zdebik, J.; Moskal, P.; Czerwinski, E.; Klaja, J.; Klaja, P.; Krzemien, W.; Grzonka, D.; Oelert, W.; Ritman, J.; Sefzick, T.; Wolke, M.; Wuestner, P.; Khoukaz, A.

    2009-10-15

    The excitation function for the pp{yields}ppK{sup +}K{sup -} reaction revealed a significant enhancement close to threshold that may plausibly be assigned to the influence of the pK{sup -} and K{sup +}K{sup -} final-state interactions. In an improved reanalysis of COSY-11 data for the pp{yields}ppK{sup +}K{sup -} reaction at excess energies of Q=10 and 28 MeV, including the proton-K{sup -} interaction, the enhancement is confirmed. Invariant mass distributions for the two- and three-particle subsystems allow us to test at low excess energies the ansatz and parameters for the description of the interaction in the ppK{sup +}K{sup -} system as derived from the COSY-ANKE data. Finally, based for the first time on the low-energy K{sup +}K{sup -} invariant mass distributions and the generalized Dalitz plot analysis, we estimate the scattering length for the K{sup +}K{sup -} interaction to be |Re(a{sub K{sup +}}{sub K{sup -}})|=0.5{sub -0.5}{sup +4.0} fm and Im(a{sub K{sup +}}{sub K{sup -}})=3.0{+-}3.0 fm.

  11. Quartic force fields for excited electronic states: rovibronic reference data for the 1 (2)A' and 1 (2)A″ states of the isoformyl radical, HOC.

    PubMed

    Morgan, W James; Fortenberry, Ryan C

    2015-01-25

    Quartic force fields (QFFs) have been shown to be an effective, accurate, and relatively compact means of computing rovibrational spectroscopic data for numerous molecules with numerous applications. However, excited states have been nearly excluded from the this approach since most accurate QFFs are based on the "gold standard" coupled cluster singles, doubles, and perturbative triples [CCSD(T)] method which is not readily extended to excited states. In this work, rovibronic spectroscopic data is provided for the isoformyl radical, a molecule of significance in combustion and astrochemistry, both through the traditional means of variational access to excited states with CCSD(T) and in the novel extension of QFFs routinely to treat electronically excited states through the standard coupled cluster excited state approach, equation of motion (EOM) CCSD. It is shown here that the new EOM-based QFF provides structural parameters and rotational constants that are quite close to those from a related CCSD(T)-based QFF for the 1 (2)A(″) excited state of HOC. The anharmonic vibrational frequency percent differences between the two QFFs are less than 0.4% for the O-H stretch, less than 1.9% for the C-O stretch, and around 3.0% for the bend. Even so, the pure excited state EOM-QFF anharmonic frequencies are still very good abinitio representations that may be applied to systems where electronically excited states are not variationally accessible. Additionally, rovibrational spectroscopic data is provided for the 1 (2)A(') ground state of HOC and for both the ground and excited state of DOC.

  12. Transfer of Rovibrational Energies in Hydrogen Plasma-Carbon Surface Interactions

    DTIC Science & Technology

    2009-01-01

    z position of the c.m. along the surface normal, xcm and, ycm are sampled uni- formly, and~pcm is sampled from a shifted Maxwell–Boltzmann dis...Typical beam energies are 70 eV; this is chosen to be well above the threshold for H2 electronic excitation (&10 eV) so that signal brightness is not...0 at the tube entrance and the accommodation coefficients arot and avib. Wall collisions are as- sumed to be diffuse . The kinetic temperature is

  13. The NaK 1 1,3delta states: theoretical and experimental studies of fine and hyperfine structure of rovibrational levels near the dissociation limit.

    PubMed

    Wilkins, A D; Morgus, L; Hernandez-Guzman, J; Huennekens, J; Hickman, A P

    2005-09-22

    Earlier high-resolution spectroscopic studies of the fine and hyperfine structure of rovibrational levels of the 1 3delta state of NaK have been extended to include high lying rovibrational levels with v < or = 59, of which the highest levels lie within approximately 4 cm(-1) of the dissociation limit. A potential curve is determined using the inverted perturbation approximation method that reproduces these levels to an accuracy of approximately 0.026 cm(-1). For the largest values of v, the outer turning points occur near R approximately 12.7 angstroms, which is sufficiently large to permit the estimation of the C6 coefficient for this state. The fine and hyperfine structure of the 1 3delta rovibrational levels has been fit using the matrix diagonalization method that has been applied to other states of NaK, leading to values of the spin-orbit coupling constant A(v) and the Fermi contact constant b(F). New values determined for v < or = 33 are consistent with values determined by a simpler method and reported earlier. The measured fine and hyperfine structure for v in the range 44 < or = v < or = 49 exhibits anomalous behavior whose origin is believed to be the mixing between the 1 3delta and 1 1delta states. The matrix diagonalization method has been extended to treat this interaction, and the results provide an accurate representation of the complicated patterns that arise. The analysis leads to accurate values for A(v) and b(F) for all values of v < or = 49. For higher v (50 < or = v < or = 59), several rovibrational levels have been assigned, but the pattern of fine and hyperfine structure is difficult to interpret. Some of the observed features may arise from effects not included in the current model.

  14. Modelling non-adiabatic effects in H_3^+: Solution of the rovibrational Schrödinger equation with motion-dependent masses and mass surfaces

    NASA Astrophysics Data System (ADS)

    Mátyus, Edit; Szidarovszky, Tamás; Császár, Attila G.

    2014-10-01

    Introducing different rotational and vibrational masses in the nuclear-motion Hamiltonian is a simple phenomenological way to model rovibrational non-adiabaticity. It is shown on the example of the molecular ion H_3^+, for which a global adiabatic potential energy surface accurate to better than 0.1 cm-1 exists [M. Pavanello, L. Adamowicz, A. Alijah, N. F. Zobov, I. I. Mizus, O. L. Polyansky, J. Tennyson, T. Szidarovszky, A. G. Császár, M. Berg et al., Phys. Rev. Lett. 108, 023002 (2012)], that the motion-dependent mass concept yields much more accurate rovibrational energy levels but, unusually, the results are dependent upon the choice of the embedding of the molecule-fixed frame. Correct degeneracies and an improved agreement with experimental data are obtained if an Eckart embedding corresponding to a reference structure of D3h point-group symmetry is employed. The vibrational mass of the proton in H_3^+ is optimized by minimizing the root-mean-square (rms) deviation between the computed and recent high-accuracy experimental transitions. The best vibrational mass obtained is larger than the nuclear mass of the proton by approximately one third of an electron mass, m^(v)_opt,p=m_nuc,p+0.31224 m_e. This optimized vibrational mass, along with a nuclear rotational mass, reduces the rms deviation of the experimental and computed rovibrational transitions by an order of magnitude. Finally, it is shown that an extension of the algorithm allowing the use of motion-dependent masses can deal with coordinate-dependent mass surfaces in the rovibrational Hamiltonian, as well.

  15. Modelling non-adiabatic effects in H{sub 3}{sup +}: Solution of the rovibrational Schrödinger equation with motion-dependent masses and mass surfaces

    SciTech Connect

    Mátyus, Edit; Szidarovszky, Tamás

    2014-10-21

    Introducing different rotational and vibrational masses in the nuclear-motion Hamiltonian is a simple phenomenological way to model rovibrational non-adiabaticity. It is shown on the example of the molecular ion H{sub 3}{sup +}, for which a global adiabatic potential energy surface accurate to better than 0.1 cm{sup −1} exists [M. Pavanello, L. Adamowicz, A. Alijah, N. F. Zobov, I. I. Mizus, O. L. Polyansky, J. Tennyson, T. Szidarovszky, A. G. Császár, M. Berg et al., Phys. Rev. Lett. 108, 023002 (2012)], that the motion-dependent mass concept yields much more accurate rovibrational energy levels but, unusually, the results are dependent upon the choice of the embedding of the molecule-fixed frame. Correct degeneracies and an improved agreement with experimental data are obtained if an Eckart embedding corresponding to a reference structure of D{sub 3h} point-group symmetry is employed. The vibrational mass of the proton in H{sub 3}{sup +} is optimized by minimizing the root-mean-square (rms) deviation between the computed and recent high-accuracy experimental transitions. The best vibrational mass obtained is larger than the nuclear mass of the proton by approximately one third of an electron mass, m{sub opt,p}{sup (v)}=m{sub nuc,p}+0.31224 m{sub e}. This optimized vibrational mass, along with a nuclear rotational mass, reduces the rms deviation of the experimental and computed rovibrational transitions by an order of magnitude. Finally, it is shown that an extension of the algorithm allowing the use of motion-dependent masses can deal with coordinate-dependent mass surfaces in the rovibrational Hamiltonian, as well.

  16. A rigorous full-dimensional quantum dynamics study of tunneling splitting of rovibrational states of vinyl radical C2H3

    NASA Astrophysics Data System (ADS)

    Yu, Hua-Gen; Song, Hongwei; Yang, Minghui

    2017-06-01

    We report a rigorous quantum mechanical study of the rovibrational energy levels of vinyl radical C2H3. The calculations are carried out using a real two-component multi-layer Lanczos algorithm in a set of orthogonal polyspherical coordinates based on a recently developed accurate ab initio potential energy surface of C2H3. All well converged 158 vibrational bands up to 3200 cm-1 are determined, together with a comparison to previous calculations and experimental results. Results show a remarkable multi-dimensional tunneling effect on the vibrational spectra of the radical. The vibrational tunneling splitting is substantially different from that of previous reduced dimensional calculations. The rotational constants of the fundamental vibrational bands of C2H3 are also given. It was found that the rovibrational states are strongly coupled, especially among those bending vibrational modes. In addition, the perturbative iteration approach of Gruebele has been extended to assign the rovibrational energy levels of C2H3 without the requirement of explicit wavefunctions.

  17. Electronic structure and rovibrational properties of ZnOH in the X̃²A' electronic state: a computational molecular spectroscopy study.

    PubMed

    Hirano, Tsuneo; Andaloussi, Mounir Ben Dahman; Nagashima, Umpei; Jensen, Per

    2014-09-07

    The three-dimensional ground-state potential energy surface of ZnOH has been calculated ab initio at the MR-SDCI+Q_DK3/[QZP ANO-RCC (Zn, O, H)] level of theory and used as basis for a study of the rovibrational properties carried out by means of the program MORBID (Morse Oscillator Rigid Bender Internal Dynamics). The electronic ground state is  (2)A' (correlating with (2)Σ(+) at the linear configuration). The equilibrium structure has r(e)(Zn-O) = 1.8028 Å, r(e)(O-H) = 0.9606 Å, and ∠e(Zn-O-H) = 114.9°. The Zn-O bond is essentially ionic, with appreciable covalency. The bonding character is compared with those of FeOH (quasi-linear) and CsOH (linear). The rovibrationally averaged structural parameters, determined as expectation values over MORBID wavefunctions, are ⟨r(Zn-O)⟩0 = 1.8078 Å, ⟨r(O-H)⟩0 = 0.9778 Å, and ⟨∠(Zn-O-H)⟩0 = 117°. The Yamada-Winnewisser quasi-linearity parameter is found to be γ0 = 0.84, which is close to 1.0 as expected for a bent molecule. Since no experimental rovibrational spectrum has been reported thus far, this spectrum has been simulated from the ab initio potential energy and dipole moment surfaces. The amphoteric character of ZnOH is also discussed.

  18. A rigorous full-dimensional quantum dynamics study of tunneling splitting of rovibrational states of vinyl radical C 2 H 3

    DOE PAGES

    Yu, Hua-Gen; Song, Hongwei; Yang, Minghui

    2017-06-12

    Here, we report a rigorous quantum mechanical study of the rovibrational energy levels of vinyl radical C2H3. The calculations are carried out using a real two-component multi-layer Lanczos algorithm in a set of orthogonal polyspherical coordinates based on a recently developed accurate ab initio potential energy surface of C2H3. All well converged 158 vibrational bands up to 3200 cm-1 are determined, together with a comparison to previous calculations and experimental results. Our results show a remarkable multi-dimensional tunneling effect on the vibrational spectra of the radical. The vibrational tunneling splitting is substantially different from that of previous reduced dimensional calculations.more » The rotational constants of the fundamental vibrational bands of C2H3 are also given. It was found that the rovibrational states are strongly coupled, especially among those bending vibrational modes. Additionally, the perturbative iteration approach of Gruebele has been extended to assign the rovibrational energy levels of C2H3 without the requirement of explicit wavefunctions.« less

  19. Reduced dimension rovibrational variational calculations of the S{sub 1} state of C{sub 2}H{sub 2}. II. The S{sub 1} rovibrational manifold and the effects of isomerization

    SciTech Connect

    Changala, P. Bryan Baraban, Joshua H.; Field, Robert W.; Stanton, John F.; Merer, Anthony J.

    2014-01-14

    Reduced dimension variational calculations have been performed for the rovibrational level structure of the S{sub 1} state of acetylene. The state exhibits an unusually complicated level structure, for various reasons. First, the potential energy surface has two accessible conformers, trans and cis. The cis conformer lies about 2700 cm{sup −1} above the trans, and the barrier to cis-trans isomerization lies about 5000 cm{sup −1} above the trans minimum. The trans vibrations ν{sub 4} (torsion) and ν{sub 6} (asym. bend) interact very strongly by Darling-Dennison and Coriolis resonances, such that their combination levels and overtones form polyads with unexpected structures. Both conformers exhibit very large x{sub 36} cross-anharmonicity since the pathway to isomerization is a combination of ν{sub 6} and ν{sub 3} (sym. bend). Near the isomerization barrier, the vibrational levels show an even-odd K-staggering of their rotational levels as a result of quantum mechanical tunneling through the barrier. The present calculations address all of these complications, and reproduce the observed K-structures of the bending and C–C stretching levels with good qualitative accuracy. It is expected that they will assist with the assignment of the irregular patterns near the isomerization barrier.

  20. A model for the excitation of water in comets

    NASA Astrophysics Data System (ADS)

    Bockelee-Morvan, D.

    1987-07-01

    The vibrational and rotational excitation of the H2O molecule in cometary atmospheres is investigated using a model which includes infrared vibrational pumping by the solar radiation flux, thermal excitation by collisions, and radiation trapping in the rotational and rovibrational lines. The escape probability formalism is used for solving the radiative transfer problem. Steady state is not assumed in the rate equations, and the H2O rotational population distribution is computed as a function of distance to nucleus. The rotational line intensities are evaluated for an unresolved coma observed at a distance of 1 AU: several submillimeter lines should be easily detectable in moderately bright comets with cooled space telescopes such as ISO or FIRST. The model fails to explain the 6(16)-5(23)H2O radio line tentatively detected in two comets. Synthetic spectra and line intensities of the nu2 and nu3 bands are computed for typical observing conditions and instruments which are ground-based, in earth orbit, or aboard space probes.

  1. RESONANT CAVITY EXCITATION SYSTEM

    DOEpatents

    Baker, W.R.; Kerns, Q.A.; Riedel, J.

    1959-01-13

    An apparatus is presented for exciting a cavity resonator with a minimum of difficulty and, more specifically describes a sub-exciter and an amplifier type pre-exciter for the high-frequency cxcitation of large cavities. Instead of applying full voltage to the main oscillator, a sub-excitation voltage is initially used to establish a base level of oscillation in the cavity. A portion of the cavity encrgy is coupled to the input of the pre-exciter where it is amplified and fed back into the cavity when the pre-exciter is energized. After the voltage in the cavity resonator has reached maximum value under excitation by the pre-exciter, full voltage is applied to the oscillator and the pre-exciter is tunned off. The cavity is then excited to the maximum high voltage value of radio frequency by the oscillator.

  2. A new ab initio potential energy surface for the collisional excitation of HCN by para- and ortho-H2.

    PubMed

    Denis-Alpizar, Otoniel; Kalugina, Yulia; Stoecklin, Thierry; Vera, Mario Hernández; Lique, François

    2013-12-14

    We present a new four-dimensional potential energy surface for the collisional excitation of HCN by H2. Ab initio calculations of the HCN-H2 van der Waals complex, considering both molecules as rigid rotors, were carried out at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12a] level of theory using an augmented correlation-consistent triple zeta (aVTZ) basis set. The equilibrium structure is linear HCN-H2 with the nitrogen pointing towards H2 at an intermolecular separation of 7.20 a0. The corresponding well depth is -195.20 cm(-1). A secondary minimum of -183.59 cm(-1) was found for a T-shape configuration with the H of HCN pointing to the center of mass of H2. We also determine the rovibrational energy levels of the HCN-para-H2 and HCN-ortho-H2 complexes. The calculated dissociation energies for the para and ortho complexes are 37.79 cm(-1) and 60.26 cm(-1), respectively. The calculated ro-vibrational transitions in the HCN-H2 complex are found to agree by more than 0.5% with the available experimental data, confirming the accuracy of the potential energy surface.

  3. Inelastic collisions of ultracold triplet Rb2 molecules in the rovibrational ground state

    NASA Astrophysics Data System (ADS)

    Drews, Björn; Deiß, Markus; Jachymski, Krzysztof; Idziaszek, Zbigniew; Hecker Denschlag, Johannes

    2017-03-01

    Exploring and controlling inelastic and reactive collisions on the quantum level is a main goal of the developing field of ultracold chemistry. For this, the preparation of precisely defined initial atomic and molecular states in tailored environments is necessary. Here we present experimental studies of inelastic collisions of metastable ultracold Rb2 molecules in an array of quasi-1D potential tubes. In particular, we investigate collisions of molecules in the absolute lowest triplet energy level where any inelastic process requires a change of the electronic state. Remarkably, we find similar decay rates as for collisions between rotationally or vibrationally excited triplet molecules where other decay paths are also available. The decay rates are close to the ones for universal reactions but vary considerably when confinement and collision energy are changed. This might be exploited to control the collisional properties of molecules.

  4. Electronic structure, rovibrational, and dipole moment calculations for the AsCl molecule.

    PubMed

    Mourad, Khaled A; Abdulal, Saleh N; Korek, Mahmoud

    2016-02-01

    The potential energy curves of the 19 lowest-lying singlet and triplet electronic states in the (2S+1)Λ((+/-)) representation of the AsCl molecule have been investigated using the complete active space self-consistent field (CASSCF) with multireference configuration interaction (MRCI+Q) method including single and double excitations and with the Davidson correction. The harmonic frequency ω e, the internuclear distance R e, the dipole moment, and the electronic energy with respect to the ground state T e were calculated for the electronic states considered. By using the canonical functions approach, the eigenvalue E v, the rotational constant B v, and the abscissae of the turning points R min and R max were calculated for the electronic states up to the vibrational level v = 60. The values obtained in the present work agree well with corresponding values available in the literature for several electronic states. Fifteen new electronic states were investigated here for the first time.

  5. Inelastic collisions of ultracold triplet Rb2 molecules in the rovibrational ground state

    PubMed Central

    Drews, Björn; Deiß, Markus; Jachymski, Krzysztof; Idziaszek, Zbigniew; Hecker Denschlag, Johannes

    2017-01-01

    Exploring and controlling inelastic and reactive collisions on the quantum level is a main goal of the developing field of ultracold chemistry. For this, the preparation of precisely defined initial atomic and molecular states in tailored environments is necessary. Here we present experimental studies of inelastic collisions of metastable ultracold Rb2 molecules in an array of quasi-1D potential tubes. In particular, we investigate collisions of molecules in the absolute lowest triplet energy level where any inelastic process requires a change of the electronic state. Remarkably, we find similar decay rates as for collisions between rotationally or vibrationally excited triplet molecules where other decay paths are also available. The decay rates are close to the ones for universal reactions but vary considerably when confinement and collision energy are changed. This might be exploited to control the collisional properties of molecules. PMID:28332492

  6. The role of rotational excitation in the activated dissociative chemisorption of vibrationally excited methane on Ni(100).

    PubMed

    Juurlink, L B; Smith, R R; Utz, A L

    2000-01-01

    We have measured the sticking probability of methane excited to v = 1 of the v3 antisymmetric C-H stretching vibration on a clean Ni(100) surface as a function of rotational state (J = 0, 1, 2 and 3) and have investigated the effect of Coriolis-mixing on reactivity. The data span a wide range of kinetic energies (9-49 kJ mol-1) and indicate that rotational excitation does not alter reactivity by more than a factor of two, even at low molecular speeds that allow for considerable rotation of the molecule during the interaction with the surface. In addition, rotation-induced Coriolis-splitting of the v3 mode into F+, F0 and F- states does not significantly affect the reactivity for J = 1 at 49 kJ mol-1 translational energy, even though the nuclear motions of these states differ. The lack of a pronounced rotational energy effect in methane dissociation on Ni(100) suggests that our previous results for (v = 1, v3, J = 2) are representative of all rovibrational sublevels of this vibrational mode. These experiments shed light on the relative importance of rotational hindering and dynamical steering mechanisms in the dissociative chemisorption on Ni(100) and guide future attempts to accurately model methane dissociation on nickel surfaces.

  7. Rovibrational spectroscopic constants and fundamental vibrational frequencies for isotopologues of cyclic and bent singlet HC{sub 2}N isomers

    SciTech Connect

    Inostroza, Natalia; Fortenberry, Ryan C.; Lee, Timothy J.; Huang, Xinchuan

    2013-12-01

    Through established, highly accurate ab initio quartic force fields, a complete set of fundamental vibrational frequencies, rotational constants, and rovibrational coupling and centrifugal distortion constants have been determined for both the cyclic 1 {sup 1} A' and bent 2 {sup 1} A' DCCN, H{sup 13}CCN, HC{sup 13}CN, and HCC{sup 15}N isotopologues of HCCN. Spectroscopic constants are computed for all isotopologues using second-order vibrational perturbation theory (VPT2), and the fundamental vibrational frequencies are computed with VPT2 and vibrational configuration interaction (VCI) theory. Agreement between VPT2 and VCI results is quite good, with the fundamental vibrational frequencies of the bent isomer isotopologues in accord to within a 0.1-3.2 cm{sup –1} range. Similar accuracies are present for the cyclic isomer isotopologues. The data generated here serve as a reference for astronomical observations of these closed-shell, highly dipolar molecules using new, high-resolution telescopes and as reference for laboratory studies where isotopic labeling may lead to elucidation of the formation mechanism for the known interstellar molecule: X {sup 3} A' HCCN.

  8. Gas Phase Rovibrational Spectroscopy of Dmso, PART.I: when a Synchrotron Source Reveals AN Unusual Rotational Behaviour

    NASA Astrophysics Data System (ADS)

    Cuisset, Arnaud; Sadovskii, Dmitrii A.; Pirali, Olivier

    2013-06-01

    Many of us have enjoyed the spectacle of a spinning top influenced by friction: rotating rapidly about a stable stationary axis, the top loses slowly its angular momentum j (and energy), slows down gradually, and then, suddenly, its axis becomes unstable, the top wobbles, and an abrupt change of the top's position follows. In other words, the system undergoes a bifurcation. In the case of the tippe top, rotation about its lower point is stable at low values of angular momentum J and becomes unstable at large J. Something quite similar occurs in a freely rotating dimethylsulfoxyde (DMSO, (CH_3)_2SO) molecule. For the first time in such large polyatomic molecule a quantum bifurcation induced by a gyroscopic destabilization was observed. This unusual phenomenon in rotational dynamics was discovered in the rovibrational states of the bending fundamental ν_{23} band of DMSO whose high-resolution gas phase absorption spectrum was observed along with that of ν_{11} by Cuisset et al. using the exceptional properties of the AILES beamline in the Far-Infrared domain. A. Cuisset, O. Pirali, D. Sadovskii,Phys. Rev. Lett., 109,(094101), 2012. A. Cuisset, L. Nanobashvili, I. Smirnova, R. Bocquet, F. Hindle, G. Mouret, O. Pirali, P. Roy, D. Sadovskii,Chem. Phys. Lett., 492,(30),2010 J. B. Brubach et al., AIP Conf. Proc., 1214, (81), 2010.

  9. Rovibrational Spectroscopic Constants and Fundamental Vibrational Frequencies for Isotopologues of Cyclic and Bent Singlet HC2N isomers

    NASA Technical Reports Server (NTRS)

    Inostroza, Natalia; Fortenberry, Ryan C.; Huang, Xinchuan; Lee, Timothy J.

    2013-01-01

    Through established, highly-accurate ab initio quartic force fields (QFFs), a complete set of fundamental vibrational frequencies, rotational constants, and rovibrational coupling and centrifugal distortion constants have been determined for both the cyclic 1(sup 1) 1A' and bent 2(sup 1)A' DCCN, H(C13)CCN, HC(C-13)N, and HCC(N-15) isotopologues of HCCN. Spectroscopic constants are computed for all isotopologues using second-order vibrational perturbation theory (VPT2), and the fundamental vibrational frequencies are computed with VPT2 and vibrational configuration interaction (VCI) theory. Agreement between VPT2 and VCI results is quite good with the fundamental vibrational frequencies of the bent isomer isotopologues in accord to within a 0.1 to 3.2 / cm range. Similar accuracies are present for the cyclic isomer isotopologues. The data generated here serve as a reference for astronomical observations of these closed-shell, highly-dipolar molecules using new, high-resolution telescopes and as reference for laboratory studies where isotopic labeling may lead to elucidation of the formation mechanism for the known interstellar molecule: X 3A0 HCCN.

  10. Anharmonic Rovibrational Calculations of Singlet Cyclic C4 Using a New Ab Initio Potential and a Quartic Force

    NASA Technical Reports Server (NTRS)

    Wang, Xiaohong; Huang, Xinchuan; Bowman, Joel M.; Lee, Timothy J.

    2013-01-01

    We report a CCSD(T)/cc-pCV5Z quartic force field (QFF) and a semi-global CCSD(T)-F12b/aug-cc-pVTZ potential energy surface (PES) for singlet, cyclic C4. Vibrational fundamentals, combinations and overtones are obtained using vibrational second-order perturbation theory (VPT2) and the vibrational configurationinteraction (VCI) approach. Agreement is within 10 cm(exp -1) between the VCI calculated fundamentals on the QFF and PES using the MULTIMODE (MM) program, and VPT2 and VCI results agree for the fundamentals. The agreement between VPT2- QFF and MM-QFF results is also good for the C4 combinations and overtones. The J = 1 and J = 2 rovibrational energies are reported from both VCI (MM) on the PES and VPT2 on the QFF calculations. The spectroscopic constants of (12)C4 and two C(sub 2v)-symmetry, single (13)C-substituted isotopologues are presented, which may help identification of cyclic C4 in future experimental analyses or astronomical observations.

  11. Molecular plasmonics: The role of rovibrational molecular states in exciton-plasmon materials under strong-coupling conditions

    NASA Astrophysics Data System (ADS)

    Sukharev, Maxim; Charron, Eric

    2017-03-01

    We extend the model of exciton-plasmon materials to include a rovibrational structure of molecules using wave-packet propagations on electronic potential energy surfaces. Our model replaces conventional two-level emitters with more complex molecules, allowing us to examine the influence of alignment and vibrational dynamics on strong coupling with surface plasmon-polaritons. We apply the model to a hybrid system comprising a thin layer of molecules placed on top of a periodic array of slits. Rigorous simulations are performed for two types of molecular systems described by vibrational bound-bound and bound-continuum electronic transitions. Calculations reveal new features in transmission, reflection, and absorption spectra, including the observation of significantly higher values of the Rabi splitting and vibrational patterns clearly seen in the corresponding spectra. We also examine the influence of anisotropic initial conditions on optical properties of hybrid materials, demonstrating that the optical response of the system is significantly affected by an initial prealignment of the molecules. Our work demonstrates that prealigned molecules could serve as an efficient probe for the subdiffraction characterization of the near-field near metal interfaces.

  12. Energetics, structure, and rovibrational spectroscopic properties of the sulfurous anions SNO{sup −} and OSN{sup −}

    SciTech Connect

    Fortenberry, Ryan C.; Francisco, Joseph S.

    2015-11-14

    The SNO{sup −} and OSN{sup −} anions are shown in this work to be very stable negatively charged species in line with other recent work [T. Trabelsi et al., J. Chem. Phys. 143, 164301 (2015)]. Utilizing established quartic force field techniques, the structural and rovibrational data for these anions are produced. The SNO{sup −} anion is less linear and has weaker bonds than the corresponding neutral radical giving much smaller rotational constants. OSN{sup −} is largely unchanged in these regards with inclusion of the additional electron. The S–N bond is actually stronger, and the rotational constants of OSN{sup −} versus OSN are similar. The vibrational frequencies of SNO{sup −} are red-shifted from the radical while those in OSN{sup −} are mixed. OSN{sup −} has mixing of the stretching modes while the S–N and N–S stretches of SNO{sup −} are largely independent of one another. The ω{sub 3} stretches are much brighter in these anions than they are in the radicals, but the ω{sub 1} stretches are still the brightest.

  13. Potential interstellar noble gas molecules: ArOH+ and NeOH+ rovibrational analysis from quantum chemical quartic force fields

    NASA Astrophysics Data System (ADS)

    Theis, Riley A.; Fortenberry, Ryan C.

    2016-03-01

    The discovery of ArH+ in the interstellar medium has shown that noble gas chemistry may be of more chemical significance than previously believed. The present work extends the known chemistry of small noble gas molecules to NeOH+ and ArOH+. Besides their respective neonium and argonium diatomic cation cousins, these hydroxyl cation molecules are the most stable small noble gas molecules analyzed of late. ArOH+ is once again more stable than the neon cation, but both are well-behaved enough for a complete quartic force field analysis of their rovibrational properties. The Ar-O bond in ArOH+ , for instance, is roughly three-quarters of the strength of the Ar-H bond in ArH+ highlighting the rigidity of this system. The rotational constants, geometries, and vibrational frequencies for both molecules and their various isotopologues are computed from ab initio quantum chemical theory at high-level, and it is shown that these cations may form in regions where peroxy or weakly-bound alcohols may be present. The resulting data should be of significant assistance for the laboratory or observational analysis of these potential interstellar molecules.

  14. [Rovibrational state distributions of H2 in collisional energy transfer between NaK (6(1)sigma(+)) and H2].

    PubMed

    Wang, Shu-Ying; Dai, Kang; Liu, Jing; Shen, Yi-Fan

    2012-12-01

    The electronic to rovibrational energy transfer between the high-lying 6(1)sigma(+) state of NaK and H2 was investigated. The 6(1)sigma(+) state was excited using the optical-optical double resonance technique. Radiative processes were monitored by fluorescence from the 6(1)sigma(+) state to the ground 1(1)sigma(+) state. The CARS (coherent anti-Stokes Raman scattering) spectral technique was used to probe the internal state distribution of collisionally-populated H2 molecules. The scanned CARS spectra reveal that during E-V, R energy transfer processes H2 molecules are produced at v = 1, 2 and 3 levels. The semilog plot of the time-resolved H2 (3, 1) CARS intensity was obtained at a pressure of 4 x 10(4) Pa of H2. The slop yields an effective quenching rate of 8.09 x 10(5) s(-1). Analogically, for (3, 2), (3, 3) and (3, 5) levels, the quenching rates are 6.11 x 10(5), 4.32 x 10(5) and 2.45 x 10(5) s(-1), respectively. For (3, 1), (3, 2), (3, 3) and (3, 5) levels, the population ratios were obtained from scanned CARS spectral peaks. For (1, 1), (2, 1), (2, 2) and (2,3) levels, from scanned CARS spectral peaks two possible population ratios were yielded. Through shape simulations of time resolved CARS profiles under a kinetic model the actual population ratios were determined. The n2/n1, n3/n1, n4/n1, n5/n1, n6/n1, n7/n1 and n8/n1 are 0.51, 0.97, 0.45, 0.18, 0.10, 0.26 and 0.31, where n1, n2, n3, n4, n5, n6, n7 and n8 represent the number densities of H2 at (3, 1), (2, 1), (1, 1), (3, 3), (2, 3), (2, 2), (3, 2) and (3, 5) levels, respectively. The H2 molecules produced by energy transfer process were populated by 26% at the v = 1 level, 21% at v = 2 and 53% at v = 3. The major vibrational energy [(9.0 +/- 2.7) x 10(3) cm(-1)] release and the minor rotational energy [(3.9 +/- 1.1) x 10(2) cm(-1)] release are shown. Based on the Stern-Volmer equation, the radiative lifetime is (5.0 +/- 1.3) ns for the 6(1)sigma(+) state, the total rate coefficient for deactivation of

  15. Electronic Raman scattering with excitation between localized states observed in the zinc M{sub 2,3} soft x-ray spectra of ZnS

    SciTech Connect

    Zhou, L.; Callcott, T.A.; Jia, J.J.

    1997-04-01

    Zn M{sub 2,3} soft x-ray fluorescence (SXF) spectra of ZnS and ZnS{sub .5}Se{sub .5} excited near threshold show strong inelastic scattering effects that can be explained using a simple model and an inelastic scattering theory based on second order perturbation theory. This scattering is often called electronic resonance Raman scattering. Tulkki and Aberg have developed this theory in detail for atomic systems, but their treatment can be applied to solid systems by utilizing electronic states characteristic of solids rather than of atomic systems.

  16. Towards completing the cyclopropenylidene cycle: rovibrational analysis of cyclic N3(+), CNN, HCNN(+), and CNC().

    PubMed

    Fortenberry, Ryan C; Lee, Timothy J; Huang, Xinchuan

    2017-08-30

    The simple aromatic hydrocarbon, cyclopropenylidene (c-C3H2), is a known, naturally-occurring molecule. The question remains as to whether its isoelectronic, cyclic, fellow aromatics of c-N3(+), c-CNN, HCNN(+), and c-CNC(-) are as well. Each of these are exciting objects for observation of Titan, and the rotational constants and vibrational frequencies produced here will allow for remote sensing of Titan's atmosphere or other astrophysical or terrestrial sources. None of these four aromatic species are vibrationally strong absorbers/emitters, but the two ions, HCNN(+) and c-CNC(-), have dipole moments of greater than 3 D and 1 D, respectively, making them good targets for rotational spectroscopic observation. Each of these molecules is shown here to exhibit its own, unique vibrational properties, but the general trends put the vibrational behavior for corresponding fundamental modes within close ranges of one another, even producing nearly the same heavy atom, symmetric stretching frequencies for HCNN(+) and c-C3H2 at 1600 cm(-1). The c-N3(+) cation is confirmed to be fairly unstable and has almost no intensity in its ν2 fundamental. Hence, it will likely remain difficult to characterize experimentally.

  17. Computational Investigations of Rovibrational Quenching of HD due to Collisions in the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Goodman Veazey, Clark; Wan, Yier; Yang, Benhui H.; Stancil, P.

    2017-06-01

    When conducting an examination of distant astronomical objects, scientists rely on measurements derived from astronomical observations of these objects, which are primarily collected using spectroscopy. In order to interpret spectroscopic data collected on astronomical objects, it is necessary to have a background of accurate dynamical information on interstellar molecules at one’s disposal. Seeing as most of the observable infrared radiation in the universe is emitted by molecules excited by collisional processes in the interstellar gas, generating accurate data on the rate of molecular collisions is of salient interest to astronomical endeavors.The collisional system we will be focusing on here is He-HD, an atom-diatom system in which He collides with HD. We are primarily interested in the cooling capabilities of this system, as these species are predicted to have played an important role in the formation of primordial stars, which emerged from a background composed solely of Hydrogen, Helium, and their compounds. HD is being investigated because it has a finite dipole moment and is hence a powerful radiator, and He due to its relative abundance in the early universe. Using a hybrid OpenMP/MPI adaption (vrrm) of a public-domain scattering package, cross sections for He-HD collisions are computed for a swathe of both rotational and vibrational states across a range of relevant kinetic energies, then integrated to produce rate coefficients. Due to the vast computational requirements for performing these operations, the use of high-powered computational resources is necessary.The work of CV was funded by a UGA Center for Undergraduate Research Opportunities award. We thank the University of Georgia GACRC and NERSC at Lawrence-Berkeley for computational resources and Brendan McLaughlin for assistance.

  18. Ab initio dipole moment and theoretical rovibrational intensities in the electronic ground state of PH 3

    NASA Astrophysics Data System (ADS)

    Yurchenko, Sergei N.; Carvajal, Miguel; Thiel, Walter; Jensen, Per

    2006-09-01

    We report a six-dimensional CCSD(T)/aug-cc-pVTZ dipole moment surface for the electronic ground state of PH 3 computed ab initio on a large grid of 10 080 molecular geometries. Parameterized, analytical functions are fitted through the ab initio data, and the resulting dipole moment functions are used, together with a potential energy function determined by refining an existing ab initio surface in fittings to experimental wavenumber data, for simulating absorption spectra of the first three polyads of PH 3, i.e., ( ν2, ν4), ( ν1, ν3, 2 ν2, 2 ν4, ν2 + ν4), and ( ν1 + ν2, ν3 + ν2, ν1 + ν4, ν3 + ν4, 2 ν2 + ν4, ν2 + 2 ν4, 3 ν2, 3 ν4). The resulting theoretical transition moments show excellent agreement with experiment. A line-by-line comparison of the simulated intensities of the ν2/ ν4 band system with 955 experimental intensity values reported by Brown et al. [L.R. Brown, R.L. Sams, I. Kleiner, C. Cottaz, L. Sagui, J. Mol. Spectrosc. 215 (2002) 178-203] gives an average absolute percentage deviation of 8.7% (and a root-mean-square deviation of 0.94 cm -1 for the transition wavenumbers). This is very remarkable since the calculations rely entirely on ab initio dipole moment surfaces and do not involve any adjustment of these surfaces to reproduce the experimental intensities. Finally, we predict the line strengths for transitions between so-called cluster levels (near-degenerate levels formed at high rotational excitation) for J up to 60.

  19. Portable vibration exciter

    NASA Technical Reports Server (NTRS)

    Beecher, L. C.; Williams, F. T.

    1970-01-01

    Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.

  20. Excited charmed mesons

    SciTech Connect

    Butler, J.N.; Shukla, S.

    1995-05-01

    The experimental status of excited charmed mesons is reviewed and is compared to theoretical expectations. Six states have been observed and their properties are consistent with those predicted for excited charmed states with orbital angular momentum equal to one.

  1. Rovibrational states of N3- and CO2 up to high J: a theoretical study beyond fc-CCSD(T).

    PubMed

    Sebald, Peter; Stein, Christopher; Oswald, Rainer; Botschwina, Peter

    2013-12-19

    An accurate near-equilibrium potential energy surface (PES) has been constructed for the azide ion (N(3)(-)) on the basis of coupled cluster calculations up to CCSDTQ (Kállay, M.; Surján, P. R. J. Chem. Phys. 2001, 115, 2945.), with contributions from inner-shell correlation and special relativity being taken into account as well. A larger number of rovibrational states has been investigated by variational calculations with Watson's isomorphic Hamiltonian for linear molecules. Analogous calculations for CO2 demonstrate the high quality of this type of calculations. The G(v) values of the symmetric stretching and bending vibration of 14N(3)(-) are predicted to be ν1 = 1307.9 cm(-1) and ν2 = 629.3 cm(-1), with an uncertainty of ca. 1 cm(-1). Fermi resonance is less pronounced for the lower polyads of 14N(3)(-) compared with 12C16O2 but is as strong as in CO2 for the lowest diad of isotopologue 15-14-15. The band origin of the antisymmetric stretching vibration of 14N(3)(-) is calculated to be ν3 = 1986.4 cm(-1), only 0.1 cm(-1) lower than the experimental value. The corresponding vibrational transition dipole moment is predicted to be as large as μ = 0.476 D, 46% higher than calculated for CO2. The perturbed combination tone (01(1)1), which was accessible through diode laser IR spectroscopy, undergoes anharmonic interaction with at least two other vibrational states.

  2. Near-infrared spectra and rovibrational dynamics on a four-dimensional ab initio potential energy surface of (HBr)2.

    PubMed

    Castillo-Chará, J; McIntosh, A L; Wang, Z; Lucchese, R R; Bevan, J W

    2004-06-08

    Supersonic jet investigations of the (HBr)(2) dimer have been carried out using a tunable diode laser spectrometer to provide accurate data for comparison with results from a four-dimensional (4-D) ab initio potential energy surface (PES). The near-infrared nu(1) (+/-), nu(2) (+/-), and (nu(1)+nu(4))(-) bands of (H (79)Br)(2), (H (79)Br-H (81)Br), and (H (81)Br)(2) isotopomers have been recorded in the range 2500-2600 cm(-1) using a CW slit jet expansion with an upgraded near-infrared diode laser spectrometer. The 4-D PES has been calculated for (HBr)(2) using second-order Møller-Plesset perturbation theory with an augmented and polarized 6-311G basis set. The potential is characterized by a global minimum occurring at the H bond structure with the distance between the center of masses (CM) of the monomer being R(CM)=4.10 A with angles theta(A)=10 degrees, theta(B)=100 degrees and a well depth of 692.2 cm(-1), theta(A) is the angle the HBr bond of monomer A makes with the vector from the CM of A to the CM of B, and theta(B) is the corresponding angle monomer B makes with the same CM-CM vector. The barrier for the H interchange occurs at the closed C(2h) structure for which R(CM)=4.07 A, theta(A)=45 degrees, theta(B)=135 degrees, and the barrier height is 73.9 cm(-1). The PES was fitted using a linear-least squares method and the rovibrational energy levels of the complex were calculated by a split pseudospectral method. The spectroscopic data provide accurate molecular parameters for the dimer that are then compared with the results predicted on the basis of the 4-D ab initio PES.

  3. Isotope effects in the CO dimer: Millimeter wave spectrum and rovibrational calculations of (12C18O)2

    NASA Astrophysics Data System (ADS)

    Surin, L. A.; Fourzikov, D. N.; Giesen, T. F.; Schlemmer, S.; Winnewisser, G.; Panfilov, V. A.; Dumesh, B. S.; Vissers, G. W. M.; van der Avoird, A.

    2006-09-01

    The millimeter wave spectrum of the isotopically substituted CO dimer, (C12O18)2, was studied with the Orotron jet spectrometer, confirming and extending a previous infrared study [A. R. W. McKellar, J. Mol. Spectrosc. 226, 190 (2004)]. A very dilute gas mixture of CO in Ne was used, which resulted in small consumption of C12O18 sample gas and produced cold and simple spectra. Using the technique of combination differences together with the data from the infrared work, six transitions in the 84-127GHz region have been assigned. They belong to two branches, which connect four low levels of A+ symmetry to three previously unknown levels of A- symmetry. The discovery of the lowest state of A- symmetry, which corresponds to the projection K =0 of the total angular momentum J onto the intermolecular axis, identifies the geared bending mode of the C12O18 dimer at 3.607cm-1. Accompanying rovibrational calculations using a recently developed hybrid potential from ab initio coupled cluster [CCSD(T)] and symmetry-adapted perturbation theory calculations [G. W. M. Vissers et al., J. Chem. Phys. 122, 054306 (2005)] gave very good agreement with experiment. The isotopic dependence of the A+/A- energy splitting, the intermolecular separation R, and the energy difference of two ground state isomers, which change significantly when O18 or C13 are substituted into the normal (C12O16)2 isotopolog [L. A. Surin et al., J. Mol. Spectrosc. 223, 132 (2004)], was explained by these calculations. It turns out that the change in anisotropy of the intermolecular potential with respect to the shifted monomer centers of mass is particularly significant.

  4. Calculation of the polarization of light emitted during electron-impact excitation of Ba+

    NASA Astrophysics Data System (ADS)

    Bostock, Christopher J.; Fursa, Dmitry V.; Bray, Igor

    2014-06-01

    The measurements of Crandall et al. [Phys. Rev. A 10, 141 (1974), 10.1103/PhysRevA.10.141] for the polarization of light emitted during electron-impact excitation of Ba+ are in significant disagreement with relativistic distorted wave scattering theory calculations of Sharma et al. [Phys. Rev. A 83, 062701 (2011), 10.1103/PhysRevA.83.062701]. The relativistic convergent close-coupling (RCCC) method is applied to the problem and the discrepancy between theory and experiment is resolved across the full range of energies measured. Furthermore, the oscillations in the polarization fraction measurements at low energies near threshold are reproduced by the RCCC calculations and linked to the formation of autoionizing states of neutral Ba.

  5. Statistical and nonstatistical nonadiabatic photodissociation from the first excited state of the hydroxymethyl radical

    SciTech Connect

    Yarkony, David R.

    2005-02-22

    Photodissociation of hydroxymethyl (H{sub 2}COD) from the first excited state, a Rydberg 3s state, can produce either H+HCOD or H{sub 2}CO+D. These processes involve a seam of conical intersections. An analysis of the seam is reported based on a pointwise determination of the three gradient vectors that characterize a conical intersection: the energy difference gradient and the coupling gradient, which span the branching space, and the gradient of the average energy. These data are used to understand why H, but not D is produced at energies near threshold, the difference in the recoil anisotropy for H and D dissociation, and whether H or D will be produced impulsively or after formation of an intermediate complex.

  6. Towards pair production near threshold with unstable particle effective theory

    SciTech Connect

    Beneke, M.; Kauer, N.; Signer, A.; Zanderighi, G.; /Fermilab

    2004-10-01

    We illustrate the use of effective theory techniques to describe processes involving unstable particles close to resonance. First, we present the main ideas in the context of a scalar resonance in an Abelian gauge-Yukawa model. We then outline the necessary modifications to describe W-pair production close to threshold in electron-positron collisions.

  7. Proton radiography based on near-threshold Cerenkov radiation

    DOEpatents

    van Bibber, Karl A.; Dietrich, Frank S.

    2003-01-01

    A Cerenkov imaging system for charged particle radiography that determines the energy loss of the charged particle beam passing through an object. This energy loss information provides additional detail on target densities when used with traditional radiographic techniques like photon or x-ray radiography. In this invention a probe beam of 800 MeV to 50 GeV/c charged particles is passed through an object to be imaged, an imaging magnetic spectrometer, to a silicon aerogel Cerenkov radiator where the charged particles emitted Cerenkov light proportional to their velocity. At the same beam focal plane, a particle scintillator produces a light output proportional to the incident beam flux. Optical imaging systems relay the Cerenkov and scintillator information to CCD's or other measurement equipment. A ratio between the Cerenkov and scintillator is formed, which is directly proportional to the line density of the object for each pixel measured. By rotating the object, tomographic radiography may be performed. By applying pulses of beam, discrete time-step movies of dynamic objects may be made.

  8. Triple Photoionization of Neon and Argon Near Threshold

    NASA Astrophysics Data System (ADS)

    Bluett, Jaques B.; Lukić, Dragan; Sellin, Ivan A.; Whitfield, Scott B.; Wehlitz, Ralf

    2003-05-01

    The threshold behavior of the triple ionization cross-section of neon and argon was investigated using monochromatized synchrotron radiation and ion time-of-flight spectrometry. The Ne^3+ and Ar^3+ cross-sections are found to follow the Wannier power law(G.H. Wannier, Phys. Rev. 90), 817 (1953). consistent with a Wannier exponent of 2.162 predicted by theory. This is also consistent with the findings of Samson and Angel(J.A.R. Samson and G.C. Angel, Phys. Lett. 61), 1584 (1988). for the case of Ne. In the case of argon we find a much shorter range of validity than for neon.

  9. Near-Threshold Production of ϕ Mesons in pp Collisions

    NASA Astrophysics Data System (ADS)

    Hartmann, M.; Maeda, Y.; Keshelashvili, I.; Koch, H. R.; Mikirtytchiants, S.; Barsov, S.; Borgs, W.; Büscher, M.; Dimitrov, V. I.; Dymov, S.; Hejny, V.; Kleber, V.; Koptev, V.; Kulessa, P.; Mersmann, T.; Merzliakov, S.; Mussgiller, A.; Nekipelov, M.; Nioradze, M.; Ohm, H.; Pysz, K.; Schleichert, R.; Stein, H. J.; Ströher, H.; Watzlawik, K.-H.; Wüstner, P.

    2006-06-01

    The pp→ppϕ reaction has been studied at the Cooler Synchrotron COSY-Jülich, using the internal beam and ANKE facility. Total cross sections have been determined at three excess energies γ near the production threshold. The differential cross section closest to threshold at γ=18.5MeV exhibits a clear S wave dominance as well as a noticeable effect due to the proton-proton final-state interaction. Taken together with data for ppω production, a significant enhancement of the ϕ/ω ratio of a factor 8 is found compared to predictions based on the Okubo-Zweig-Iizuka rule.

  10. Associated strangeness production in pp collisions near threshold

    NASA Astrophysics Data System (ADS)

    Winter, P.

    2004-08-01

    Motivated by the ongoing discussion concerning the nature of the scalar resonances f0(980) and a0(980), the COSY-11 collaboration has taken exclusive data on the pp → ppK+K- reaction near the production threshold. A first total cross section σ = (1.80 ± 0.27-0.35+0.28) nb for the excess energy Q = 17 MeV has been determined. In contrary to the η, ω, and η' single meson production studies which clearly show the strong pp final state interaction (FSI), the cross section values obtained at COSY-11 and DISTO can be both described by a fit with a four-body phase space including the proton-proton final state interaction as well as with one-meson exchange calculations neglecting FSI effects. Therefore, one might think about a compensation of the strong pp interaction through a pK- FSI effect or an additional degree of freedom caused by the four-body final state. In the latter case, strong FSI effects can be expected at Q-values very close to the K+K- production threshold. Such a motivation triggered — in combination with the investigation of the KK¯ interaction being relevant to the structure of the f0 (980) — further measurements at the excess energies Q = 10 and Q = 28 MeV at COSY-11.

  11. Nonexponential decay laws in perturbation theory of near threshold eigenvalues

    NASA Astrophysics Data System (ADS)

    Dinu, Victor; Jensen, Arne; Nenciu, Gheorghe

    2009-01-01

    We consider a two channel model of the form Hε=[Hop0 0E0]+ε[0W12W210] on H =Hop⊕C. The operator Hop is assumed to have the properties of a Schrödinger operator in odd dimensions, with a threshold at zero. As the energy parameter E0 is tuned past the threshold, we consider the survival probability |⟨Ψ0,e-itHεΨ0⟩|2, where Ψ0 is the eigenfunction corresponding to eigenvalue E0 for ε =0. We find nonexponential decay laws for ε small and E0 close to zero provided that the resolvent of Hop is not at least Lipschitz continuous at the threshold zero.

  12. Near-threshold production of phi mesons in pp collisions.

    PubMed

    Hartmann, M; Maeda, Y; Keshelashvili, I; Koch, H R; Mikirtytchiants, S; Barsov, S; Borgs, W; Büscher, M; Dimitrov, V I; Dymov, S; Hejny, V; Kleber, V; Koptev, V; Kulessa, P; Mersmann, T; Merzliakov, S; Mussgiller, A; Nekipelov, M; Nioradze, M; Ohm, H; Pysz, K; Schleichert, R; Stein, H J; Ströher, H; Watzlawik, K-H; Wüstner, P

    2006-06-23

    The pp-->ppphi reaction has been studied at the Cooler Synchrotron COSY-Jülich, using the internal beam and ANKE facility. Total cross sections have been determined at three excess energies epsilon near the production threshold. The differential cross section closest to threshold at epsilon=18.5 MeV exhibits a clear S wave dominance as well as a noticeable effect due to the proton-proton final-state interaction. Taken together with data for ppomega production, a significant enhancement of the phi/omega ratio of a factor 8 is found compared to predictions based on the Okubo-Zweig-Iizuka rule.

  13. Sub-millimeter wave spectroscopy of the C 3H radical: Ro-vibrational transitions from ground to the lowest bending state

    NASA Astrophysics Data System (ADS)

    Caris, M.; Giesen, T. F.; Duan, C.; Müller, H. S. P.; Schlemmer, S.; Yamada, K. M. T.

    2009-02-01

    Linear C 3H in its (X 2Π) electronic ground state possesses strong Renner-Teller coupling in the two lowest bending modes, ν4 and ν5. The 2Σμ level of the v4 = 1 bending mode is shifted towards lower energies and is supposed to lie only 20.3 cm -1 above the ground state [S. Yamamoto, S. Saito, H. Suzuki, S. Deguchi, N. Kaifu, S. Ishikawa, M. Ohishi, Astrophys. J. 348 (1990) 363]. In the present study, first measurements of ro-vibrational transitions from the 2Π3/2 ground state to the 2Σμ lowest vibrational state were performed using a Terahertz spectrometer equipped with a supersonic jet nozzle. Rotational levels of the 2Π3/2 and v4 = 1( 2Σμ) state are close in energy and a crossing of the rotational energy ladders occurs between J = 24.5 and 25.5. A strong vibronic coupling leads to a significant intensity enhancement of 2Π3/2 - 2Σμ ro-vibrational transitions. The search for ro-vibrational transitions was facilitated by measurements on pure rotational transitions in the 2Π1/2, 2Π3/2 and v4 = 1( 2Σμ) states, substantially extending the former data set published by Yamamoto et al. Data analysis yields an accurate value for the v4 = 1( 2Σμ) energy level which has been found to lie 609.9771(42) GHz or 20.34664(14) cm -1 above the 2Π ground state. Furthermore, the value of the vibronic coupling constant β has been improved significantly and determined as 1231.77(51) MHz. The new set of spectroscopic parameters obtained in the present study permits very reliable frequency predictions into the Terahertz region.

  14. Extension of the MIRS computer package for the modeling of molecular spectra: From effective to full ab initio ro-vibrational Hamiltonians in irreducible tensor form

    NASA Astrophysics Data System (ADS)

    Nikitin, A. V.; Rey, M.; Champion, J. P.; Tyuterev, Vl. G.

    2012-07-01

    The MIRS software for the modeling of ro-vibrational spectra of polyatomic molecules was considerably extended and improved. The original version [Nikitin AV, Champion JP, Tyuterev VlG. The MIRS computer package for modeling the rovibrational spectra of polyatomic molecules. J Quant Spectrosc Radiat Transf 2003;82:239-49.] was especially designed for separate or simultaneous treatments of complex band systems of polyatomic molecules. It was set up in the frame of effective polyad models by using algorithms based on advanced group theory algebra to take full account of symmetry properties. It has been successfully used for predictions and data fitting (positions and intensities) of numerous spectra of symmetric and spherical top molecules within the vibration extrapolation scheme. The new version offers more advanced possibilities for spectra calculations and modeling by getting rid of several previous limitations particularly for the size of polyads and the number of tensors involved. It allows dealing with overlapping polyads and includes more efficient and faster algorithms for the calculation of coefficients related to molecular symmetry properties (6C, 9C and 12C symbols for C3v, Td, and Oh point groups) and for better convergence of least-square-fit iterations as well. The new version is not limited to polyad effective models. It also allows direct predictions using full ab initio ro-vibrational normal mode Hamiltonians converted into the irreducible tensor form. Illustrative examples on CH3D, CH4, CH3Cl, CH3F and PH3 are reported reflecting the present status of data available. It is written in C++ for standard PC computer operating under Windows. The full package including on-line documentation and recent data are freely available at http://www.iao.ru/mirs/mirs.htm or http://xeon.univ-reims.fr/Mirs/ or http://icb.u-bourgogne.fr/OMR/SMA/SHTDS/MIRS.html and as supplementary data from the online version of the article.

  15. Rovibrational internal energy transfer and dissociation of N2(1Σg+)-N(4S(u)) system in hypersonic flows.

    PubMed

    Panesi, Marco; Jaffe, Richard L; Schwenke, David W; Magin, Thierry E

    2013-01-28

    A rovibrational collisional model is developed to study energy transfer and dissociation of N(2)((1)Σ(g)(+)) molecules interacting with N((4)S(u)) atoms in an ideal isochoric and isothermal chemical reactor. The system examined is a mixture of molecular nitrogen and a small amount of atomic nitrogen. This mixture, initially at room temperature, is heated by several thousands of degrees Kelvin, driving the system toward a strong non-equilibrium condition. The evolution of the population densities of each individual rovibrational level is explicitly determined via the numerical solution of the master equation for temperatures ranging from 5000 to 50,000 K. The reaction rate coefficients are taken from an ab initio database developed at NASA Ames Research Center. The macroscopic relaxation times, energy transfer rates, and dissociation rate coefficients are extracted from the solution of the master equation. The computed rotational-translational (RT) and vibrational-translational (VT) relaxation times are different at low heat bath temperatures (e.g., RT is about two orders of magnitude faster than VT at T = 5000 K), but they converge to a common limiting value at high temperature. This is contrary to the conventional interpretation of thermal relaxation in which translational and rotational relaxation timescales are assumed comparable with vibrational relaxation being considerable slower. Thus, this assumption is questionable under high temperature non-equilibrium conditions. The exchange reaction plays a very significant role in determining the dynamics of the population densities. The macroscopic energy transfer and dissociation rates are found to be slower when exchange processes are neglected. A macroscopic dissociation rate coefficient based on the quasi-stationary distribution, exhibits excellent agreement with experimental data of Appleton et al. [J. Chem. Phys. 48, 599-608 (1968)]. However, at higher temperatures, only about 50% of dissociation is found to

  16. Rovibrational constants of the ground and ν12 = 1 states of C2D4 by high-resolution synchrotron FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Tan, T. L.; Gabona, M. G.; Appadoo, Dominique R. T.; Godfrey, Peter D.; McNaughton, Don

    2014-09-01

    The Fourier transform infrared (FTIR) absorption spectrum of the ν12 fundamental band of ethylene-d4 (C2D4) was recorded in the 1000-1150 cm-1 region with a resolution of 0.00096 cm-1 using the THz/far-infrared beamline of the Australian Synchrotron. Upper state (ν12 = 1) rovibrational constants consisting of three rotational constants and up to five quartic constants were improved by assigning and fitting 3950 rovibrational transitions using Watson’s A-reduced and S-reduced Hamiltonians in the Ir representation. The band centres of the unperturbed A-type ν12 band are found to be 1076.984958(14) cm-1 and 1076.984813(14) cm-1 for A-reduced and S-reduced Hamiltonians respectively. The present analysis, covering a wider wavenumber range and higher J and Kc values (up to 58) than previous studies, yielded upper state constants including the band centre which are more accurate than previously reported. The rms deviation of the upper state (ν12 = 1) fit is 0.00040 cm-1 in the A-reduction and 0.00041 cm-1 in the S-reduction. Improved ground state rovibrational constants were also determined from the fit of 3151 ground state combination differences (GSCD) from the presently-assigned transitions of the ν12 band of C2D4 using Watson’s A-reduced and S-reduced Hamiltonians in the Ir representation. The rms deviation of the GSCD fit is 0.00036 cm-1 in the A-reduction and 0.00035 cm-1 in the S-reduction. The ground state constants of C2D4 derived from the experimental GSCD fit are in good agreement with those from theoretical calculations using the B3LYP/cc-pVTZ, MP2/cc-pVTZ, and CSSD/cc-pVTZ levels, up to five quartic constants.

  17. Acoustically excited heated jets. 1: Internal excitation

    NASA Technical Reports Server (NTRS)

    Lepicovsky, J.; Ahuja, K. K.; Brown, W. H.; Salikuddin, M.; Morris, P. J.

    1988-01-01

    The effects of relatively strong upstream acoustic excitation on the mixing of heated jets with the surrounding air are investigated. To determine the extent of the available information on experiments and theories dealing with acoustically excited heated jets, an extensive literature survey was carried out. The experimental program consisted of flow visualization and flowfield velocity and temperature measurements for a broad range of jet operating and flow excitation conditions. A 50.8-mm-diam nozzle was used for this purpose. Parallel to the experimental study, an existing theoretical model of excited jets was refined to include the region downstream of the jet potential core. Excellent agreement was found between theory and experiment in moderately heated jets. However, the theory has not yet been confirmed for highly heated jets. It was found that the sensitivity of heated jets to upstream acoustic excitation varies strongly with the jet operating conditions and that the threshold excitation level increases with increasing jet temperature. Furthermore, the preferential Strouhal number is found not to change significantly with a change of the jet operating conditions. Finally, the effects of the nozzle exit boundary layer thickness appear to be similar for both heated and unheated jets at low Mach numbers.

  18. Study of the rovibrational intensities of tetrahedral molecules and prediction of the pentad poliade of {sup 12}CD{sub 4}

    SciTech Connect

    Kaarour, A. Ouardi, O. Meskine, M.

    2015-03-30

    The use of tensor models adapted to tetrahedral molecules such CH{sub 4}, SiH{sub 4}, G{sub e}H{sub 4}... that use mathematical tools (group theory, irreducible tensor operators) and the characteristics of symmetrical molecules, gives good results. Starting from an experimental spectrum, we can calculate some parameters of the Hamiltonian and consequently the energy levels. Once the line positions are determined, we calculate the parameters of the dipole moment of these molecules and consequently the rovibrational intensities. Both software STDS and SPVIEW, we determined the parameters of the Hamiltonian and those of the dipole moment.

  19. Multimode calculations of rovibrational energies and dipole transition intensities for polyatomic molecules with torsional motion: application to H{sub 2}O{sub 2}.

    SciTech Connect

    Carter, S.; Sharma, A. R.; Bowman, J. M.

    2011-01-01

    We report rigorous calculations of rovibrational energies and dipole transition intensities for hydrogen peroxide using a new version of MULTIMODE as applied to molecules with torsional (reaction path) motion. The key features which permit such calculations for moderately sized polyatomic molecules of this general type are briefly described. A previous, accurate potential energy surface and a new high-level ab initio dipole moment surface are employed in these calculations. Detailed comparisons are made with high-resolution experimental spectral intensities from the HITRAN database.

  20. Effects of new rate constants of transitions from vibrational levels on non-LTE radiation in ro-vibrational bands used for H2O retrieval in the middle atmosphere

    NASA Astrophysics Data System (ADS)

    Manuilova, Rada; Kutepov, Alexander; Feofilov, Artem; Yankovsky, Valentine A.

    In this work, we investigate the sensitivity of the H _{2}O vibrational level populations and ro-vibrational spectra in the mesosphere and lower thermosphere (MLT) to new values of rate constants for the collision-induced transitions from the upper vibrational levels of H _{2}O molecule. This study contributes to the development of the H _{2}O non-equilibrium radiation model used for water vapor altitude distribution retrieval from the MLT radiation measurements. Our model accounts for 13 excited vibrational states up to energies 7445 cm-1 (the upper levels are 002, 101, 200) [Feofilov et al., 2009]. The model takes into account 54 vibrational-translational (V-T) and vibrational-vibrational (V-V) energy exchange processes at collisions of H _{2}O with N _{2}, O _{2} and O. The 32 ro-vibrational transitions forming 1.4, 1.9, 2.7, 3.2, 4.7 and 6.3 mum water vapor radiation bands are considered. Currently, the rate constants of intermolecular transitions between vibrational levels at collisions with N _{2} and O _{2} are known only for the transitions (010-000) and (001,100-020). In our model of H _{2}O vibrational level kinetics [Feofilov et al., 2009], we assumed that for all collisional transitions, at which the bending mode quantum number, v _{2}, increases by 2: H _{2}O(v _{1},v _{2},v _{3}) + M = H _{2}O(v _{1}-1,v _{2}+2,v _{3}) + M H _{2}O(v _{1},v _{2},v _{3}) + M = H _{2}O(v _{1},v _{2}+2,v _{3}-1) + M (1) the rate constants are equal to that of the process H _{2}O(001, 100) + M = H _{2}O(020) + M. Based on the analysis of currently available experimental and theoretical data, we have updated k, the rate constant of transitions (002, 101) -> 021 and (101, 200) -> 120, and estimated the effect of a new rate on the H _{2}O vibrational levels populations and limb radiation spectra. The “upper limit” of the effect was estimated using the same rate constant k for all processes of type (1), excluding process (001, 100) -> 020. The H _{2}O vibrational levels

  1. Relaxation of vibrational levels H2O (002, 101, 200): effect of new rate constants on the H2O vibrational level populations and ro-vibrational spectra in the mesosphere and lower thermosphere

    NASA Astrophysics Data System (ADS)

    Manuilova, Rada; Feofilov, Artem; Kutepov, Alexander; Yankovsky, Valentine

    2014-05-01

    In this work, we investigate the sensitivity of the H2O vibrational level populations and ro-vibrational spectra in the mesosphere and lower thermosphere (MLT) to new values of rate constants for the collision-induced transitions from the upper vibrational levels of H2O molecule. This study contributes to the development of the H2O non-equilibrium radiation model used for water vapor altitude distribution retrieval from the MLT radiation measurements. Our model accounts for 13 excited vibrational states up to energies 7445 cm-1 (the upper levels are 002, 101, 200) [Feofilov et al., 2009]. The model takes into account 54 vibrational-translational (V-T) and vibrational-vibrational (V-V) energy exchange processes at collisions of H2O with N2, O2 and O. The 32 ro-vibrational transitions forming 1.4, 1.9, 2.7, 3.2, 4.7 and 6.3 μm water vapor radiation bands are considered. Currently, the rate constants of intermolecular transitions between vibrational levels at collisions with N2 and O2 are known only for the transitions (010-000) and (001,100-020). In our model of H2O vibrational level kinetics [Feofilov et al., 2009], we assumed that for all collisional transitions, at which the bending mode quantum number, v2, increases by 2: H2O(v1,v2,v3) + M = H2O(v1-1,v2+2,v3) + M H2O(v1,v2,v3) + M = H2O(v1,v2+2,v3-1) + M (1) the rate constants are equal to that of the process H2O(001, 100) + M = H2O(020) + M. Based on the analysis of currently available experimental and theoretical data, we have updated k, the rate constant of transitions (002, 101)→021 and (101, 200)→120, and estimated the effect of a new rate on the H2O vibrational levels populations and limb radiation spectra. The "upper limit" of the effect was estimated using the same rate constant k for all processes of type (1), excluding process (001, 100)→020. The H2O vibrational levels populations and limb radiation spectra were calculated using the ALI-ARMS non-LTE code [Kutepov et al. 1998; Feofilov and Kutepov

  2. Communication: Ro-vibrational control of chemical reactivity in H+CH{sub 4}→ H{sub 2}+CH{sub 3} : Full-dimensional quantum dynamics calculations and a sudden model

    SciTech Connect

    Welsch, Ralph Manthe, Uwe

    2014-08-07

    The mode-selective chemistry of the title reaction is studied by full-dimensional quantum dynamics simulation on an accurate ab initio potential energy surface for vanishing total angular momentum. Using a rigorous transition state based approach and multi-configurational time-dependent Hartree wave packet propagation, initial state-selected reaction probabilities for many ro-vibrational states of methane are calculated. The theoretical results are compared with experimental trends seen in reactions of methane. An intuitive interpretation of the ro-vibrational control of the chemical reactivity provided by a sudden model based on the quantum transition state concept is discussed.

  3. Femtosecond laser electronic excitation tagging for aerodynamic and thermodynamic measurements

    NASA Astrophysics Data System (ADS)

    Calvert, Nathan David

    This thesis presents applications of Femtosecond Laser Electronic Excitation Tagging (FLEET) to a variety of aerodynamic and thermodynamic measurements. FLEET tagged line characteristics such as intensity, width and spectral features are investigated in various flow conditions (pressure, temperature, velocity, steadiness, etc.) and environments (gas composition) for both temporally and spatially instantaneous and averaged data. Special attention is drawn to the nature of first and second positive systems of molecular nitrogen and the ramifications on FLEET measurements. Existing laser-based diagnostic techniques are summarized and FLEET is directly compared with Particle Image Velocimetry (PIV) in various low speed flows. Multidimensional velocity, acceleration, vorticity and other flow parameters are extracted in supersonic free jets and within an enclosed in-draft tunnel test section. Probability distribution functions of the mean and standard deviation of critical flow parameters are unveiled by utilizing a Bayesian statistical framework wherein likelihood functions are established from prior and posterior distributions. Advanced image processing techniques based on fuzzy logic are applied to single-shot FLEET images with low signal-to-noise ratio to improve image quality and reduce uncertainty in data processing algorithms. Lastly, FLEET second positive and first negative emission are considered at a wide range of pressures to correct for changes in select rovibrational peak magnitude and shape due to density from which bulk gas temperature may be extracted.

  4. Similarity criteria in vibrationally and electronically excited gases

    NASA Astrophysics Data System (ADS)

    Kustova, E. V.; Mekhonoshina, M. A.

    2016-11-01

    Similarity criteria related to heat conduction and diffusion (Prandtl and Schmidt numbers) are studied in strongly non-equilibrium reacting flows on the basis of the Chapman-Enskog method. A one-temperature flow description is applied to study high-temperature gas mixtures with slow chemical reactions and excited rovibrational and electronic degrees of freedom of molecules and electronic states of atomic species. Essentially non-monotonic dependence of the Prandtl number on the mixture composition is emphasized; the Schmidt numbers vary weakly with temperature and decrease monotonically with increasing molecular molar fraction. For vibrationally non-equilibrium flows, we consider the detailed state-to-state model. In this case the Prandtl number is determined by translational and rotational energies; the Schmidt numbers are introduced for each vibrational state. The developed models are used to study Prandtl and Schmidt numbers in shock heated and supersonic expanding flows of N2/N and O2/O mixtures. Peculiar features of these similarity criteria in strongly non-equilibrium flows are discussed.

  5. Rovibrational constants of the ground state and v8 = 1 state of 13C2HD3 by high-resolution FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Ng, L. L.; Tan, T. L.

    2016-06-01

    The Fourier transform infrared (FTIR) spectrum of the c-type ν8 band of 13C2HD3 was recorded for the first time at a unapodized resolution of 0.0063 cm-1 in the wavenumber region of 830-1000 cm-1. Through the fitting of a total of 1057 assigned infrared transitions using Watson's A-reduced Hamiltonian in the Ir representation, rovibrational constants for the upper state (v8 = 1) up to five quartic centrifugal distortion terms were derived for the first time with a root-mean-square (rms) deviation of 0.00073 cm-1. The band center of ν8 of 13C2HD3 was found to be 913.011021(55) cm-1. Ground state rovibrational constants up to five quartic terms of 13C2HD3 were also determined from a fit of 453 ground state combination-differences from the present infrared measurements with an rms deviation of 0.00072 cm-1 for the first time. The uncertainty of the measured infrared lines was estimated to be ±0.0012 cm-1. From the ground state rotational constants, the inertial defect of 13C2HD3 was calculated to be 0.06973(16) uÅ2, showing the high planarity of the molecule.

  6. The interaction of CCl4 with Ng (Ng = He, Ne, Ar), O2, D2O and ND3: rovibrational energies, spectroscopic constants and theoretical calculations.

    PubMed

    de Oliveira, Rhuiago M; Roncaratti, Luiz F; de Macedo, Luiz Guilherme M; Gargano, Ricardo

    2017-03-01

    This investigation generated rovibrational energies and spectroscopic constants for systems of CCl4 with Ng (Ng = He, Ne, Ar), O2, D2O and ND3 from scattering experimental data, and the results presented are of interest for microwave spectroscopy studies of small halogenated molecules. The rovibrational spectra were obtained through two different approaches (Dunham and DVR) within the improved Lennard Jones (ILJ) model. Spectra were also generated within ordinary Lennard Jones and deviations suggest that the ILJ model should be preferred due to interactions beyond dispersion forces presented in these systems. Data from the literature and additional high level quantum mechanical calculations presented in this work show that these systems should not be considered as van der Waals complexes due to halogen bonding (HB) interactions, and this is especially true for the CCl4-D2O and CCl4-ND3 complexes. The charge displacement from the latter systems are one order of magnitude higher than the values from literature for CCl4 and He, Ne, Ar and O2 systems, and show significant deviations between DFT and Hartree-Fock values not previously reported in the literature.

  7. Ro-vibrational spectrum of H2O-Ne in the ν2 H2O bending region: A combined ab initio and experimental investigation

    NASA Astrophysics Data System (ADS)

    Liu, Xunchen; Hou, Dan; Thomas, Javix; Li, Hui; Xu, Yunjie

    2016-12-01

    High resolution ro-vibrational transitions of the H2O-Ne complex in the ν2 bending region of H2O at 6 μm have been measured using a rapid scan infrared spectrometer based on an external cavity quantum cascade laser and an astigmatic multipass optical cell. To aid the spectral assignment, a four-dimension potential energy surface of H2O-Ne which depends on the intramolecular bending coordinate of the H2O monomer and the three intermolecular vibrational coordinates has been constructed and the rovibrational transitions have been calculated. Three ortho and two para H2O-20Ne bands have been identified from the experimental spectra. Some weaker transitions belonging to H2O-22Ne have also been identified experimentally. Spectroscopic fits have been performed for both the experimental and theoretical transition frequencies using a simple pseudo-diatomic Hamiltonian including both Coriolis coupling and Fermi resonance terms. The experimental and theoretical spectroscopic constants thus obtained have been compared. Further improvements needed in the potential energy surface and the related spectral simulation have been discussed.

  8. A general variational approach for computing rovibrational resonances of polyatomic molecules. Application to the weakly bound H2He+ and H2ṡCO systems

    NASA Astrophysics Data System (ADS)

    Papp, Dóra; Szidarovszky, Tamás; Császár, Attila G.

    2017-09-01

    The quasi-variational quantum chemical protocol and code GENIUSH [E. Mátyus et al., J. Chem. Phys. 130, 134112 (2009) and C. Fábri et al., J. Chem. Phys. 134, 074105 (2011)] has been augmented with the complex absorbing potential (CAP) technique, yielding a method for the determination of rovibrational resonance states. Due to the effective implementation of the CAP technique within GENIUSH, the GENIUSH-CAP code is a powerful tool for the study of important dynamical features of arbitrary-sized molecular systems with arbitrary composition above their first dissociation limit. The GENIUSH-CAP code has been tested and validated on the H2He+ cation: the computed resonance energies and lifetimes are compared to those obtained with a previously developed triatomic rovibrational resonance-computing code, D2FOPI-CCS [T. Szidarovszky and A. G. Császár Mol. Phys. 111, 2131 (2013)], utilizing the complex coordinate scaling method. A unique feature of the GENIUSH-CAP protocol is that it allows the simple implementation of reduced-dimensional dynamical models. To prove this, resonance energies and lifetimes of the H2ṡCO van der Waals complex have been computed utilizing a four-dimensional model (freezing the two monomer stretches), and a related potential energy surface, of the complex.

  9. A new ab initio potential energy surface for the collisional excitation of HCN by para- and ortho-H{sub 2}

    SciTech Connect

    Denis-Alpizar, Otoniel; Kalugina, Yulia; Stoecklin, Thierry; Vera, Mario Hernández; Lique, François

    2013-12-14

    We present a new four-dimensional potential energy surface for the collisional excitation of HCN by H{sub 2}. Ab initio calculations of the HCN–H{sub 2} van der Waals complex, considering both molecules as rigid rotors, were carried out at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12a] level of theory using an augmented correlation-consistent triple zeta (aVTZ) basis set. The equilibrium structure is linear HCN–H{sub 2} with the nitrogen pointing towards H{sub 2} at an intermolecular separation of 7.20 a{sub 0}. The corresponding well depth is −195.20 cm{sup −1}. A secondary minimum of −183.59 cm{sup −1} was found for a T-shape configuration with the H of HCN pointing to the center of mass of H{sub 2}. We also determine the rovibrational energy levels of the HCN–para-H{sub 2} and HCN–ortho-H{sub 2} complexes. The calculated dissociation energies for the para and ortho complexes are 37.79 cm{sup −1} and 60.26 cm{sup −1}, respectively. The calculated ro-vibrational transitions in the HCN–H{sub 2} complex are found to agree by more than 0.5% with the available experimental data, confirming the accuracy of the potential energy surface.

  10. Symmetry-Based Techniques for Qualitative Understanding of Rovibrational Effects in Spherical-Top Molecular Spectra and Dynamics

    NASA Astrophysics Data System (ADS)

    Mitchell, Justin Chadwick

    2011-12-01

    Using light to probe the structure of matter is as natural as opening our eyes. Modern physics and chemistry have turned this art into a rich science, measuring the delicate interactions possible at the molecular level. Perhaps the most commonly used tool in computational spectroscopy is that of matrix diagonalization. While this is invaluable for calculating everything from molecular structure and energy levels to dipole moments and dynamics, the process of numerical diagonalization is an opaque one. This work applies symmetry and semi-classical techniques to elucidate numerical spectral analysis for high-symmetry molecules. Semi-classical techniques, such as the Potential Energy Surfaces, have long been used to help understand molecular vibronic and rovibronic spectra and dynamics. This investigation focuses on newer semi-classical techniques that apply Rotational Energy Surfaces (RES) to rotational energy level clustering effects in high-symmetry molecules. Such clusters exist in rigid rotor molecules as well as deformable spherical tops. This study begins by using the simplicity of rigid symmetric top molecules to clarify the classical-quantum correspondence of RES semi-classical analysis and then extends it to a more precise and complete theory of modern high-resolution spectra. RES analysis is extended to molecules having more complex and higher rank tensorial rotational and rovibrational Hamiltonians than were possible to understand before. Such molecules are shown to produce an extraordinary range of rotational level clusters, corresponding to a panoply of symmetries ranging from C4v to C2 and C1 (no symmetry) with a corresponding range of new angular momentum localization and J-tunneling effects. Using RES topography analysis and the commutation duality relations between symmetry group operators in the lab-frame to those in the body-frame, it is shown how to better describe and catalog complex splittings found in rotational level clusters. Symmetry

  11. Excitation of Molecular Hydrogen in the Orion Bar Photodissociation Region from a Deep Near-infrared IGRINS Spectrum

    NASA Astrophysics Data System (ADS)

    Kaplan, Kyle F.; Dinerstein, Harriet L.; Oh, Heeyoung; Mace, Gregory N.; Kim, Hwihyun; Sokal, Kimberly R.; Pavel, Michael D.; Lee, Sungho; Pak, Soojong; Park, Chan; Sok Oh, Jae; Jaffe, Daniel T.

    2017-04-01

    We present a deep near-infrared spectrum of the Orion Bar Photodissociation Region (PDR) taken with the Immersion Grating INfrared Spectrometer (IGRINS) on the 2.7 m telescope at the McDonald Observatory. IGRINS has high spectral resolution (R˜ {{45,000}}) and instantaneous broad wavelength coverage (1.45-2.45 μm), enabling us to detect 87 emission lines from rovibrationally excited molecular hydrogen (H2) that arise from transitions out of 69 upper rovibration levels of the electronic ground state. These levels cover a large range of rotational and vibrational quantum numbers and excitation energies, making them excellent probes of the excitation mechanisms of H2 and physical conditions within the PDR. The Orion Bar PDR is thought to consist of cooler high density clumps or filaments (T=50{--}250 K, {n}H={10}5{--}{10}7 cm-3) embedded in a warmer lower density medium (T=250{--}1000 K, {n}H={10}4{--}{10}5 cm-3). We fit a grid of constant temperature and density Cloudy models, which recreate the observed H2 level populations well, to constrain the temperature to a range of 600-650 K and the density to {n}H=2.5× {10}3{--}{10}4 cm-3. The best-fit model gives T = 625 K and {n}H=5× {10}3 cm-3. This well-constrained warm temperature is consistent with kinetic temperatures found by other studies for the Orion Bar’s lower density medium. However, the range of densities well fit by the model grid is marginally lower than those reported by other studies. We could be observing lower density gas than the surrounding medium, or perhaps a density-sensitive parameter in our models is not properly estimated.

  12. Effect of CH stretching excitation on the reaction dynamics of F + CHD{sub 3} → DF + CHD{sub 2}

    SciTech Connect

    Yang, Jiayue; Zhang, Dong; Chen, Zhen; Jiang, Bo; Blauert, Florian; Dai, Dongxu; Wu, Guorong E-mail: xmyang@dicp.ac.cn; Zhang, Donghui; Yang, Xueming E-mail: xmyang@dicp.ac.cn

    2015-07-28

    The vibrationally excited reaction of F + CHD{sub 3}(ν{sub 1} = 1) → DF + CHD{sub 2} at a collision energy of 9.0 kcal/mol is investigated using the crossed-beams and time-sliced velocity map imaging techniques. Detailed and quantitative information of the CH stretching excitation effects on the reactivity and dynamics of the title reaction is extracted with the help of an accurate determination of the fraction of the excited CHD{sub 3} reagent in the crossed-beam region. It is found that all vibrational states of the CHD{sub 2} products observed in the ground-state reaction, which mainly involve the excitation of the umbrella mode of the CHD{sub 2} products, are severely suppressed by the CH stretching excitation. However, there are four additional vibrational states of the CHD{sub 2} products appearing in the excited-state reaction which are not presented in the ground-state reaction. These vibrational states either have the CH stretching excitation retained or involve one quantum excitation in the CH stretching and the excitation of the umbrella mode. Including all observed vibrational states, the overall cross section of the excited-state reaction is estimated to be 66.6% of that of the ground-state one. Experimental results also show that when the energy of CH stretching excitation is released during the reaction, it is deposited almost exclusively as the rovibrational energy of the DF products, with little portion in the translational degree of freedom. For vibrational states of the CHD{sub 2} products observed in both ground- and excited-state reactions, the CH stretching excitation greatly suppresses the forward scattered products, causing a noticeable change in the product angular distributions.

  13. Direct non-Born-Oppenheimer variational calculations of all bound vibrational states corresponding to the first rotational excitation of D{sub 2} performed with explicitly correlated all-particle Gaussian functions

    SciTech Connect

    Sharkey, Keeper L.; Kirnosov, Nikita; Adamowicz, Ludwik

    2015-05-07

    Direct variational calculations where the Born-Oppenheimer approximation is not assumed are done for all rovibrational states of the D{sub 2} molecule corresponding to first excited rotational level (the N = 1 states). All-particle explicitly correlated Gaussian basis functions are used in the calculations. The exponential parameters of the Gaussians are optimized with the aid of analytically calculated energy gradient determined with respect to these parameters. The results allow to determine the ortho-para spin isomerization energies as a function of the vibrational quantum number.

  14. RESONANT CAVITY EXCITATION SYSTEM

    DOEpatents

    Baker, W.R.

    1959-08-01

    A cavity excitation circuit is described for rapidly building up and maintaining high-level oscillations in a resonant cavity. The circuit overcomes oscillation buildup slowing effects such as ion locking in the cavity by providing for the selective application of an amplified accelerating drive signal to the main cavity exciting oscillator during oscillation buildup and a direct drive signal to the oscillator thereafter.

  15. Kinetics studies following state-selective laser excitation. Final progress report, March 15, 1984--July 15, 1993

    SciTech Connect

    Keto, J.W.

    1994-04-01

    The objective of this contract was the study of state-to-state, electronic energy transfer reactions relevant to the excited state chemistry observed in discharges. We studied deactivation reactions and excitation transfer in collisions of excited states of xenon and krypton atoms with Ar, Kr, Xe and chlorine. The reactant states were excited selectively in two-photon transitions using tunable u.v. and v.u.v. lasers. Excited states produced by the collision were observed by their fluorescence. Reaction rates were measured by observing the time dependent decay of signals from reactant and product channels. In addition we measured interaction potentials of the reactants by laser spectroscopy where the laser induced fluorescence or ionization is measured as a function of laser wavelength (excitation spectra) or by measuring fluorescence spectra at fixed laser frequencies with monochromators. The spectra were obtained in the form of either lineshapes or individual lines from rovibrational transitions of bound states. Our research then required several categories of experiments in order to fully understand a reaction process: 1. High resolution laser spectroscopy of bound molecules or lineshapes of colliding pairs is used to determine potential curves for reactants. 2. Direct measurements of state-to-state reaction rates were measured by studying the time dependent loss of excited reactants and the time dependent formation of products. 3. The energy selectivity of a laser can be used to excite reactants on an excited surface with controlled internuclear configurations. For free states of reactants (as exist in a gas cell) this has been termed laser assisted reactions, while for initially bound states (as chemically bound reactants or dimers formed in supersonic beams) the experiments have been termed photo-fragmentation spectroscopy.

  16. 8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER No. 2., AND GENERATOR UNITS BEHIND EXCITER No. 2 IN BACKGROUND. EXCITER No. 1 GENERATOR HAS A COVER OVER TOP HALF OF COMMUTATOR ELEMENT. VIEW TO NORTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  17. Electron Scattering from NO: Cross Sections and their Implication to NO Excitation Processes Under Auroral Conditions

    NASA Astrophysics Data System (ADS)

    Brunger, M. J.

    1998-10-01

    We present a selection of our results for differential and integral cross section measurements of elastic, rovibrational (0 arrow 1, 2, 3, 4) and electronic-state excitation in NO by electron impact. The energy range of the present measurements was 7.5 - 50 eV. In general these measurements are often the only available data in the literature. However, where possible we compare the current results with those of other experimental groups and with theoretical calculations(L.E. Machado, A.L. Monzani, M-T. Lee and M.M. Fujimoto in ``Proc. Int. Sym. El- and Ph- Mol. Coll. and Swarms'', H32, 1995; and private communication.). A subset of these new electron impact cross sections was combined with a measured(P.D. Feldman and J.P. Doering, J. Geophys. Res. 80), 2808-2812, 1975. IBC auroral secondary electron distribution and the electronic-vibrational populations were determined for conditions of statistical equilibrium. The model(D.C. Cartwright, J. Geophys. Res. 83), 517-531, 1978. of statistical equilibrium determines the density of each excited state from the balance between population by electron impact excitation and radiative cascade, and depopulation by radiative cascade and quenching by N_2, O2 and O. Results of this analysis will also be presented at the meeting.

  18. Rovibrational energy transfer in the 4nuCH manifold of acetylene, viewed by IR-UV double resonance spectroscopy. 5. Detailed kinetic model.

    PubMed

    Payne, Mark A; Milce, Angela P; Frost, Michael J; Orr, Brian J

    2007-12-13

    Time-resolved infrared-ultraviolet double resonance (IR-UV DR) spectroscopy provides a distinctive way to examine collision-induced state-to-state energy transfer between rotational J-levels in vibrational manifolds of small polyatomic molecules, such as acetylene (C2H2) in its electronic ground state X. We consider the 4nuCH rovibrational manifold of C2H2 at approximately 12,700 cm(-1), where the principal source of IR-brightness is the (nu1+3nu3) or (1 0 3 0 0)0 Sigma+u vibrational combination level. In this highly congested manifold, anharmonic, l-resonance, and Coriolis couplings affect the J-levels of interest, implicating them in a complicated variety of intramolecular dynamics. Previous papers of this series have reported several seemingly anomalous J-resolved phenomena induced by collisions in C2H2 gas at room temperature with pressures and IR-UV pump-probe delay intervals corresponding to remarkably high Lennard-Jones collisional efficiencies P: odd-DeltaJ rotational energy transfer (10(-3)rovibrational "gateway" channels, such as via (nu1+3nu3) Sigma+u J=12 (with P as high as approximately 0.1); an apparently ubiquitous collision-induced quasi-continuous background (10(-3)rovibrational levels in an IR-bright manifold V and a quasi-continuous bath B, mediated by a J-specific gateway manifold G.

  19. Excitability dependent pattern formation

    NASA Astrophysics Data System (ADS)

    Prabhakara, Kaumudi; Gholami, Azam; Bodenschatz, Eberhard

    2014-03-01

    On starvation, the amoebae Dictyostelium discoideum emit the chemo-attractant cyclic adenosine monophosphate (cAMP) at specific frequencies. The neighboring amoebae sense cAMP through membrane receptors and produce their own cAMP. Soon the cells synchronize and move via chemotaxis along the gradient of cAMP. The response of the amoebae to the emission of cAMP is seen as spiral waves or target patterns under a dark field microscope. The causal reasons for the selection of one or the other patterns are still unclear. Here we present a possible explanation based on excitability. The excitability of the amoebae depends on the starvation time because the gene expression changes with starvation. Cells starved for longer times are more excitable. In this work, we mix cells of different excitabilities to study the dependence of the emergent patterns on the excitability. Preliminary results show a transition from spirals to target patterns for specific excitabilities. A phase map of the patterns for different combinations of excitability and number densities is obtained. We compare our findings with numerical simulations of existing theoretical models.

  20. A quantum-rovibrational-state-selected study of the reaction in the collision energy range of 0.05-10.00 eV: translational, rotational, and vibrational energy effects.

    PubMed

    Xu, Yuntao; Xiong, Bo; Chang, Yih-Chung; Pan, Yi; Lo, Po Kam; Lau, Kai Chung; Ng, C Y

    2017-03-29

    We report detailed absolute integral cross sections (σ's) for the quantum-rovibrational-state-selected ion-molecule reaction in the center-of-mass collision energy (Ecm) range of 0.05-10.00 eV, where (vvv) = (000), (100), and (020), and . Three product channels, HCO(+) + OH, HOCO(+) + H, and CO(+) + H2O, are identified. The measured σ(HCO(+)) curve [σ(HCO(+)) versus Ecm plot] supports the hypothesis that the formation of the HCO(+) + OH channel follows an exothermic pathway with no potential energy barriers. Although the HOCO(+) + H channel is the most exothermic, the σ(HOCO(+)) is found to be significantly lower than the σ(HCO(+)). The σ(HOCO(+)) curve is bimodal, indicating two distinct mechanisms for the formation of HOCO(+). The σ(HOCO(+)) is strongly inhibited at Ecm < 0.4 eV, but is enhanced at Ecm > 0.4 eV by (100) vibrational excitation. The Ecm onsets of σ(CO(+)) determined for the (000) and (100) vibrational states are in excellent agreement with the known thermochemical thresholds. This observation, along with the comparison of the σ(CO(+)) curves for the (100) and (000) states, shows that kinetic and vibrational energies are equally effective in promoting the CO(+) channel. We have also performed high-level ab initio quantum calculations on the potential energy surface, intermediates, and transition state structures for the titled reaction. The calculations reveal potential barriers of ≈0.5-0.6 eV for the formation of HOCO(+), and thus account for the low σ(HOCO(+)) and its bimodal profile observed. The Ecm enhancement for σ(HOCO(+)) at Ecm ≈ 0.5-5.0 eV can be attributed to the direct collision mechanism, whereas the formation of HOCO(+) at low Ecm < 0.4 eV may involve a complex mechanism, which is mediated by the formation of a loosely sticking complex between HCO(+) and OH. The direct collision and complex mechanisms proposed also allow the rationalization of the vibrational inhibition at low Ecm and the vibrational enhancement at high

  1. 15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. 1 BEHIND. OVERHEAD CRANE DANGLES AT TOP OF PHOTO. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  2. Developmant of a Reparametrized Semi-Empirical Force Field to Compute the Rovibrational Structure of Large PAHs

    NASA Astrophysics Data System (ADS)

    Fortenberry, Ryan

    energy surface. QFFs can regularly predict the fundamental vibrational frequencies to within 5 cm-1 of experimentally measured values. This level of accuracy represents a reduction in discrepancies by an order of magnitude compared with harmonic frequencies calculated with density functional theory (DFT). The major limitation of the QFF strategy is that the level of electronic-structure theory required to develop a predictive force field is prohibitively time consuming for molecular systems larger than 5 atoms. Recent advances in QFF techniques utilizing informed DFT approaches have pushed the size of the systems studied up to 24 heavy atoms, but relevant PAHs can have up to hundreds of atoms. We have developed alternative electronic-structure methods that maintain the accuracy of the coupled-cluster calculations extrapolated to the complete basis set limit with relativistic and core correlation corrections applied: the CcCR QFF. These alternative methods are based on simplifications of Hartree—Fock theory in which the computationally intensive two-electron integrals are approximated using empirical parameters. These methods reduce computational time to orders of magnitude less than the CcCR calculations. We have derived a set of optimized empirical parameters to minimize the difference molecular ions of astrochemical significance. We have shown that it is possible to derive a set of empirical parameters that will produce RMS energy differences of less than 2 cm- 1 for our test systems. We are proposing to adopt this reparameterization strategy and some of the lessons learned from the informed DFT studies to create a semi-empirical method whose tremendous speed will allow us to study the rovibrational structure of large PAHs with up to 100s of carbon atoms.

  3. Timing of cortical excitability changes during the reaction time of movements superimposed on tonic motor activity.

    PubMed

    Schneider, Cyril; Lavoie, Brigitte A; Barbeau, Hugues; Capaday, Charles

    2004-12-01

    Seated subjects were instructed to react to an auditory cue by simultaneously contracting the tibialis anterior (TA) muscle of each ankle isometrically. Focal transcranial magnetic stimulation of the leg area of the motor cortex (MCx) was used to determine the time course of changes in motor-evoked potential amplitude (MEP) during the reaction time (RT). In one condition the voluntary contraction was superimposed on tonic EMG activity maintained at 10% of maximal voluntary contraction. In the other condition the voluntary contraction was made starting from rest. MEPs in the TA contralateral to the stimulation coil were evoked at various times during the RT in each condition. These were compared to the control MEPs evoked during tonic voluntary activity or with the subject at rest. The RT was measured trial by trial from the EMG activity of the TA ipsilateral to the magnetic stimulus, taking into account the nearly constant time difference between the two sides. The MEPs became far greater than control MEPs during the RT (mean = 332%, SD = 44 %, of control MEPs, P < 0.001) without any measurable change in the background level of EMG activity. The onset of this facilitation occurred on average 12.80 ms (SD = 7.55 ms) before the RT. There was no difference in the onset of facilitation between the two conditions. Because MEPs were facilitated without a change in the background EMG activity, it is concluded that this facilitation is specifically due to an increase of MCx excitability just before voluntary muscle activation. This conclusion is further reinforced by the observation that MEPs evoked by near-threshold anodal stimuli to the MCx were not facilitated during the RT, in contrast to those evoked by near-threshold transcranial magnetic stimulation. However, several observations in the present and previous studies indicate that MEP amplitude may be more sensitive to alpha-motoneuron activity than to motor cortical neuron activity, an idea that has important

  4. Geomagnetic excitation of nutation

    NASA Astrophysics Data System (ADS)

    Ron, C.; Vondrák, J.

    2015-08-01

    We tested the hypothesis of Malkin (2013), who demonstrated that the observed changes of Free Core Nutation parameters (phase, amplitude) occur near the epochs of geomagnetic jerks. We found that if the numerical integration of Brzeziński broad-band Liouville equations of atmospheric/oceanic excitations is re-initialized at the epochs of geomagnetic jerks, the agreement between the integrated and observed celestial pole offsets is improved (Vondrák & Ron, 2014). Nevertheless, this approach assumes that the influence of geomagnetic jerks leads to a stepwise change in the position of celestial pole, which is physically not acceptable. Therefore we introduce a simple continuous excitation function that hypothetically describes the influence of geomagnetic jerks, and leads to rapid but continuous changes of pole position. The results of numerical integration of atmospheric/oceanic excitations and this newly introduced excitation are then compared with the observed celestial pole offsets, and prove that the agreement is improved significantly.

  5. Ab initio effective rotational and rovibrational Hamiltonians for non-rigid systems via curvilinear second order vibrational Møller-Plesset perturbation theory

    NASA Astrophysics Data System (ADS)

    Changala, P. Bryan; Baraban, Joshua H.

    2016-11-01

    We present a perturbative method for ab initio calculations of rotational and rovibrational effective Hamiltonians of both rigid and non-rigid molecules. Our approach is based on a curvilinear implementation of second order vibrational Møller-Plesset perturbation theory extended to include rotational effects via a second order contact transformation. Though more expensive, this approach is significantly more accurate than standard second order vibrational perturbation theory for systems that are poorly described to zeroth order by rectilinear normal mode harmonic oscillators. We apply this method to and demonstrate its accuracy on two molecules: Si2C, a quasilinear triatomic with significant bending anharmonicity, and CH3NO2, which contains a completely unhindered methyl rotor. In addition to these two examples, we discuss several key technical aspects of the method, including an efficient implementation of Eckart and quasi-Eckart frame embedding that does not rely on numerical finite differences.

  6. Ab initio effective rotational and rovibrational Hamiltonians for non-rigid systems via curvilinear second order vibrational Møller-Plesset perturbation theory.

    PubMed

    Changala, P Bryan; Baraban, Joshua H

    2016-11-07

    We present a perturbative method for ab initio calculations of rotational and rovibrational effective Hamiltonians of both rigid and non-rigid molecules. Our approach is based on a curvilinear implementation of second order vibrational Møller-Plesset perturbation theory extended to include rotational effects via a second order contact transformation. Though more expensive, this approach is significantly more accurate than standard second order vibrational perturbation theory for systems that are poorly described to zeroth order by rectilinear normal mode harmonic oscillators. We apply this method to and demonstrate its accuracy on two molecules: Si2C, a quasilinear triatomic with significant bending anharmonicity, and CH3NO2, which contains a completely unhindered methyl rotor. In addition to these two examples, we discuss several key technical aspects of the method, including an efficient implementation of Eckart and quasi-Eckart frame embedding that does not rely on numerical finite differences.

  7. Ab initio ro-vibrational Hamiltonian in irreducible tensor formalism: a method for computing energy levels from potential energy surfaces for symmetric-top molecules

    NASA Astrophysics Data System (ADS)

    Rey, M.; Nikitin, A. V.; Tyuterev, Vl. G.

    2010-08-01

    A theoretical approach to study ro-vibrational molecular states from a full nuclear Hamiltonian expressed in terms of normal-mode irreducible tensor operators is presented for the first time. Each term of the Hamiltonian expansion can thus be cast in the tensor form in a systematic way using the formalism of ladder operators. Pyramidal XY3 molecules appear to be good candidates to validate this approach which allows taking advantage of the symmetry properties when doubly degenerate vibrational modes are considered. Examples of applications will be given for PH3 where variational calculations have been carried out from our recent potential energy surface [Nikitin et al., J. Chem. Phys. 130, 244312 (2009)].

  8. Using monomer vibrational wavefunctions as contracted basis functions to compute rovibrational levels of an H2O-atom complex in full dimensionality.

    PubMed

    Wang, Xiao-Gang; Carrington, Tucker

    2017-03-14

    In this paper, we present new ideas for computing rovibrational energy levels of molecules composed of two components and apply them to H2O-Cl(-). When both components are themselves molecules, Euler angles that specify their orientation with respect to an axis system attached to the inter-monomer vector are used as vibrational coordinates. For H2O-Cl(-), there is only one set of Euler angles. Using Euler angles as intermolecular vibrational coordinates is advantageous because in many cases coupling between them and coordinates that describe the shape of the monomers is unimportant. The monomers are not assumed to be rigid. In the most efficient calculation, vibrational wavefunctions of the monomers are used as contracted basis functions. Energy levels are calculated using the Lanczos algorithm.

  9. 4-Component correlated all-electron study on Eka-actinium Fluoride (E121F) including Gaunt interaction: Accurate analytical form, bonding and influence on rovibrational spectra

    NASA Astrophysics Data System (ADS)

    Amador, Davi H. T.; de Oliveira, Heibbe C. B.; Sambrano, Julio R.; Gargano, Ricardo; de Macedo, Luiz Guilherme M.

    2016-10-01

    A prolapse-free basis set for Eka-Actinium (E121, Z = 121), numerical atomic calculations on E121, spectroscopic constants and accurate analytical form for the potential energy curve of diatomic E121F obtained at 4-component all-electron CCSD(T) level including Gaunt interaction are presented. The results show a strong and polarized bond (≈181 kcal/mol in strength) between E121 and F, the outermost frontier molecular orbitals from E121F should be fairly similar to the ones from AcF and there is no evidence of break of periodic trends. Moreover, the Gaunt interaction, although small, is expected to influence considerably the overall rovibrational spectra.

  10. Using monomer vibrational wavefunctions as contracted basis functions to compute rovibrational levels of an H2O-atom complex in full dimensionality

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Carrington, Tucker

    2017-03-01

    In this paper, we present new ideas for computing rovibrational energy levels of molecules composed of two components and apply them to H2O-Cl-. When both components are themselves molecules, Euler angles that specify their orientation with respect to an axis system attached to the inter-monomer vector are used as vibrational coordinates. For H2O-Cl-, there is only one set of Euler angles. Using Euler angles as intermolecular vibrational coordinates is advantageous because in many cases coupling between them and coordinates that describe the shape of the monomers is unimportant. The monomers are not assumed to be rigid. In the most efficient calculation, vibrational wavefunctions of the monomers are used as contracted basis functions. Energy levels are calculated using the Lanczos algorithm.

  11. Leading order nonadiabatic corrections to rovibrational levels of H{sub 2}, D{sub 2}, and T{sub 2}

    SciTech Connect

    Pachucki, Krzysztof; Komasa, Jacek

    2015-07-21

    An efficient computational approach to nonadiabatic effects in the hydrogen molecule (H{sub 2}, D{sub 2}, and T{sub 2}) is presented. The electronic wave function is expanded in the James-Coolidge basis set, which enables obtaining a very high accuracy of nonadiabatic potentials. A single point convergence of the potentials with growing size of the basis set reveals a relative accuracy ranging from 10{sup −8} to 10{sup −13}. An estimated accuracy of the leading nonadiabatic correction to the rovibrational energy levels is of the order of 10{sup −7} cm{sup −1}. After a significant increase in the accuracy of the Born-Oppenheimer and adiabatic calculations, the nonadiabatic results presented in this report constitute another step towards highly accurate theoretical description of the hydrogen molecule.

  12. Excitation by rockets

    NASA Technical Reports Server (NTRS)

    Tammadge, C. E.

    1975-01-01

    Standard methods of excitation are not always practical when a single mode of known frequency requires investigation. This form of investigation is often required on a modified aircraft. A new method of excitation was developed and proved in flight, which consists of firing small rocket charges attached to the aircraft structure. Damping values at gradually increasing airspeeds are obtained, as in Stick Jerk tests, and flutter speeds predicted.

  13. Effect of updated relaxation rate constants on the H2O vibrational level populations and ro-vibrational spectra in the mesosphere and lower thermosphere

    NASA Astrophysics Data System (ADS)

    Manuilova, R. O.; Feofilov, A. G.; Kutepov, A. A.; Yankovsky, V. A.

    2015-11-01

    This paper discusses the formation mechanisms of infrared radiation in H2O ro-vibrational bands in the mesosphere and lower thermosphere (MLT). At these heights and above, the vibrational levels of the molecules involved in radiative transitions are not in local thermodynamic equilibrium (LTE) with the surrounding medium, and the biggest uncertainty source in modeling the IR radiation in molecular bands is associated with the corresponding vibrational kinetics model parameters. In this study, we re-analyze available experimental data of Barnes et al. (2004) and Zittel and Masturzo (1991) and update the rate constant of V-V exchange (k) corresponding to the second vibrational number v2 increase by two and the first (or the third) quantum number decrease by one. The estimated values of k for quenching by N2 and O2 are 1.7 × 10-12 and 1.3 × 10-12 cm3 s-1, respectively. These values are about four times larger than the values used in all earlier models of non-LTE populations of vibrational levels and IR radiation in ro-vibrational bands of H2O. We state that using the same k for all processes of vibrational-vibrational energy exchange does not correspond to laboratory experiments and can lead to offsets both in calculating the vibrational level populations and in H2O concentration retrievals from IR spectral radiance. We provide the estimates of these offsets as well as a list of spectral microwindows, in which H2O radiance is sensitive to uncertainty of k.

  14. High resolution study of the ν2 and ν5 rovibrational fundamental bands of thionyl chloride: Interplay of an evolutionary algorithm and a line-by-line analysis

    NASA Astrophysics Data System (ADS)

    Roucou, Anthony; Dhont, Guillaume; Cuisset, Arnaud; Martin-Drumel, Marie-Aline; Thorwirth, Sven; Fontanari, Daniele; Meerts, W. Leo

    2017-08-01

    The ν2 and ν5 fundamental bands of thionyl chloride (SOCl2) were measured in the 420 cm-1-550 cm-1 region using the FT-far-IR spectrometer exploiting synchrotron radiation on the AILES beamline at SOLEIL. A straightforward line-by-line analysis is complicated by the high congestion of the spectrum due to both the high density of SOCl2 rovibrational bands and the presence of the ν2 fundamental band of sulfur dioxide produced by hydrolysis of SOCl2 with residual water. To overcome this difficulty, our assignment procedure for the main isotopologues 32S16O35Cl2 and 32S16O35Cl37Cl alternates between a direct fit of the spectrum, via a global optimization technique, and a traditional line-by-line analysis. The global optimization, based on an evolutionary algorithm, produces rotational constants and band centers that serve as useful starting values for the subsequent spectroscopic analysis. This work helped to identify the pure rotational submillimeter spectrum of 32S16O35Cl2 in the v2=1 and v5=1 vibrational states of Martin-Drumel et al. [J. Chem. Phys. 144, 084305 (2016)]. As a by-product, the rotational transitions of the v4=1 far-IR inactive state were identified in the submillimeter spectrum. A global fit gathering all the microwave, submillimeter, and far-IR data of thionyl chloride has been performed, showing that no major perturbation of rovibrational energy levels occurs for the main isotopologue of the molecule.

  15. Non-LTE Effects on the H3+ Rovibrational Population in the Jovian Ionsophere rK Planets: Jupiter, Ionosphere: Modeling

    NASA Astrophysics Data System (ADS)

    Kim, Yong Ha

    2012-04-01

    We investigate non-LTE effects on the hrp\\ level populations to help the analysis of the observed 2 and 3.5 micron hrp\\ emissions from the Jovian ionosphere. We begin by constructing a simple three-level model, in order to compute the intensity ratio of the R(3,4) line in the hot band to the Q(1,0) line in the fundamental band, which have been observed in the Jovian auroral regions. We find that non-LTE effects produce only small changes in the intensity ratios for ambient hto\\ densities less than or equal to 5×1011 cm-3. We then construct two comprehensive models by including all the collisional and radiative transitions between pairs of more than a thousand known hrp\\ rovibrational levels with energies less than 10000 cm-1. By employing these models, we find that the intensity ratios of the lines in the hot and fundamental bands are affected greatly by non-LTE effects, but the details depend sensitively on the number of collisional and radiative transitions included in the models. Non-LTE effects on the rovibrational population become evident at about the same ambient hto\\ densities in the comprehensive models as in the three-level model. However, the models show that rotational temperatures derived from the intensities of rotational lines in the ν_2 and 2ν_2 bands may differ significantly from the ambient temperatures in the non-LTE regime. We find that significant non-LTE effects appear near and above the hrp\\ peak, and that the kinetic temperatures in the Jovian thermospheric temperatures derived from the observed line ratios in the 2 and 3.5 micron hrp\\ emissions are highly model dependent.

  16. ROVIBRATIONALLY RESOLVED DIRECT PHOTODISSOCIATION THROUGH THE LYMAN AND WERNER TRANSITIONS OF H{sub 2} FOR FUV/X-RAY-IRRADIATED ENVIRONMENTS

    SciTech Connect

    Gay, C. D.; Porter, R. L.; Stancil, P. C.; Abel, N. P.; Ferland, G. J.; Shaw, G.; Van Hoof, P. A. M.; Williams, R. J. R. E-mail: ryanlporter@gmail.com E-mail: npabel2@gmail.com E-mail: gargishaw@gmail.com E-mail: robin.williams@awe.co.uk

    2012-02-10

    Using ab initio potential curves and dipole transition moments, cross-section calculations were performed for the direct continuum photodissociation of H{sub 2} through the B{sup 1}{Sigma}{sup +}{sub u} <- X{sup 1}{Sigma}{sup +}{sub g} (Lyman) and C{sup 1}{Pi}{sub u} <- X{sup 1}{Sigma}{sup +}{sub g} (Werner) transitions. Partial cross-sections were obtained for wavelengths from 100 A to the dissociation threshold between the upper electronic state and each of the 301 bound rovibrational levels v''J'' within the ground electronic state. The resulting cross-sections are incorporated into three representative classes of interstellar gas models: diffuse clouds, photon-dominated regions, and X-ray-dominated regions (XDRs). The models, which used the CLOUDY plasma/molecular spectra simulation code, demonstrate that direct photodissociation is comparable to fluorescent dissociation (or spontaneous radiative dissociation, the Solomon process) as an H{sub 2} destruction mechanism in intense far-ultraviolet or X-ray-irradiated gas. In particular, changes in H{sub 2} rotational column densities are found to be as large as 20% in the XDR model with the inclusion of direct photodissociation. The photodestruction rate from some high-lying rovibrational levels can be enhanced by pumping from H Ly{beta} due to a wavelength coincidence with cross-section resonances resulting from quasi-bound levels of the upper electronic states. Given the relatively large size of the photodissociation data set, a strategy is described to create truncated, but reliable, cross-section data consistent with the wavelength resolving power of typical observations.

  17. A semi-classical approach to the calculation of highly excited rotational energies for asymmetric-top molecules

    PubMed Central

    Schmiedt, Hanno; Schlemmer, Stephan; Yurchenko, Sergey N.; Yachmenev, Andrey

    2017-01-01

    We report a new semi-classical method to compute highly excited rotational energy levels of an asymmetric-top molecule. The method forgoes the idea of a full quantum mechanical treatment of the ro-vibrational motion of the molecule. Instead, it employs a semi-classical Green's function approach to describe the rotational motion, while retaining a quantum mechanical description of the vibrations. Similar approaches have existed for some time, but the method proposed here has two novel features. First, inspired by the path integral method, periodic orbits in the phase space and tunneling paths are naturally obtained by means of molecular symmetry analysis. Second, the rigorous variational method is employed for the first time to describe the molecular vibrations. In addition, we present a new robust approach to generating rotational energy surfaces for vibrationally excited states; this is done in a fully quantum-mechanical, variational manner. The semi-classical approach of the present work is applied to calculating the energies of very highly excited rotational states and it reduces dramatically the computing time as well as the storage and memory requirements when compared to the fullly quantum-mechanical variational approach. Test calculations for excited states of SO2 yield semi-classical energies in very good agreement with the available experimental data and the results of fully quantum-mechanical calculations. PMID:28000807

  18. A semi-classical approach to the calculation of highly excited rotational energies for asymmetric-top molecules.

    PubMed

    Schmiedt, Hanno; Schlemmer, Stephan; Yurchenko, Sergey N; Yachmenev, Andrey; Jensen, Per

    2017-01-18

    We report a new semi-classical method to compute highly excited rotational energy levels of an asymmetric-top molecule. The method forgoes the idea of a full quantum mechanical treatment of the ro-vibrational motion of the molecule. Instead, it employs a semi-classical Green's function approach to describe the rotational motion, while retaining a quantum mechanical description of the vibrations. Similar approaches have existed for some time, but the method proposed here has two novel features. First, inspired by the path integral method, periodic orbits in the phase space and tunneling paths are naturally obtained by means of molecular symmetry analysis. Second, the rigorous variational method is employed for the first time to describe the molecular vibrations. In addition, we present a new robust approach to generating rotational energy surfaces for vibrationally excited states; this is done in a fully quantum-mechanical, variational manner. The semi-classical approach of the present work is applied to calculating the energies of very highly excited rotational states and it reduces dramatically the computing time as well as the storage and memory requirements when compared to the fullly quantum-mechanical variational approach. Test calculations for excited states of SO2 yield semi-classical energies in very good agreement with the available experimental data and the results of fully quantum-mechanical calculations.

  19. Systematic Study of Two-Pion Production in NN Collisions--from Single-Baryon to Di-Baryon Excitations

    SciTech Connect

    Skorodko, T.; Bashkanov, M.; Clement, H.; Doroshkevich, E.; Khakimova, O.; Kren, F.; Pricking, A.; Wagner, G. J.

    2010-08-05

    The two-pion production in nucleon-nucleon collisions has been studied by exclusive and kinematically complete experiments from threshold up to T{sub p} = 1.36 GeV at CELSIUS-WASA. At near-threshold energies the total and differential distributions for the {pi}{sup +{pi}-} and {pi}{sup 0{pi}0} channels are dominated by Roper excitation and its decay into N{sigma}s and {Delta}{pi} channels. At beam energies T{sub p}>1.1 GeV the {Delta}{Delta} excitation governs the two-pion production process. In the {pi}{sup +{pi}+} channel evidence is found for the excitation of a higher-lying I =3/2 resonance, favorably the {Delta}(1600). The isovector fusion processes leading to the deuteron and to quasi-stable {sup 2}He, respectively, exhibit no or only a modest ABC-effect, i.e. low-mass enhancement in the {pi}{pi}-invariant mass spectrum, and can be described by conventional t-channel {Delta}{Delta} excitation. On the other hand, the isoscalar fusion process to the deuteron exhibits a dramatic ABC-effect correlated with a narrow resonance-like energy dependence in the total cross section with a width of only 50 MeV and situated at a mass 90 MeV below the {Delta}{Delta} mass.

  20. Investigation of Nonequilibrium Effects in Axisymmetric Nozzle and Blunt Body Nitrogen Flows by Means of a Reduced Rovibrational Collisional Model

    DTIC Science & Technology

    2011-12-21

    for N +N2 inelastic collisions are computed based on the hypothesis of equilibrium between translational and rotational modes. Inelastic N2 +N2...dissociation and excitation. Vibrationally averaged rate coefficients for N + N2 inelastic collisions are computed based on the hypothesis of equilibrium ...their own temperatures and are valid only in case of small departure from equilibrium [2], since the details of energy level dynamics are not taken

  1. Excitation Methods for Bridge Structures

    SciTech Connect

    Farrar, C.R.; Duffy, T.A.; Cornwell, P.J.; Doebling, S.W.

    1999-02-08

    This paper summarizes the various methods that have been used to excited bridge structures during dynamic testing. The excitation methods fall into the general categories of ambient excitation methods and measured-input excitation methods. During ambient excitation the input to the bridge is not directly measured. In contrast, as the category label implies, measured-input excitations are usually applied at a single location where the force input to the structure can be monitored. Issues associated with using these various types of measurements are discussed along with a general description of the various excitation methods.

  2. Autoionization study of the Argon 2p satellites excited near the argon 2s threshold

    SciTech Connect

    Wang, H.; Glans, P.; Hemmers, O.

    1997-04-01

    The dynamics of near-threshold photoionization is a complex phenomenon in which the many-electron character of the wavefunctions plays an important role. According to generalized time-independent resonant scattering theory, the transition matrix element from an initial state to a final state is the summation of the amplitudes of direct photoionization and an indirect term in which intermediate states are involved and the resonant behavior is embedded. Studies of the interference effects of intermediate states have been explored in the cases where the direct term is negligible. In the present work, electron time-of-flight spectra of the Ar 2p satellites were measured at two angles (magic and 0{degrees}) in the dipole plane with the exciting photon energy tuned in the vicinity of the Ar 2s threshold. For excitation far below or above the 2s threshold, the 2p satellites spectrum is dominated by 3p to np shakeup contributions upon the ionization of a 2p electron.

  3. Spin waves and magnetic excitations

    SciTech Connect

    Borovik-Romanov, A.S.; Sinha, S.K.

    1988-01-01

    This book describes both simple spin waves (magnons) and complicated excitations in magnetic systems. The following subjects are covered: - various methods of magnetic excitation investigations such as neutron scattering on magnetic excitations, spin-wave excitation by radio-frequency, power light scattering on magnons and magnetic excitation observation within the light-absorption spectrum; - oscillations of magnetic electron systems coupled with phonons, nuclear spin systems and localized impurity modes: - low-dimensional magnetics, amorphous magnetics and spin glasses.

  4. Positron excitation of neon

    NASA Technical Reports Server (NTRS)

    Parcell, L. A.; Mceachran, R. P.; Stauffer, A. D.

    1990-01-01

    The differential and total cross section for the excitation of the 3s1P10 and 3p1P1 states of neon by positron impact were calculated using a distorted-wave approximation. The results agree well with experimental conclusions.

  5. Proteins of Excitable Membranes

    PubMed Central

    Nachmansohn, David

    1969-01-01

    Excitable membranes have the special ability of changing rapidly and reversibly their permeability to ions, thereby controlling the ion movements that carry the electric currents propagating nerve impulses. Acetylcholine (ACh) is the specific signal which is released by excitation and is recognized by a specific protein, the ACh-receptor; it induces a conformational change, triggering off a sequence of reactions resulting in increased permeability. The hydrolysis of ACh by ACh-esterase restores the barrier to ions. The enzymes hydrolyzing and forming ACh and the receptor protein are present in the various types of excitable membranes. Properties of the two proteins directly associated with electrical activity, receptor and esterase, will be described in this and subsequent lectures. ACh-esterase has been shown to be located within the excitable membranes. Potent enzyme inhibitors block electrical activity demonstrating the essential role in this function. The enzyme has been recently crystallized and some protein properties will be described. The monocellular electroplax preparation offers a uniquely favorable material for analyzing the properties of the ACh-receptor and its relation to function. The essential role of the receptor in electrical activity has been demonstrated with specific receptor inhibitors. Recent data show the basically similar role of ACh in the axonal and junctional membranes; the differences of electrical events and pharmacological actions are due to variations of shape, structural organization, and environment. PMID:19873642

  6. Rovibrational spectra of ammonia. II. Detailed analysis, comparison, and prediction of spectroscopic assignments for 14NH3, 15NH3, and 14ND3.

    PubMed

    Huang, Xinchuan; Schwenke, David W; Lee, Timothy J

    2011-01-28

    Several aspects of ammonia rovibrational spectra have been investigated using the new HSL-2 potential energy surface that includes an approximate correction for nonadiabatic effects. The unprecedented accuracy of rovibrational energy levels and transition energies computed using HSL-2 was demonstrated in Part I of this study. For (14)NH(3), new assignments for a few ν(3) + ν(4) band transitions and energy levels are suggested, and discrepancies between computed and HITRAN energy levels in the 2ν(4) band are analyzed (2ν(4) is the most difficult band below 5000 cm(-1)). New assignments are suggested for existing or missing 2ν(4) levels. Several new vibrational bands are identified from existing, unassigned HITRAN data, including 2ν(2) + ν(4), (ν(3) + ν(4)) -A(')∕A("), ν(1) + 2ν(2), and 2ν(2) + 2ν(4). The strong mixing between the 2ν(4) and 2ν(2) + ν(4) bands is carefully examined and found to be the source of the difficulties in the experimental modeling of 2ν(4). Discussion is presented for preliminary J = 10 results, where the overall root-mean-square error is estimated to be less than 0.039 cm(-1). The analysis of the 4ν(2) band demonstrates both the reliability and the accuracy of predictions from HSL-2. The full list of computed J = 0 band origins (with assignments) and the inversion splittings up to 7000-8000 cm(-1) above the zero-point energy are presented. J = 0-2 levels are reported for those bands below 5100 cm(-1) that are missing from the HITRAN database. For (15)NH(3), excellent agreement is found for the available ν(2) and ν(3) + ν(4)(E) transition energies, but significant deficiencies are shown for HITRAN levels and several corrections are suggested. The (15)N isotopic effects are presented for the J = 0-6 levels of 13 HITRAN bands. For (14)ND(3), we reproduce the pure rotational inversion spectra line frequencies with an accuracy similar to that for (14)NH(3). However, it is not possible to reproduce simultaneously all four

  7. Photogeneration of, and Efficient Collisional Energy Transfer from, Vibrationally Excited Hydrogen Isocyanide (hnc)

    NASA Astrophysics Data System (ADS)

    Wilhelm, Michael J.; Dai, Hai-Lung

    2013-06-01

    Time-resolved IR emission spectroscopy has previously been used to characterize the 193 nm photodissociation dynamics of vinyl cyanide, H_{2}CC(H)CN. Of significance, it was observed that the major molecular elimination channels generated ro-vibrationally excited photofragments consisting of: HCN + H_{2}CC: and HNC + HCCH, for which the HCN / HNC branching ratio was deduced to be 3.3 to 1. In the present study, we examine the collisional deactivation of the vibrationally excited (E_{vib}=15 kcal mole^{-1} above the zero-point energy) ν_{1} NH and ν_{3} NC stretches of HNC, in response to collisions with a series of inert rare-gas atoms: Rg=He, Ar, Kr, and Xe. Spectral modeling of the IR emission allows direct determination of the time-dependent average internal energy of HNC, and therefore a quantification of the average energy lost per collision, as a function of the internal energy. Similar to vibrationally excited radicals, collisional deactivation of HNC is shown to be remarkably efficient, likely due to comparatively strong HNC / Rg intermolecular attractive interactions. Subsequently, depending upon the relative rates, excited HNC can either isomerize to the energetically more stable HCN, or be rapidly quenched and kinetically trapped as HNC. Potential implications for the astrophysical HNC / HCN abundance ratio problem will be discussed. M. J. Wilhelm, M. Nikow, L. Letendre, and H. L. Dai J. Chem. Phys. 130, 044307 (2009). M. J. Wilhelm, M. Nikow, J. M. Smith, and H. L. Dai J. Phys. Chem. Lett. 4, 23 (2013).

  8. High sensitivity Cavity Ring Down Spectroscopy of N2O near 1.22 μm: (I) Rovibrational assignments and band-by-band analysis

    NASA Astrophysics Data System (ADS)

    Karlovets, E. V.; Campargue, A.; Kassi, S.; Perevalov, V. I.; Tashkun, S. A.

    2016-01-01

    The absorption spectrum of nitrous oxide (N2O) in natural isotopic abundance has been recorded near 1.22 μm by Cavity Ring Down Spectroscopy using an External Cavity Diode Laser (ECDL) as light source. The room temperature recordings were performed at a pressure of 10.0 Torr in the 7915-8334 cm-1 spectral range (1.26-1.19 μm). The typical noise equivalent absorption of the spectra, on the order of αmin~2×10-11 cm-1, allowed for the detection of lines with intensities on the order of 5×10-29 cm/molecule. More than 3300 transitions belonging to 64 bands of five nitrous oxide isotopologues (14N216O, 14N15N16O, 15N14N16O, 14N218O and 14N217O) have been rovibrationally assigned on the basis of the predictions of the effective Hamiltonian models developed for each isotopologue. For comparison, only 13 bands were previously measured by Fourier Transform spectroscopy in the studied region. All identified bands belong to the ΔP=13 and 14 series of transitions, where P=2V1+V2+4V3 is the polyad number (Vi are vibrational quantum numbers). The line positions and intensities are provided for all assigned lines. The maximum deviations between the measured position values and those predicted by the effective Hamiltonian models are about 0.2 cm-1 for the main isotopologue but reach values larger than 1 cm-1 for the less abundant minor isotopologues. The band-by-band analysis led to the determination of the rovibrational parameters of a total of 62 bands. The typical rms value of the (νobs-νfit) differences is 0.7×10-3 cm-1. Among the 62 bands, 49 are newly measured, for 13 others the rotational analysis is significantly improved and extended. A few resonance perturbations due to intra- and inter-polyad couplings are identified and discussed.

  9. The Excitation of HCN and HCO+ in the Galactic Center Circumnuclear Disk

    NASA Astrophysics Data System (ADS)

    Mills, E. A. C.; Güsten, R.; Requena-Torres, M. A.; Morris, M. R.

    2013-12-01

    We present new observations of HCN and HCO+ in the circumnuclear disk (CND) of the Galaxy, which we obtained with the Atacama Pathfinder Experiment telescope. We mapped emission in rotational lines of HCN J = 3-2, 4-3, and 8-7, as well as of HCO+ J = 3-2, 4-3, and 9-8. We also present spectra of H13CN J = 3-2 and 4-3 as well as H13CO+ J = 3-2 and 4-3 toward four positions in the CND. Using the intensities of all of these lines, we present an excitation analysis for each molecule using the non-LTE radiative transfer code RADEX. The HCN line intensities toward the northern emission peak of the CND yield log densities (cm-3) of 5.6^{+0.6}_{-0.6}, consistent with those measured with HCO+ as well as with densities recently reported for this region from an excitation analysis of highly excited lines of CO. These densities are too low for the gas to be tidally stable. The HCN line intensities toward the CND's southern emission peak yield log densities of 6.5^{+0.5}_{-0.7}, higher than densities determined for this part of the CND with CO (although the densities measured with HCO+, log [n] = 5.6^{+0.2}_{-0.2}, are more consistent with the CO-derived densities). We investigate whether the higher densities we infer from HCN are affected by midinfrared radiative excitation of this molecule through its 14 μm rovibrational transitions. We find that radiative excitation is important for at least one clump in the CND, where we additionally detect the J = 4-3, v 2 = 1 vibrationally excited transition of HCN, which is excited by dust temperatures of gsim125-150 K. If this hot dust is present elsewhere in the CND, it could lower our inferred densities, potentially bringing the HCN-derived densities for the southern part of the CND into agreement with those measured using HCO+ and CO. Additional sensitive, high-resolution submillimeter observations, as well as midinfrared observations, would be useful to assess the importance of the radiative excitation of HCN in this environment.

  10. The excitation of HCN and HCO{sup +} in the galactic center circumnuclear disk

    SciTech Connect

    Mills, E. A. C.; Güsten, R.; Requena-Torres, M. A.; Morris, M. R.

    2013-12-10

    We present new observations of HCN and HCO{sup +} in the circumnuclear disk (CND) of the Galaxy, which we obtained with the Atacama Pathfinder Experiment telescope. We mapped emission in rotational lines of HCN J = 3-2, 4-3, and 8-7, as well as of HCO{sup +} J = 3-2, 4-3, and 9-8. We also present spectra of H{sup 13}CN J = 3-2 and 4-3 as well as H{sup 13}CO{sup +} J = 3-2 and 4-3 toward four positions in the CND. Using the intensities of all of these lines, we present an excitation analysis for each molecule using the non-LTE radiative transfer code RADEX. The HCN line intensities toward the northern emission peak of the CND yield log densities (cm{sup –3}) of 5.6{sub −0.6}{sup +0.6}, consistent with those measured with HCO{sup +} as well as with densities recently reported for this region from an excitation analysis of highly excited lines of CO. These densities are too low for the gas to be tidally stable. The HCN line intensities toward the CND's southern emission peak yield log densities of 6.5{sub −0.7}{sup +0.5}, higher than densities determined for this part of the CND with CO (although the densities measured with HCO{sup +}, log [n] = 5.6{sub −0.2}{sup +0.2}, are more consistent with the CO-derived densities). We investigate whether the higher densities we infer from HCN are affected by midinfrared radiative excitation of this molecule through its 14 μm rovibrational transitions. We find that radiative excitation is important for at least one clump in the CND, where we additionally detect the J = 4-3, v {sub 2} = 1 vibrationally excited transition of HCN, which is excited by dust temperatures of ≳125-150 K. If this hot dust is present elsewhere in the CND, it could lower our inferred densities, potentially bringing the HCN-derived densities for the southern part of the CND into agreement with those measured using HCO{sup +} and CO. Additional sensitive, high-resolution submillimeter observations, as well as midinfrared observations, would be

  11. Experiments on excitation waves

    NASA Astrophysics Data System (ADS)

    Müller, S. C.

    Recent trends in the experimentation on chemical and biochemical excitation waves are presented. In the Belousov-Zhabotinsky reaction, which is the most suitable chemical laboratory system for the study of wave propagation in excitable medium, the efficient control of wave dynamics by electrical fields and by light illumination is illustrated. In particular, the effects of a feedback control are shown. Further new experiments in this system are concerned with three-dimensional topologies and boundary effects. Important biological applications are found in the aggregation of slime mould amoebae, in proton waves during oscillatory glycolysis, and in waves of spreading depression in neuronal tissue as studied by experiments in chicken retina. Numerical simulations with appropriate reaction-diffusion models complement a large number of these experimental findings.

  12. Magnetostrictive resonance excitation

    DOEpatents

    Schwarz, Ricardo B.; Kuokkala, Veli-Tapani

    1992-01-01

    The resonance frequency spectrum of a magnetostrictive sample is remotely determined by exciting the magnetostrictive property with an oscillating magnetic field. The permeability of a magnetostrictive material and concomitant coupling with a detection coil varies with the strain in the material whereby resonance responses of the sample can be readily detected. A suitable sample may be a magnetostrictive material or some other material having at least one side coated with a magnetostrictive material. When the sample is a suitable shape, i.e., a cube, rectangular parallelepiped, solid sphere or spherical shell, the elastic moduli or the material can be analytically determined from the measured resonance frequency spectrum. No mechanical transducers are required and the sample excitation is obtained without contact with the sample, leading to highly reproducible results and a measurement capability over a wide temperature range, e.g. from liquid nitrogen temperature to the Curie temperature of the magnetostrictive material.

  13. Excitable scale free networks

    NASA Astrophysics Data System (ADS)

    Copelli, M.; Campos, P. R. A.

    2007-04-01

    When a simple excitable system is continuously stimulated by a Poissonian external source, the response function (mean activity versus stimulus rate) generally shows a linear saturating shape. This is experimentally verified in some classes of sensory neurons, which accordingly present a small dynamic range (defined as the interval of stimulus intensity which can be appropriately coded by the mean activity of the excitable element), usually about one or two decades only. The brain, on the other hand, can handle a significantly broader range of stimulus intensity, and a collective phenomenon involving the interaction among excitable neurons has been suggested to account for the enhancement of the dynamic range. Since the role of the pattern of such interactions is still unclear, here we investigate the performance of a scale-free (SF) network topology in this dynamic range problem. Specifically, we study the transfer function of disordered SF networks of excitable Greenberg-Hastings cellular automata. We observe that the dynamic range is maximum when the coupling among the elements is critical, corroborating a general reasoning recently proposed. Although the maximum dynamic range yielded by general SF networks is slightly worse than that of random networks, for special SF networks which lack loops the enhancement of the dynamic range can be dramatic, reaching nearly five decades. In order to understand the role of loops on the transfer function we propose a simple model in which the density of loops in the network can be gradually increased, and show that this is accompanied by a gradual decrease of dynamic range.

  14. Harmonically excited orbital variations

    SciTech Connect

    Morgan, T.

    1985-08-06

    Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs.

  15. Fluorescence Excitation Models of Ammonia and Amidogen Radical (NH2) in Comets: Application to Comet C/2004 Q2 (Machholz)

    NASA Technical Reports Server (NTRS)

    Kawakita, Hideyo; Mumma, Michael J.

    2011-01-01

    Ammonia is a major reservoir of nitrogen atoms in cometary materials. However, detections of ammonia in comets are rare, with several achieved at radio wavelengths. A few more detections were obtained through near-infrared observations (around the 3 m wavelength region), but moderate relative velocity shifts are required to separate emission lines of cometary ammonia from telluric absorption lines in the 3 micron wavelength region. On the other hand, the amidogen radical (NH2 -- a photodissociation product of ammonia in the coma) also shows rovibrational emission lines in the 3 micron wavelength region. Thus, gas production rates for ammonia can be determined from the rovibrational emission lines of ammonia (directly) and amidogen radical (indirectly) simultaneously in the near-infrared. In this article, we present new fluorescence excitation models for cometary ammonia and amidogen radical in the near-infrared, and we apply these models to the near-infrared high-dispersion spectra of comet C/2004 Q2 (Machholz) to determine the mixing ratio of ammonia to water in the comet. Based on direct detection of NH3 lines, the mixing ratio of NH3/H2O is 0.46% +/- 0.03% in C/2004 Q2 (Machholz), in agreement with other results. The mixing ratio of ammonia determined from the NH2 observations (0.31% -- 0.79%) is consistent but has relatively larger error, owing to uncertainty in the photodissociation rates of ammonia. At the present level of accuracy, we confirm that NH3 could be the sole parent of NH2 in this comet.

  16. Fluorescence Excitation Models of Ammonia and Amidogen Radical (NH2) in Comets: Application to Comet C/2004 Q2 (Machholz)

    NASA Technical Reports Server (NTRS)

    Kawakita, Hideyo; Mumma, Michael J.

    2011-01-01

    Ammonia is a major reservoir of nitrogen atoms in cometary materials. However, detections of ammonia in comets are rare, with several achieved at radio wavelengths. A few more detections were obtained through near-infrared observations (around the 3 m wavelength region), but moderate relative velocity shifts are required to separate emission lines of cometary ammonia from telluric absorption lines in the 3 micron wavelength region. On the other hand, the amidogen radical (NH2 -- a photodissociation product of ammonia in the coma) also shows rovibrational emission lines in the 3 micron wavelength region. Thus, gas production rates for ammonia can be determined from the rovibrational emission lines of ammonia (directly) and amidogen radical (indirectly) simultaneously in the near-infrared. In this article, we present new fluorescence excitation models for cometary ammonia and amidogen radical in the near-infrared, and we apply these models to the near-infrared high-dispersion spectra of comet C/2004 Q2 (Machholz) to determine the mixing ratio of ammonia to water in the comet. Based on direct detection of NH3 lines, the mixing ratio of NH3/H2O is 0.46% +/- 0.03% in C/2004 Q2 (Machholz), in agreement with other results. The mixing ratio of ammonia determined from the NH2 observations (0.31% -- 0.79%) is consistent but has relatively larger error, owing to uncertainty in the photodissociation rates of ammonia. At the present level of accuracy, we confirm that NH3 could be the sole parent of NH2 in this comet.

  17. Pulse excitation of bolometer bridges

    NASA Technical Reports Server (NTRS)

    Rusk, S. J.

    1972-01-01

    Driving bolometer bridge by appropriately phased excitation pulses increases signal-to-noise ratio of bolometer sensor which operates on a chopped light beam. Method allows higher applied voltage than is possible by conventional ac or dc excitation.

  18. Apparatus for photon excited catalysis

    NASA Technical Reports Server (NTRS)

    Saffren, M. M. (Inventor)

    1977-01-01

    An apparatus is described for increasing the yield of photonically excited gas phase reactions by extracting excess energy from unstable, excited species by contacting the species with the surface of a finely divided solid.

  19. AKARI Near-infrared Spectroscopy of the Extended Green Object G318.05+0.09: Detection of CO Fundamental Ro-vibrational Emission

    NASA Astrophysics Data System (ADS)

    Onaka, Takashi; Mori, Tamami; Sakon, Itsuki; Ardaseva, Aleksandra

    2016-10-01

    We present the results of near-infrared (2.5-5.4 μm) long-slit spectroscopy of the extended green object (EGO) G318.05+0.09 with AKARI. Two distinct sources are found in the slit. The brighter source has strong red continuum emission with H2O ice, CO2 ice, and CO gas and ice absorption features at 3.0, 4.25 μm, 4.67 μm, respectively, while the other greenish object shows peculiar emission that has double peaks at around 4.5 and 4.7 μm. The former source is located close to the ultra compact H ii region IRAS 14498-5856 and is identified as an embedded massive young stellar object (YSO). The spectrum of the latter source can be interpreted by blueshifted (-3000 ˜ -6000 km s-1) optically thin emission of the fundamental ro-vibrational transitions (v=1{--}0) of CO molecules with temperatures of 12000-3700 K without noticeable H2 and H i emission. We discuss the nature of this source in terms of outflow associated with the young stellar object and supernova ejecta associated with a supernova remnant.

  20. Anharmonic rovibrational calculations of singlet cyclic C{sub 4} using a new ab initio potential and a quartic force field

    SciTech Connect

    Wang, Xiaohong; Bowman, Joel M.; Huang, Xinchuan; Lee, Timothy J.

    2013-12-14

    We report a CCSD(T)/cc-pCV5Z quartic force field (QFF) and a semi-global CCSD(T)-F12b/aug-cc-pVTZ potential energy surface (PES) for singlet, cyclic C{sub 4}. Vibrational fundamentals, combinations, and overtones are obtained using vibrational second-order perturbation theory (VPT2) and the vibrational configuration-interaction (VCI) approach. Agreement is within 10 cm{sup −1} between the VCI calculated fundamentals on the QFF and PES using the MULTIMODE (MM) program, and VPT2 and VCI results agree for the fundamentals. The agreement between VPT2-QFF and MM-QFF results is also good for the C{sub 4} combinations and overtones. The J = 1 and J = 2 rovibrational energies are reported from both VCI (MM) on the PES and VPT2 on the QFF calculations. The spectroscopic constants of {sup 12}C{sub 4} and two C{sub 2v}-symmetry, single {sup 13}C-substituted isotopologues are presented, which may help identification of cyclic C{sub 4} in future experimental analyses or astronomical observations.

  1. Highly Accurate Potential Energy Surface, Dipole Moment Surface, Rovibrational Energy Levels, and Infrared Line List for (32)S(16)O2 up to 8000 cm(exp -1)

    NASA Technical Reports Server (NTRS)

    Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.

    2014-01-01

    A purely ab initio potential energy surface (PES) was refined with selected (32)S(16)O2 HITRAN data. Compared to HITRAN, the root-mean-squares error (RMS) error for all J=0-80 rovibrational energy levels computed on the refined PES (denoted Ames-1) is 0.013 cm(exp -1). Combined with a CCSD(T)/aug-cc-pV(Q+d)Z dipole moment surface (DMS), an infrared (IR) line list (denoted Ames-296K) has been computed at 296K and covers up to 8,000 cm(exp -1). Compared to the HITRAN and CDMS databases, the intensity agreement for most vibrational bands is better than 85-90%. Our predictions for (34)S(16)O2 band origins, higher energy (32)S(16)O2 band origins and missing (32)S(16)O2 IR bands have been verified by most recent experiments and available HITRAN data. We conclude that the Ames-1 PES is able to predict (32/34)S(16)O2 band origins below 5500 cm(exp -1) with 0.01-0.03 cm(exp -1) uncertainties, and the Ames-296K line list provides continuous, reliable and accurate IR simulations. The Ka-dependence of both line position and line intensity errors is discussed. The line list will greatly facilitate SO2 IR spectral experimental analysis, as well as elimination of SO2 lines in high-resolution astronomical observations.

  2. Highly accurate potential energy surface, dipole moment surface, rovibrational energy levels, and infrared line list for 32S16O2 up to 8000 cm-1

    NASA Astrophysics Data System (ADS)

    Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.

    2014-03-01

    A purely ab initio potential energy surface (PES) was refined with selected 32S16O2 HITRAN data. Compared to HITRAN, the root-mean-squares error (σRMS) for all J = 0-80 rovibrational energy levels computed on the refined PES (denoted Ames-1) is 0.013 cm-1. Combined with a CCSD(T)/aug-cc-pV(Q+d)Z dipole moment surface (DMS), an infrared (IR) line list (denoted Ames-296K) has been computed at 296 K and covers up to 8000 cm-1. Compared to the HITRAN and CDMS databases, the intensity agreement for most vibrational bands is better than 85%-90%. Our predictions for 34S16O2 band origins, higher energy 32S16O2 band origins and missing 32S16O2 IR bands have been verified by most recent experiments and available HITRAN data. We conclude that the Ames-1 PES is able to predict 32/34S16O2 band origins below 5500 cm-1 with 0.01-0.03 cm-1 uncertainties, and the Ames-296K line list provides continuous, reliable and accurate IR simulations. The Ka-dependence of both line position and line intensity errors is discussed. The line list will greatly facilitate SO2 IR spectral experimental analysis, as well as elimination of SO2 lines in high-resolution astronomical observations.

  3. N2-, O2- and He-collision-induced broadening of sulfur dioxide ro-vibrational lines in the 9.2 μm atmospheric window

    NASA Astrophysics Data System (ADS)

    Tasinato, Nicola; Pietropolli Charmet, Andrea; Stoppa, Paolo; Giorgianni, Santi; Buffa, Giovanni

    2014-01-01

    Sulfur dioxide (SO2) is a molecule of considerable interest for both atmospheric chemistry and astrophysics. In the Earth's atmosphere, it enters in the sulfur cycle and it is ubiquitous present in polluted atmospheres, where it is responsible for acid rains. It is also of astrophysical and planetological importance, being present on Venus and in interstellar clouds. In this work the collisional broadening of a number of ν1 ro-vibrational lines of SO2 perturbed by N2, O2 and He are investigated at room temperature in the 9 μm atmospheric region by means of high resolution tunable diode laser (TDL) infrared spectroscopy. From N2- and O2-broadening coefficients, the broadening parameters of sulfur dioxide in air, useful for atmospheric applications, are derived as well. From the present measurements some conclusions on the quantum number dependence of the N2-, O2- and He-broadening coefficients are drawn. While the J dependence is weak for all the perturbers investigated, different trends with Ka are reported. N2-broadening coefficients show a slight decrease with increasing values of Ka, whereas O2 and He broadening cross sections first increase up to Ka″≈6 and then they keep a nearly constant value. A comparison and a brief discussion on the efficiency of self-, N2-, O2- and He-collisional dynamics are given. The data obtained represent a significant analysis on foreign broadening of SO2 useful for atmospheric remote sensing and astrophysical applications.

  4. Get excited: reappraising pre-performance anxiety as excitement.

    PubMed

    Brooks, Alison Wood

    2014-06-01

    Individuals often feel anxious in anticipation of tasks such as speaking in public or meeting with a boss. I find that an overwhelming majority of people believe trying to calm down is the best way to cope with pre-performance anxiety. However, across several studies involving karaoke singing, public speaking, and math performance, I investigate an alternative strategy: reappraising anxiety as excitement. Compared with those who attempt to calm down, individuals who reappraise their anxious arousal as excitement feel more excited and perform better. Individuals can reappraise anxiety as excitement using minimal strategies such as self-talk (e.g., saying "I am excited" out loud) or simple messages (e.g., "get excited"), which lead them to feel more excited, adopt an opportunity mind-set (as opposed to a threat mind-set), and improve their subsequent performance. These findings suggest the importance of arousal congruency during the emotional reappraisal process.

  5. Search for Gluonic Excitations

    SciTech Connect

    Eugenio, Paul

    2007-10-26

    Studies of meson spectra via strong decays provide insight regarding QCD at the confinement scale. These studies have led to phenomenological models for QCD such as the constituent quark model. However, QCD allows for a much richer spectrum of meson states which include extra states such as exotics, hybrids, multi-quarks, and glueballs. First discussion of the status of exotic meson searches is given followed by a discussion of plans at Jefferson Lab to double the energy of the machine to 12 GeV, which will allow us to access photoproduction of mesons in search for gluonic excited states.

  6. Search for Gluonic Excitations

    SciTech Connect

    Paul Eugenio

    2007-10-01

    Studies of meson spectra via strong decays provide insight regarding QCD at the confinement scale. These studies have led to phenomenological models for QCD such as the constituent quark model. However, QCD allows for a much richer spectrum of meson states which include extra states such as exotics, hybrids, multi-quarks, and glueballs. First discussion of the status of exotic meson searches is given followed by a discussion of plans at Jefferson Lab to double the energy of the machine to 12 GeV, which will allow us to access photoproduction of mesons in search for gluonic excited states.

  7. Metastable Interactions: Dissociative Excitation.

    DTIC Science & Technology

    1985-05-01

    participate. The mercuric halide compounds HgBr2 , HgCl 2 , and HgI2 are of recent interest because of laser output achieved on the B2 E - X2 E transition in...the * respective mercuric halide radicals in the range of 400-600 nm. Population inversion has been obtained by photodissociation and electron impact...excitation in mixtures o the mercuric - halide compounds and the rare gases. Chang and -* Burnham (3) have noted Improved laser efficiency and improved

  8. SHOCK-EXCITED OSCILLATOR

    DOEpatents

    Creveling, R.

    1957-12-17

    S> A shock-excited quartz crystal oscillator is described. The circuit was specifically designed for application in micro-time measuring work to provide an oscillator which immediately goes into oscillation upon receipt of a trigger pulse and abruptly ceases oscillation when a second pulse is received. To achieve the instant action, the crystal has a prestressing voltage applied across it. A monostable multivibrator receives the on and off trigger pulses and discharges a pulse through the crystal to initiate or terminate oscillation instantly.

  9. Using Diffusion Monte Carlo to Probe the Rotationally Excited States of H_3^+ and its Isotopologues

    NASA Astrophysics Data System (ADS)

    Wellen, Bethany A.; Petit, Andrew S.; McCoy, Anne B.

    2011-06-01

    H3-ND_n^+ are among the most abundant polyatomic ions in the universe. Moreover, the deuterated isotopologues are thought to play a key role in the astrochemical reactions governing the H/D fractionation of "metallic" species in the interstellar medium. An accurate quantum mechanical treatment of these species, as well as any reactions involving them, requires a methodology capable of capturing their large fluxionality as well as the constraints, due to particle exchange symmetries, on their physically allowed rovibrational states. Diffusion Monte Carlo (DMC) has been shown to be a highly successful technique for treating quantum zero-point effects of very floppy molecules and clusters and our group has recently developed a fixed-node DMC methodology capable of including the effects of rotational excitation. Here, we report the results of DMC calculations of the rotationally excited states of H_3^+ and its isotopologues. In particular, comparison with converged variational calculations involving states with J ≤ 20 provides the most thorough test yet of the range of quantum states over which the assumptions underlying our rotationally excited state DMC methodology can be reliably applied. Finally, the implications of this work on our overall goal of using DMC based methodologies to map out the energetics of the reaction of H3-ND_n^+ with HD will be discussed. T. R. Geballe and T. Oka, Science 312, 1610 (2006) E. Hugo, O. Asvany, and S. Schlemmer, J. Chem. Phys. 130, 164302 (2009) A. S. Petit and A. B. McCoy, J. Phys. Chem. A 113, 12706 (2009)

  10. Excitability in Dictyostelium development

    NASA Astrophysics Data System (ADS)

    Schwab, David

    2013-03-01

    Discovering how populations of cells reliably develop into complex multi-cellular structures is a key challenge in modern developmental biology. This requires an understanding of how networks at the single-cell level, when combined with intercellular signaling and environmental cues, give rise to the collective behaviors observed in cellular populations. I will present work in collaboration with the Gregor lab, showing that the signal-relay response of starved cells of the amoebae Dictyostelium discoideum can be well modeled as an excitable system. This is in contrast to existing models of the network that postulate a feed-forward cascade. I then extend the signal-relay model to describe how spatial gradient sensing may be achieved via excitability. One potential advantage of relying on feedback for gradient sensing is in preventing ``cheaters'' that do not produce signals from taking over the population. I then combine these models of single-cell signaling and chemotaxis to perform large-scale agent-based simulations of aggregating populations. This allows direct study of how variations in single-cell dynamics modify population behavior. In order to further test this model, I use the results of a screen for mutant cell lines that exhibit altered collective patterns. Finally, I use an existing FRET movie database of starved cell populations at varying cell densities and dilution rates to study heterogeneity in repeated spatio-temporal activity patterns.

  11. Length of excitable knots

    NASA Astrophysics Data System (ADS)

    Maucher, Fabian; Sutcliffe, Paul

    2017-07-01

    In this paper, we present extensive numerical simulations of an excitable medium to study the long-term dynamics of knotted vortex strings for all torus knots up to crossing number 11. We demonstrate that FitzHugh-Nagumo evolution preserves the knot topology for all the examples presented, thereby providing a field theory approach to the study of knots. Furthermore, the evolution yields a well-defined minimal length for each knot that is comparable to the ropelength of ideal knots. We highlight the role of the medium boundary in stabilizing the length of the knot and discuss the implications beyond torus knots. We also show that there is not a unique attractor within a given knot topology.

  12. CINE: Comet INfrared Excitation

    NASA Astrophysics Data System (ADS)

    de Val-Borro, Miguel; Cordiner, Martin A.; Milam, Stefanie N.; Charnley, Steven B.

    2017-08-01

    CINE calculates infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. One of the main mechanisms for molecular excitation in comets is the fluorescence by the solar radiation followed by radiative decay to the ground vibrational state. This command-line tool calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Fluorescence coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.

  13. VUV fluorescence following electron-impact dissociative excitation of CS{sub 2}

    SciTech Connect

    Brotton, S. J.; McConkey, J. W.

    2011-01-15

    Electron-impact dissociation of CS{sub 2} has been studied by observation of the atomic spectral emission features in the range 115-170 nm. Absolute photoemission cross sections are presented over the complete wavelength range for an incident electron energy of 100 eV. As an example, the measured cross section of the strong C i emission at 165.7 nm, which is a prominent feature in many solar and other extraterrestrial spectra, is (1.45{+-}0.19)x10{sup -18} cm{sup 2}. Comparison with earlier cross-sectional measurements suggest that these were too high by a factor of more than three. Excitation functions of the dominant C i (156.1 nm) and S i (147.4 nm) emission lines have been measured for electron-impact energies from threshold to 360 eV. From appearance energy measurements in the near-threshold region, likely fragmentation channels are identified which involve both two-fragment breakup and total fragmentation of the parent CS{sub 2}.

  14. High Resolution Rovibrational Spectroscopy of Jet-Cooled Phenyl Radical: the ν_{19} Out-Of Symmetric C-H Stretch

    NASA Astrophysics Data System (ADS)

    Buckingham, Grant T.; Chang, Chih-Hsuan; Nesbitt, David J.

    2013-06-01

    Phenyl radical has been studied via sub-Doppler infrared spectroscopy in a slit supersonic discharge expansion source, with assignments for the highest frequency b_{2} out-of-phase C-H symmetric stretch vibration (ν_{19}) unambiguously confirmed by ≤ 6 MHz (0.0002 cm^{-1}) agreement with microwave ground state combination differences of McMahon et al. [Astrophys. J. 590, L61-64 (2003)]. Least squares analysis of > 100 resolved rovibrational peaks in the sub-Doppler spectrum to a Watson Hamiltonian yields precision exited-state rotational constants and a vibrational band origin (ν_{0} = 3071.8915(4) cm^{-1}) consistent with a surprisingly small red-shift (0.9 cm^{-1}) with respect to Ar matrix isolation studies of Ellison and coworkers [J. Am. Chem. Soc. 123, 1977 (2001)]. Nuclear spin weights and inertial defects confirm the vibrationally averaged planarity and ^{2}A_{1} rovibronic symmetry of phenyl radical, with analysis of the rotational constants consistent with a modest C_{2v} distortion of the carbon backbone frame due to partial sp rehybridization of the σ C radical-center. Most importantly, despite the number of atoms (N = 11) and vibrational modes (3N-6 = 27), phenyl radical exhibits a remarkably clean jet cooled high resolution IR spectrum that shows no evidence of intramolecular vibrational relaxation (IVR) phenomena such as local or non-local perturbations due to strongly coupled nearby dark states. This provides strong support for the feasibility of high resolution infrared spectroscopy in other cyclic aromatic hydrocarbon radical systems.

  15. The CO2 absorption spectrum in the 2.3 μm transparency window by high sensitivity CRDS: (I) Rovibrational lines

    NASA Astrophysics Data System (ADS)

    Vasilchenko, S.; Konefal, M.; Mondelain, D.; Kassi, S.; Čermák, P.; Tashkun, S. A.; Perevalov, V. I.; Campargue, A.

    2016-11-01

    The absorption of carbon dioxide is very weak near 2.3 μm which makes this transparency window of particular interest for the study of Venus' lower atmosphere. As a consequence of the weakness of the transitions located in this region, previous experimental data are very scarce and spectroscopic databases provide calculated line lists which should be tested and validated by experiment. In this work, we use the Cavity Ring Down Spectroscopy (CRDS) technique for a high sensitivity characterization of the CO2 absorption spectrum in two spectral intervals of the 2.3 μm window: 4248-4257 and 4295-4380 cm-1 which were accessed using a Distributed Feed Back (DFB) diode laser and a Vertical External Cavity Surface Emitting Laser (VECSEL) as light sources, respectively. The achieved sensitivity (noise equivalent absorption, αmin, on the order of 5×10-10 cm-1) allowed detecting numerous new transitions with intensity values down to 5×10-30 cm/molecule. The rovibrational assignments were performed by comparison with available theoretical line lists in particular those obtained at IAO Tomsk using the global effective operator approach. Hot bands of the main isotopologue and 16O12C18O bands were found to be missing in the HITRAN database while they contribute importantly to the absorption in the region. Additional CRDS spectra of a CO2 sample highly enriched in 18O were recorded in order to improve the spectroscopy of this isotopologue. As a result about 700 lines of 16O12C18O, 16O12C17O, 17O12C18O, 12C18O2 and 13C18O2 were newly measured. The status of the different databases (HITRAN, CDSD, variational calculations) in the important 2.3 μm transparency window is discussed. Possible improvements to correct evidenced deficiencies are suggested.

  16. Infrared rovibrational spectroscopy of OH–C{sub 2}H{sub 2} in {sup 4}He nanodroplets: Parity splitting due to partially quenched electronic angular momentum

    SciTech Connect

    Douberly, Gary E. Liang, Tao; Raston, Paul L.; Marshall, Mark D.

    2015-04-07

    The T-shaped OH–C{sub 2}H{sub 2} complex is formed in helium droplets via the sequential pick-up and solvation of the monomer fragments. Rovibrational spectra of the a-type OH stretch and b-type antisymmetric CH stretch vibrations contain resolved parity splitting that reveals the extent to which electronic angular momentum of the OH moiety is quenched upon complex formation. The energy difference between the spin-orbit coupled {sup 2}B{sub 1} (A″) and {sup 2}B{sub 2} (A′) electronic states is determined spectroscopically to be 216 cm{sup −1} in helium droplets, which is 13 cm{sup −1} larger than in the gas phase [Marshall et al., J. Chem. Phys. 121, 5845 (2004)]. The effect of the helium is rationalized as a difference in the solvation free energies of the two electronic states. This interpretation is motivated by the separation between the Q(3/2) and R(3/2) transitions in the infrared spectrum of the helium-solvated {sup 2}Π{sub 3/2} OH radical. Despite the expectation of a reduced rotational constant, the observed Q(3/2) to R(3/2) splitting is larger than in the gas phase by ≈0.3 cm{sup −1}. This observation can be accounted for quantitatively by assuming the energetic separation between {sup 2}Π{sub 3/2} and {sup 2}Π{sub 1/2} manifolds is increased by ≈40 cm{sup −1} upon helium solvation.

  17. Front interaction induces excitable behavior

    NASA Astrophysics Data System (ADS)

    Parra-Rivas, P.; Matías, M. A.; Colet, P.; Gelens, L.; Walgraef, D.; Gomila, D.

    2017-02-01

    Spatially extended systems can support local transient excitations in which just a part of the system is excited. The mechanisms reported so far are local excitability and excitation of a localized structure. Here we introduce an alternative mechanism based on the coexistence of two homogeneous stable states and spatial coupling. We show the existence of a threshold for perturbations of the homogeneous state. Subthreshold perturbations decay exponentially. Superthreshold perturbations induce the emergence of a long-lived structure formed by two back to back fronts that join the two homogeneous states. While in typical excitability the trajectory follows the remnants of a limit cycle, here reinjection is provided by front interaction, such that fronts slowly approach each other until eventually annihilating. This front-mediated mechanism shows that extended systems with no oscillatory regimes can display excitability.

  18. Circular polarization of the Fe XXV x-ray lines following collisional excitation by longitudinally polarized electrons

    SciTech Connect

    Inal, M.K. ); Zhang, H.L.; Sampson, D.H. )

    1992-09-01

    The circular polarization of x-ray lines emitted by heliumlike iron collisionally excited by a longitudinally polarized electron beam has been investigated theoretically. The required collision strengths for excitation of the different {ital n}=2 and 3 magnetic sublevels from the 1{ital s}{sup 2} ground level have been calculated by two different distorted-wave methods and compared with each other. The agreement is generally good. One of these methods is semirelativistic, and the other is fully relativistic with QED effects included in the atomic structure part of the calculations. A high degree of circular polarization is obtained for the magnetic dipole 1 {sup 1}{ital S}{sub 0--}2 {sup 3}{ital S}{sub 1} and quadrupole 1 {sup 1}{ital S}{sub 0--}2 {sup 3}{ital P}{sub 2} lines, while the intercombination line 1 {sup 1}{ital S}{sub 0--}2 {sup 3}{ital P}{sub 1} is found to be almost completely circularly polarized in the near-threshold region. In addition to being of intrinsic interest for atomic collision physics, the reported results might have useful applications in future diagnostics of high-temperature plasmas with a view to providing information on the possible polarization of suprathermal electron beams.

  19. Optically excited states in positronium

    NASA Technical Reports Server (NTRS)

    Howell, R. H.; Ziock, Klaus P.; Magnotta, F.; Dermer, Charles D.; Failor, R. A.; Jones, K. M.

    1990-01-01

    Optical excitation are reported of the 1 3S-2 3P transition in positronium, and a second excitation from n=2 to higher n states. The experiment used light from two pulsed dye lasers. Changes in the positronium annihilation rate during and after the laser pulse were used to deduce the excited state populations. The n=2 level was found to be saturable and excitable to a substantial fraction of n=2 positronium to higher levels. Preliminary spectroscopic measurements were performed on n=14 and n=15 positronium.

  20. Fission fragment excited laser system

    DOEpatents

    McArthur, David A.; Tollefsrud, Philip B.

    1976-01-01

    A laser system and method for exciting lasing action in a molecular gas lasing medium which includes cooling the lasing medium to a temperature below about 150 K and injecting fission fragments through the lasing medium so as to preferentially excite low lying vibrational levels of the medium and to cause population inversions therein. The cooled gas lasing medium should have a mass areal density of about 5 .times. 10.sup.-.sup.3 grams/square centimeter, relaxation times of greater than 50 microseconds, and a broad range of excitable vibrational levels which are excitable by molecular collisions.

  1. a Semi-Classical Approach to the Calculation of Highly Excited Rotational Energies for Asymmetric-Top Molecules

    NASA Astrophysics Data System (ADS)

    Schmiedt, Hanno; Schlemmer, Stephan; Yurchenko, Sergei N.; Yachmenev, Andrey; Jensen, Per

    2017-06-01

    We report a new semi-classical method to compute highly excited rotational energy levels of an asymmetric-top molecule. The method forgoes the idea of a full quantum mechanical treatment of the ro-vibrational motion of the molecule. Instead, it employs a semi-classical Green's function approach to describe the rotational motion, while retaining a quantum mechanical description of the vibrations. Similar approaches have existed for some time, but the method proposed here has two novel features. First, inspired by the path integral method, periodic orbits in the phase space and tunneling paths are naturally obtained by means of molecular symmetry analysis. Second, the rigorous variational method is employed for the first time to describe the molecular vibrations. In addition, we present a new robust approach to generating rotational energy surfaces for vibrationally excited states; this is done in a fully quantum-mechanical, variational manner. The semi-classical approach of the present work is applied to calculating the energies of very highly excited rotational states and it reduces dramatically the computing time as well as the storage and memory requirements when compared to the fully quantum-mechanical variational approach. Test calculations for excited states of SO_2 yield semi-classical energies in very good agreement with the available experimental data and the results of fully quantum-mechanical calculations. We hope to be able to present at the meeting also semi-classical calculations of transition intensities. See also the open-access paper Phys. Chem. Chem. Phys. 19, 1847-1856 (2017). DOI: 10.1039/C6CP05589C

  2. The Excitable Membrane

    PubMed Central

    Offner, Franklin F.

    1972-01-01

    The model of the excitable membrane assumes common channels for Na+ and K+; the two ion species interact within the pores through their electrostatic forces. The electric field varies across the membrane and with time, as a result of ionic redistribution. Ionic flow is primarily controlled by energy barriers at the two interfaces and by Ca++ adsorption at the external interface. When the membrane is polarized, the high electric field at the external interface acting on the membrane fixed charge keeps the effective channel diameter small, so that only dihydrated ions can cross the interface. The higher energy required to partially dehydrate Na+ accounts for its lower permeability when polarized. Depolarized, the channel entrance can expand, permitting quadrihydrated ions to pass; the large initial Na+ flow is the result of the large concentration ratio across the interface. The effect at the internal interface is symmetric; Na+ crosses with greater difficulty when the membrane is depolarized. Na+ inactivation occurs when the ion distribution within the membrane has assumed its new steady-state value. Calculations based on parameters consistent with physicochemical data agree generally with a wide range of experiments. The model does not obey the two fundamental Hodgkin-Huxley (HH) postulates (independence principle, ion flow proportional to thermodynamic potential). In several instances the model predicts experimental results which are not predicted by the HH equations. ImagesFIGURE 12 PMID:4655662

  3. BDNF Depresses Excitability of Parvalbumin-Positive Interneurons through an M-Like Current in Rat Dentate Gyrus.

    PubMed

    Nieto-Gonzalez, Jose Luis; Jensen, Kimmo

    2013-01-01

    In addition to their classical roles in neuronal growth, survival and differentiation, neurotrophins are also rapid regulators of excitability, synaptic transmission and activity-dependent synaptic plasticity. We have recently shown that mature BDNF (Brain Derived Neurotrophic Factor), but not proBDNF, modulates the excitability of interneurons in dentate gyrus within minutes. Here, we used brain slice patch-clamp recordings to study the mechanisms through which BDNF modulates the firing of interneurons in rat dentate gyrus by binding to TrkB receptors. Bath application of BDNF (15 ng/ml) under current-clamp decreased the firing frequency (by 80%) and input resistance, blocking the delayed firing observed at near-threshold voltage ranges, with no changes in resting membrane potential or action potential waveform. Using TEA (tetraethylammonium), or XE991(a Kv7/KCNQ channel antagonist), the effect of BDNF was abolished, whereas application of retigabine (a Kv7/KCNQ channel opener) mimicked the effect of BDNF, suggesting that the M-current could be implicated in the modulation of the firing. In voltage-clamp experiments, BDNF increased the M-like current amplitude with no change in holding current. This effect was again blocked by XE991 and mimicked by retigabine, the latter accompanied with a change in holding current. In agreement with the electrophysiology, parvalbumin-positive interneurons co-expressed TrkB receptors and Kv7.2/KCNQ2 channels. In conclusion, BDNF depresses the excitability of interneurons by activating an M-like current and possibly blocking Kv1 channels, thereby controlling interneuron resting membrane potential and excitability.

  4. Double excitations in finite systems.

    PubMed

    Romaniello, P; Sangalli, D; Berger, J A; Sottile, F; Molinari, L G; Reining, L; Onida, G

    2009-01-28

    Time-dependent density-functional theory (TDDFT) is widely used in the study of linear response properties of finite systems. However, there are difficulties in properly describing excited states, which have double- and higher-excitation characters, which are particularly important in molecules with an open-shell ground state. These states would be described if the exact TDDFT kernel were used; however, within the adiabatic approximation to the exchange-correlation (xc) kernel, the calculated excitation energies have a strict single-excitation character and are fewer than the real ones. A frequency-dependent xc kernel could create extra poles in the response function, which would describe states with a multiple-excitation character. We introduce a frequency-dependent xc kernel, which can reproduce, within TDDFT, double excitations in finite systems. In order to achieve this, we use the Bethe-Salpeter equation with a dynamically screened Coulomb interaction W(omega), which can describe these excitations, and from this we obtain the xc kernel. Using a two-electron model system, we show that the frequency dependence of W does indeed introduce the double excitations that are instead absent in any static approximation of the electron-hole screening.

  5. Excited waves in shear layers

    NASA Technical Reports Server (NTRS)

    Bechert, D. W.

    1982-01-01

    The generation of instability waves in free shear layers is investigated. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. The acoustical shear layer excitation by a source further away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. The theory is then extended to two streams on both sides of the shear layer having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. A reference quantity is found for the magnitude of the excited instability waves. For a comparison with measurements, numerical computations of the velocity field outside the shear layer were carried out.

  6. Vibrational excitation induces double reaction.

    PubMed

    Huang, Kai; Leung, Lydie; Lim, Tingbin; Ning, Zhanyu; Polanyi, John C

    2014-12-23

    Electron-induced reaction at metal surfaces is currently the subject of extensive study. Here, we broaden the range of experimentation to a comparison of vibrational excitation with electronic excitation, for reaction of the same molecule at the same clean metal surface. In a previous study of electron-induced reaction by scanning tunneling microscopy (STM), we examined the dynamics of the concurrent breaking of the two C-I bonds of ortho-diiodobenzene physisorbed on Cu(110). The energy of the incident electron was near the electronic excitation threshold of E0=1.0 eV required to induce this single-electron process. STM has been employed in the present work to study the reaction dynamics at the substantially lower incident electron energies of 0.3 eV, well below the electronic excitation threshold. The observed increase in reaction rate with current was found to be fourth-order, indicative of multistep reagent vibrational excitation, in contrast to the first-order rate dependence found earlier for electronic excitation. The change in mode of excitation was accompanied by altered reaction dynamics, evidenced by a different pattern of binding of the chemisorbed products to the copper surface. We have modeled these altered reaction dynamics by exciting normal modes of vibration that distort the C-I bonds of the physisorbed reagent. Using the same ab initio ground potential-energy surface as in the prior work on electronic excitation, but with only vibrational excitation of the physisorbed reagent in the asymmetric stretch mode of C-I bonds, we obtained the observed alteration in reaction dynamics.

  7. Free electrons and ionic liquids: study of excited states by means of electron-energy loss spectroscopy and the density functional theory multireference configuration interaction method.

    PubMed

    Regeta, Khrystyna; Bannwarth, Christoph; Grimme, Stefan; Allan, Michael

    2015-06-28

    The technique of low energy (0-30 eV) electron impact spectroscopy, originally developed for gas phase molecules, is applied to room temperature ionic liquids (IL). Electron energy loss (EEL) spectra recorded near threshold, by collecting 0-2 eV electrons, are largely continuous, assigned to excitation of a quasi-continuum of high overtones and combination vibrations of low-frequency modes. EEL spectra recorded by collecting 10 eV electrons show predominantly discrete vibrational and electronic bands. The vibrational energy-loss spectra correspond well to IR spectra except for a broadening (∼0.04 eV) caused by the liquid surroundings, and enhanced overtone activity indicating a contribution from resonant excitation mechanism. The spectra of four representative ILs were recorded in the energy range of electronic excitations and compared to density functional theory multireference configuration interaction (DFT/MRCI) calculations, with good agreement. The spectra up to about 8 eV are dominated by π-π* transitions of the aromatic cations. The lowest bands were identified as triplet states. The spectral region 2-8 eV was empty in the case of a cation without π orbitals. The EEL spectrum of a saturated solution of methylene green in an IL band showed the methylene green EEL band at 2 eV, indicating that ILs may be used as a host to study nonvolatile compounds by this technique in the future.

  8. Systematic comparison of positron- and electron-impact excitation of the {nu}{sub 3} vibrational mode of CF{sub 4}

    SciTech Connect

    Marler, J. P.; Surko, C. M.

    2005-12-15

    Absolute measurements are presented for the excitation of the {nu}{sub 3} vibrational mode in CF{sub 4} by positron and electron impact from 0.1 to 2 eV. To minimize systematic differences, these measurements were made using the same trap-based electron or positron beam, associated experimental apparatus, and procedures. Unlike other vibrational excitation cross sections studied to date, the near-threshold cross section for the {nu}{sub 3} vibrational mode in CF{sub 4} is similar, both in magnitude and shape, for positrons and electrons. Comparison of the cross sections with an analytic Born dipole model yields good agreement, while comparison of this model with other measured positron-impact vibrational cross sections indicates that the contribution of this long-range dipole coupling varies widely. The maximum value of the cross section in CF{sub 4} is the largest of any positron-impact vibrational excitation cross section measured to date. This provides a likely explanation of the observation that CF{sub 4} is very effective when used as a buffer gas to cool positron gases and plasmas.

  9. FLUORESCENCE EXCITATION MODELS OF AMMONIA AND AMIDOGEN RADICAL (NH{sub 2}) IN COMETS: APPLICATION TO COMET C/2004 Q2 (MACHHOLZ)

    SciTech Connect

    Kawakita, Hideyo; Mumma, Michael J.

    2011-02-01

    Ammonia is a major reservoir of nitrogen atoms in cometary materials. However, detections of ammonia in comets are rare, with several achieved at radio wavelengths. A few more detections were obtained through near-infrared observations (around the 3 {mu}m wavelength region), but moderate relative velocity shifts are required to separate emission lines of cometary ammonia from telluric absorption lines in the 3 {mu}m wavelength region. On the other hand, the amidogen radical (NH{sub 2}-a photodissociation product of ammonia in the coma) also shows rovibrational emission lines in the 3 {mu}m wavelength region. Thus, gas production rates for ammonia can be determined from the rovibrational emission lines of ammonia (directly) and amidogen radical (indirectly) simultaneously in the near-infrared. In this article, we present new fluorescence excitation models for cometary ammonia and amidogen radical in the near-infrared, and we apply these models to the near-infrared high-dispersion spectra of comet C/2004 Q2 (Machholz) to determine the mixing ratio of ammonia to water in the comet. Based on direct detection of NH{sub 3} lines, the mixing ratio of NH{sub 3}/H{sub 2}O is 0.46% {+-} 0.03% in C/2004 Q2 (Machholz), in agreement with other results. The mixing ratio of ammonia determined from the NH{sub 2} observations (0.31%-0.79%) is consistent but has relatively larger error, owing to uncertainty in the photodissociation rates of ammonia. At the present level of accuracy, we confirm that NH{sub 3} could be the sole parent of NH{sub 2} in this comet.

  10. Coulomb excitations of monolayer germanene

    NASA Astrophysics Data System (ADS)

    Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa

    2017-01-01

    The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes.

  11. Coulomb excitations of monolayer germanene

    PubMed Central

    Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa

    2017-01-01

    The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes. PMID:28091555

  12. Excitations of strange bottom baryons

    NASA Astrophysics Data System (ADS)

    Woloshyn, R. M.

    2016-09-01

    The ground-state and first-excited-state masses of Ωb and Ω_{bb} baryons are calculated in lattice QCD using dynamical 2 + 1 flavour gauge fields. A set of baryon operators employing different combinations of smeared quark fields was used in the framework of the variational method. Results for radial excitation energies were confirmed by carrying out a supplementary multiexponential fitting analysis. Comparison is made with quark model calculations.

  13. Collisional excitation of interstellar formaldehyde

    NASA Technical Reports Server (NTRS)

    Green, S.; Garrison, B. J.; Lester, W. A., Jr.; Miller, W. H.

    1978-01-01

    Previous calculations for rates of excitation of ortho-H2CO by collisions with He have been extended to higher rotational levels and kinetic temperatures to 80 K. Rates for para-H2CO have also been computed. Pressure-broadening widths for several spectral lines have been obtained from these calculations and are found to agree with recent data within the experimental uncertainty of 10%. Excitation of formaldehyde by collisions with H2 molecules is also discussed.

  14. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  15. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  16. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  17. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  18. 46 CFR 111.12-3 - Excitation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...

  19. Redox Control of Cardiac Excitability

    PubMed Central

    Aggarwal, Nitin T.

    2013-01-01

    Abstract Reactive oxygen species (ROS) have been associated with various human diseases, and considerable attention has been paid to investigate their physiological effects. Various ROS are synthesized in the mitochondria and accumulate in the cytoplasm if the cellular antioxidant defense mechanism fails. The critical balance of this ROS synthesis and antioxidant defense systems is termed the redox system of the cell. Various cardiovascular diseases have also been affected by redox to different degrees. ROS have been indicated as both detrimental and protective, via different cellular pathways, for cardiac myocyte functions, electrophysiology, and pharmacology. Mostly, the ROS functions depend on the type and amount of ROS synthesized. While the literature clearly indicates ROS effects on cardiac contractility, their effects on cardiac excitability are relatively under appreciated. Cardiac excitability depends on the functions of various cardiac sarcolemal or mitochondrial ion channels carrying various depolarizing or repolarizing currents that also maintain cellular ionic homeostasis. ROS alter the functions of these ion channels to various degrees to determine excitability by affecting the cellular resting potential and the morphology of the cardiac action potential. Thus, redox balance regulates cardiac excitability, and under pathological regulation, may alter action potential propagation to cause arrhythmia. Understanding how redox affects cellular excitability may lead to potential prophylaxis or treatment for various arrhythmias. This review will focus on the studies of redox and cardiac excitation. Antioxid. Redox Signal. 18, 432–468. PMID:22897788

  20. Electron-excited molecule interactions

    SciTech Connect

    Christophorou, L.G. Tennessee Univ., Knoxville, TN . Dept. of Physics)

    1991-01-01

    In this paper the limited but significant knowledge to date on electron scattering from vibrationally/rotationally excited molecules and electron scattering from and electron impact ionization of electronically excited molecules is briefly summarized and discussed. The profound effects of the internal energy content of a molecule on its electron attachment properties are highlighted focusing in particular on electron attachment to vibrationally/rotationally and to electronically excited molecules. The limited knowledge to date on electron-excited molecule interactions clearly shows that the cross sections for certain electron-molecule collision processes can be very different from those involving ground state molecules. For example, optically enhanced electron attachment studies have shown that electron attachment to electronically excited molecules can occur with cross sections 10{sup 6} to 10{sup 7} times larger compared to ground state molecules. The study of electron-excited molecule interactions offers many experimental and theoretical challenges and opportunities and is both of fundamental and technological significance. 54 refs., 15 figs.

  1. Electrostatic Tuning of Cellular Excitability

    PubMed Central

    Börjesson, Sara I.; Parkkari, Teija; Hammarström, Sven; Elinder, Fredrik

    2010-01-01

    Abstract Voltage-gated ion channels regulate the electric activity of excitable tissues, such as the heart and brain. Therefore, treatment for conditions of disturbed excitability is often based on drugs that target ion channels. In this study of a voltage-gated K channel, we propose what we believe to be a novel pharmacological mechanism for how to regulate channel activity. Charged lipophilic substances can tune channel opening, and consequently excitability, by an electrostatic interaction with the channel's voltage sensors. The direction of the effect depends on the charge of the substance. This was shown by three compounds sharing an arachidonyl backbone but bearing different charge: arachidonic acid, methyl arachidonate, and arachidonyl amine. Computer simulations of membrane excitability showed that small changes in the voltage dependence of Na and K channels have prominent impact on excitability and the tendency for repetitive firing. For instance, a shift in the voltage dependence of a K channel with −5 or +5 mV corresponds to a threefold increase or decrease in K channel density, respectively. We suggest that electrostatic tuning of ion channel activity constitutes a novel and powerful pharmacological approach with which to affect cellular excitability. PMID:20141752

  2. Atomic, Molecular, and Optical Physics: Optical Excitation Function of H(1s-2p) Produced by electron Impact from Threshold to 1.8 keV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Slevin, J. A.; Shemansky, D. E.; McConkey, J. W.; Bray, I.; Dziczek, D.; Kanik, I.; Ajello, J. M.

    1997-01-01

    The optical excitation function of prompt Lyman-Alpha radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet mono- chromator system was used to measure the emitted Lyman-Alpha radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Statistical and known systematic uncertainties in our data range from +/- 4% near threshold to +/- 2% at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close- coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10% level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7% of the CCC calculations over the 14 eV-1.8 keV range. The present CCC calculations converge on the Bethe- Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3% is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV - 1.8 keV energy range.

  3. Performance seeking control excitation mode

    NASA Technical Reports Server (NTRS)

    Schkolnik, Gerard

    1995-01-01

    Flight testing of the performance seeking control (PSC) excitation mode was successfully completed at NASA Dryden on the F-15 highly integrated digital electronic control (HIDEC) aircraft. Although the excitation mode was not one of the original objectives of the PSC program, it was rapidly prototyped and implemented into the architecture of the PSC algorithm, allowing valuable and timely research data to be gathered. The primary flight test objective was to investigate the feasibility of a future measurement-based performance optimization algorithm. This future algorithm, called AdAPT, which stands for adaptive aircraft performance technology, generates and applies excitation inputs to selected control effectors. Fourier transformations are used to convert measured response and control effector data into frequency domain models which are mapped into state space models using multiterm frequency matching. Formal optimization principles are applied to produce an integrated, performance optimal effector suite. The key technical challenge of the measurement-based approach is the identification of the gradient of the performance index to the selected control effector. This concern was addressed by the excitation mode flight test. The AdAPT feasibility study utilized the PSC excitation mode to apply separate sinusoidal excitation trims to the controls - one aircraft, inlet first ramp (cowl), and one engine, throat area. Aircraft control and response data were recorded using on-board instrumentation and analyzed post-flight. Sensor noise characteristics, axial acceleration performance gradients, and repeatability were determined. Results were compared to pilot comments to assess the ride quality. Flight test results indicate that performance gradients were identified at all flight conditions, sensor noise levels were acceptable at the frequencies of interest, and excitations were generally not sensed by the pilot.

  4. A quantum-rovibrational-state-selected study of the proton-transfer reaction H2(+)(X(2)Σ: v(+) = 1-3; N(+) = 0-3) + Ne → NeH(+) + H using the pulsed field ionization-photoion method: observation of the rotational effect near the reaction threshold.

    PubMed

    Xiong, Bo; Chang, Yih-Chung; Ng, Cheuk-Yiu

    2017-07-19

    Using the sequential electric field pulsing scheme for vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection, we have successfully prepared H2(+)(X(2)Σ: v(+) = 1-3; N(+) = 0-5) ions in the form of an ion beam in single quantum-rovibrational-states with high purity, high intensity, and narrow laboratory kinetic energy spread (ΔElab ≈ 0.05 eV). This VUV-PFI-PI ion source, when coupled with the double-quadrupole double-octupole ion-molecule reaction apparatus, has made possible a systematic examination of the vibrational- as well as rotational-state effects on the proton transfer reaction of H2(+)(X(2)Σ: v(+); N(+)) + Ne. Here, we present the integral cross sections [σ(v(+); N(+))'s] for the H2(+)(v(+) = 1-3; N(+) = 0-3) + Ne → NeH(+) + H reaction observed in the center-of-mass kinetic energy (Ecm) range of 0.05-2.00 eV. The σ(v(+) = 1, N(+) = 1) exhibits a distinct Ecm onset, which is found to agree with the endothermicity of 0.27 eV for the proton transfer process after taking into account of experimental uncertainties. Strong v(+)-vibrational enhancements are observed for σ(v(+) = 1-3, N(+)) in the Ecm range of 0.05-2.00 eV. While rotational excitations appear to have little effect on σ(v(+) = 3, N(+)), a careful search leads to the observation of moderate N(+)-rotational enhancements at v(+) = 2: σ(v(+) = 2; N(+) = 0) < σ(v(+) = 2; N(+) = 1) < σ(v(+) = 2; N(+) = 2) < σ(v(+) = 2; N(+) = 3), where the formation of NeH(+) is near thermal-neutral. The σ(v(+) = 1-3, N(+) = 0-3) values obtained here are compared with previous experimental results and the most recent state-of-the-art quantum dynamics predictions. We hope that these new experimental results would further motivate more rigorous theoretical calculations on the dynamics of this prototypical ion-molecule reaction.

  5. Excitation with quantum light. I. Exciting a harmonic oscillator

    NASA Astrophysics Data System (ADS)

    Carreño, J. C. López; Laussy, F. P.

    2016-12-01

    We present a two-part study of the excitation of an optical target by quantum light. In this first part, we introduce the problematic and address the first case of interest, that of exciting the quantum harmonic oscillator, corresponding to, e.g., a single-mode passive cavity or a noninteracting bosonic field. We introduce a mapping of the Hilbert space that allows to chart usefully the accessible regions. We then consider the quantum excitation from single-photon sources in the form of a two-level system under various regimes of (classical) pumping: incoherent, coherent, and in the Mollow triplet regime. We close this first part with an overview of the material to be covered in the subsequent work.

  6. Sadomasochism, sexual excitement, and perversion.

    PubMed

    Kernberg, O F

    1991-01-01

    Sadomasochism, an ingredient of infantile sexuality, is an essential part of normal sexual functioning and love relations, and of the very nature of sexual excitement. Sadomasochistic elements are also present in all sexual perversions. Sadomasochism starts out as the potential for erotic masochism in both sexes, and represents a very early capacity to link aggression with the libidinal elements of sexual excitement. Sexual excitement may be considered a basic affect that overcomes primitive splitting of love and hatred. Erotic desire is a more mature form of sexual excitement. Psychoanalytic exploration makes it possible to uncover the unconscious components of sexual excitement: wishes for symbiotic fusion and for aggressive penetration and intermingling; bisexual identifications; the desire to transgress oedipal prohibitions and the secretiveness of the primal scene, and to violate the boundaries of a teasing and withholding object. The relation between these wishes and the development of erotic idealization processes in both sexes is explored in the context of a critical review of the pertinent psychoanalytic literature.

  7. Vibrationally Excited c-C_3H_2 Re-Visited New Laboratory Measurements and Theoretical Calculations

    NASA Astrophysics Data System (ADS)

    Gupta, Harshal; Westerfield, J. H.; Baraban, Joshua H.; Changala, Bryan; Thorwirth, Sven; Stanton, John F.; Martin-Drumel, Marie-Aline; Pirali, Olivier; Gottlieb, Carl A.; McCarthy, Michael C.

    2017-06-01

    Cyclopropenylidene, c-C_3H_2, is one of the more abundant organic molecules in the interstellar medium, as evidenced from astronomical detection of its single ^{13}C and both its singly- and doubly-deuterated isotopic species. For this reason, vibrational satellites are of considerable astronomical interest, and were the primary motivation for the earlier laboratory work by Mollaaghababa and co-workers [1]. The recent detection of intense unidentified lines near 18 GHz in a hydrocarbon discharge by FT microwave spectroscopy has spurred a renewed search for the vibrational satellite transitions of c-C_3H_2. Several strong lines have been definitively assigned to the v_6 progression on the basis of follow-up measurements at 3 mm, double resonance and millimeter-wave absorption spectroscopy, and new theoretical calculations using a rovibrational VMP2 method [2] and a high-quality ab initio potential energy surface. The treatment was applied to several excited states as well as the ground state, and included deperturbation of Coriolis interactions. [1] R. Mollaaghababa, C.A. Gottlieb, J. M. Vrtilek, and P. Thaddeus, J. Chem. Phys., 99, 890-896 (1992). [2] P. B. Changala and J. H. Baraban. J. Chem. Phys., 145, 174106 (2016).

  8. Modeling excitable systems: Reentrant tachycardia

    NASA Astrophysics Data System (ADS)

    Lancaster, Jarrett L.; Hellen, Edward H.; Leise, Esther M.

    2010-01-01

    Excitable membranes are an important type of nonlinear dynamical system, and their study can be used to provide a connection between physical and biological circuits. We discuss two models of excitable membranes important in cardiac and neural tissues. One model is based on the Fitzhugh-Nagumo equations, and the other is based on a three-transistor excitable circuit. We construct a circuit that simulates reentrant tachycardia and its treatment by surgical ablation. This project is appropriate for advanced undergraduates as a laboratory capstone project or as a senior thesis or honors project and can also be a collaborative project, with one student responsible for the computational predictions and another for the circuit construction and measurements.

  9. Recurrent Excitation in Neocortical Circuits

    NASA Astrophysics Data System (ADS)

    Douglas, Rodney J.; Koch, Christof; Mahowald, Misha; Martin, Kevan A. C.; Suarez, Humbert H.

    1995-08-01

    The majority of synapses in the mammalian cortex originate from cortical neurons. Indeed, the largest input to cortical cells comes from neighboring excitatory cells. However, most models of cortical development and processing do not reflect the anatomy and physiology of feedback excitation and are restricted to serial feedforward excitation. This report describes how populations of neurons in cat visual cortex can use excitatory feedback, characterized as an effective "network conductance," to amplify their feedforward input signals and demonstrates how neuronal discharge can be kept proportional to stimulus strength despite strong, recurrent connections that threaten to cause runaway excitation. These principles are incorporated into models of cortical direction and orientation selectivity that emphasize the basic design principles of cortical architectures.

  10. Indirect excitation of ultrafast demagnetization

    DOE PAGES

    Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; ...

    2016-01-06

    Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset andmore » at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. As a result, our data thus confirm recent theoretical predictions.« less

  11. Indirect excitation of ultrafast demagnetization

    PubMed Central

    Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; Delaunay, Renaud; Müller, Leonard; Berntsen, Magnus H.; Grübel, Gerhard; Malinowski, Grégory; Weier, Christian; Gautier, Julien; Lambert, Guillaume; Zeitoun, Philippe; Gutt, Christian; Jal, Emmanuelle; Reid, Alexander H.; Granitzka, Patrick W.; Jaouen, Nicolas; Dakovski, Georgi L.; Moeller, Stefan; Minitti, Michael P.; Mitra, Ankush; Carron, Sebastian; Pfau, Bastian; von Korff Schmising, Clemens; Schneider, Michael; Eisebitt, Stefan; Lüning, Jan

    2016-01-01

    Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset and at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. Our data thus confirm recent theoretical predictions. PMID:26733106

  12. Indirect excitation of ultrafast demagnetization

    SciTech Connect

    Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; Delaunay, Renaud; Müller, Leonard; Berntsen, Magnus H.; Grübel, Gerhard; Malinowski, Grégory; Weier, Christian; Gautier, Julien; Lambert, Guillaume; Zeitoun, Philippe; Gutt, Christian; Jal, Emmanuelle; Reid, Alexander H.; Granitzka, Patrick W.; Jaouen, Nicolas; Dakovski, Georgi L.; Moeller, Stefan; Minitti, Michael P.; Mitra, Ankush; Carron, Sebastian; Pfau, Bastian; von Korff Schmising, Clemens; Schneider, Michael; Eisebitt, Stefan; Lüning, Jan

    2016-01-06

    Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset and at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. As a result, our data thus confirm recent theoretical predictions.

  13. Stochastic excitation of stellar oscillations

    NASA Astrophysics Data System (ADS)

    Samadi, Reza

    2001-05-01

    Since more than about thirty years, solar oscillations are thought to be excited stochastically by the turbulent motions in the solar convective zone. It is currently believed that oscillations of stars lower than 2 solar masses - which possess an upper convective zone - are excited stochastically by turbulent convection in their outer layers. Providing that accurate measurements of the oscillation amplitudes and damping rates are available it is possible to evaluate the power injected into the modes and thus - by comparison with the observations - to constrain current theories. A recent theoretical work (Samadi & Goupil, 2001; Samadi et al., 2001) supplements and reinforces the theory of stochastic excitation of star vibrations. This process was generalized to a global description of the turbulent state of their convective zone. The comparison between observation and theory, thus generalized, will allow to better know the turbulent spectrum of stars, and this in particular thanks to the COROT mission.

  14. Excitation optimization for damage detection

    SciTech Connect

    Bement, Matthew T; Bewley, Thomas R

    2009-01-01

    A technique is developed to answer the important question: 'Given limited system response measurements and ever-present physical limits on the level of excitation, what excitation should be provided to a system to make damage most detectable?' Specifically, a method is presented for optimizing excitations that maximize the sensitivity of output measurements to perturbations in damage-related parameters estimated with an extended Kalman filter. This optimization is carried out in a computationally efficient manner using adjoint-based optimization and causes the innovations term in the extended Kalman filter to be larger in the presence of estimation errors, which leads to a better estimate of the damage-related parameters in question. The technique is demonstrated numerically on a nonlinear 2 DOF system, where a significant improvement in the damage-related parameter estimation is observed.

  15. Excited Negative Ions and Molecules and Negative Ion Production

    DTIC Science & Technology

    1992-01-01

    the Journal of Chemical Physics . 2 4. ELECTRON AFFINITY OF TUNGSTEN TRIOXIDE Molecules of high electron affinity have been of interest...energy (electronic plus rovibrational). The results have been submitted for publication in the Journal of Chemical Physics . A preprint is included as...have made a reasonable analysis of the NH data, which will be prepared for publication in the Journal of Chemical Physics . 9.

  16. Calculation of molecular excitation rates

    NASA Technical Reports Server (NTRS)

    Flynn, George

    1993-01-01

    State-to-state collisional excitation rates for interstellar molecules observed by radio astronomers continue to be required to interpret observed line intensities in terms of local temperatures and densities. A problem of particular interest is collisional excitation of water which is important for modeling the observed interstellar masers. In earlier work supported by a different NASA Grant, excitation of water in collisions with He atoms was studied; after many years of successively more refined calculations that problem now seems to be well understood, and discrepancies with earlier experimental data for related (pressure broadening) phenomena are believed to reflect experimental errors. Because of interstellar abundances, excitation by H2, the dominant interstellar species, is much more important than excitation by He, although it has been argued that rates for excitation by these are similar. Under the current grant theoretical study of this problem has begun which is greatly complicated by the additional degrees of freedom which must be included both in determining the interaction potential and also in the molecular scattering calculation. We have now computed the interaction forces for nearly a thousand molecular geometries and are close to having an acceptable global fit to these points which is necessary for the molecular dynamics calculations. Also, extensive modifications have been made to the molecular scattering code, MOLSCAT. These included coding the rotational basis sets and coupling matrix elements required for collisions of an asymmetric top with a linear rotor. A new method for numerical solution of the coupled equations has been incorporated. Because of the long-ranged nature of the water-hydrogen interaction it is necessary to integrate the equations to rather large intermolecular separations, and the integration methods previously available in MOLSCAT are not ideal for such cases. However, the method used by Alexander in his HIBRIDON code is

  17. Excited-to-excited-state scattering using weak measurements

    NASA Astrophysics Data System (ADS)

    U, Satya Sainadh; Narayanan, Andal

    2015-11-01

    Weak measurements are a subset of measurement processes in quantum mechanics wherein the system, which is being measured, interacts very weakly with the measuring apparatus. Measurement values of observables undergoing a weak interaction and their amplification are concepts that have sharpened our understanding of interaction processes in quantum mechanics. Recent experiments show that naturally occurring processes such as resonance fluorescence from excited states of an atom can exhibit weak value amplification effect. In this paper we theoretically analyze the process of elastic resonance fluorescence from a V -type three-level atomic system, using the well-known Weiskopff-Wigner (WW) theory of spontaneous emission. Within this theory we show that a weak interaction regime can be identified and for suitable choices of initial and final excited states the mean scattering time between these states show an amplification effect during interaction with the vacuum bath modes of the electromagnetic field. We thus show that a system-bath interaction can show weak value amplification. Using our theory we reproduce the published experimental results carried out in such a system. More importantly, our theory can calculate scattering time scales in elastic resonance scattering between multiple excited states of a single atom or between common excited state configurations of interacting multiatom systems.

  18. Autoresonant Excitation of Antiproton Plasmas

    NASA Astrophysics Data System (ADS)

    Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Butler, E.; Carpenter, P. T.; Cesar, C. L.; Chapman, S.; Charlton, M.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Humphries, A. J.; Hurt, J. L.; Hydomako, R.; Jonsell, S.; Madsen, N.; Menary, S.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; Silveira, D. M.; So, C.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.

    2011-01-01

    We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination.

  19. Directional excitation without breaking reciprocity

    NASA Astrophysics Data System (ADS)

    Ramezani, Hamidreza; Dubois, Marc; Wang, Yuan; Shen, Y. Ron; Zhang, Xiang

    2016-09-01

    We propose a mechanism for directional excitation without breaking reciprocity. This is achieved by embedding an impedance matched parity-time symmetric potential in a three-port system. The amplitude distribution within the gain and loss regions is strongly influenced by the direction of the incoming field. Consequently, the excitation of the third port is contingent on the direction of incidence while transmission in the main channel is immune. Our design improves the four-port directional coupler scheme, as there is no need to implement an anechoic termination to one of the ports.

  20. Decentralized nonlinear optimal excitation control

    SciTech Connect

    Lu, Q.; Sun, Y.; Xu, Z.; Mochizuki, T.

    1996-11-01

    A design method to lay emphasis on differential geometric approach for decentralized nonlinear optimal excitation control of multimachine systems is suggested in this paper. The control law achieved is implemented via purely local measurements. Moreover, it is independent of the parameters of power networks. Simulations are performed on a six-machine system. It has been demonstrated that the nonlinear optimal excitation control could adapt to the conditions under large disturbances. Besides, this paper has verified that the optimal control in the sense of LQR principle for the linearized system is equivalent to an optimal control in the sense of a quasi-quadratic performance index for the primitive nonlinear control system.