NASA Astrophysics Data System (ADS)
Foltynowicz, Robert J.; Robinson, Jason D.; Grant, Edward R.
2001-03-01
We report the first high-resolution measurement of the adiabatic ionization potential of DCO and the fundamental bending frequency of DCO+. Fixing a first-laser frequency on selected ultraviolet transitions to individual rotational levels in the (000) band of the 3pπ 2Π intermediate Rydberg state of DCO, we scan a second visible laser over the range from 20 000 to 20 300 cm-1 to record double resonance photoionization efficiency (DR/PIE) spectra. Intermediate resonance with this Rydberg state facilitates transitions to the threshold for producing ground-state cations by bridging the Franck-Condon gap between the bent neutral radical and linear cation. By selecting a single rotational state for ionization, double-resonant excitation eliminates thermal congestion. Spectroscopic features for first-photon resonance are identified by reference to a complete assignment of the 3pπ 2Π(000)-X 2A'(000) band system of DCO. Calibration with HCO, for which the adiabatic ionization threshold is accurately known, establishes an experimental instrument function that accounts for collisional effects on the shape of the photoionization efficiency spectrum near threshold. Analysis of the DR/PIE threshold for DCO yields an adiabatic ionization threshold of 65 616±3 cm-1. By extrapolation of vibrationally autoionizing Rydberg series accessed from the Σ+ component of the 3pπ 2Π(010) intermediate state, we determine an accurate rotationally state-resolved threshold for producing DCO+(010). This energy, together with the threshold determined for the vibrational ground state of the cation provides a first estimate of the bending frequency for DCO+ as 666±3 cm-1. Assignment of the (010) autoionization spectrum further yields a measurement of an energy of 4.83±0.01 cm-1 for the (2-1) rotational transition in the 1Σ+(0110) state of DCO+.
NASA Astrophysics Data System (ADS)
Trushin, Egor; Betzinger, Markus; Blügel, Stefan; Görling, Andreas
2016-08-01
An approach to calculate fundamental band gaps, ionization energies, and electron affinities of periodic electron systems is explored. Starting from total energies obtained with the help of the adiabatic-connection fluctuation-dissipation (ACFD) theorem, these physical observables are calculated according to their basic definition by differences of the total energies of the N -, (N -1 ) -, and (N +1 ) -electron system. The response functions entering the ACFD theorem are approximated here by the direct random phase approximation (dRPA). For a set of prototypical semiconductors and insulators it is shown that even with this quite drastic approximation the resulting band gaps are very close to experiment and of a similar quality to those from the computationally more involved G W approximation. By going beyond the dRPA in the future the accuracy of the calculated band gaps may be significantly improved further.
Delgado, Juan C; Selsby, Ronald G
2013-01-01
The ground state configuration of the gas phase cationic dyes pinacyanol chloride and rhodamine B are optimized with HF/6-311 + G(2d,2p) method and basis set. B3PW91/6-311 + G(2df,2p) functional and basis set is used to calculate the Mulliken atom charge distribution, total molecular energy, the dipole moment, the vertical ionization potential, the adiabatic electron affinity and the lowest excited triplet state, the last three as an energy difference between separately calculated open shell and ground states. The triplet and extra electron states are optimized to find the relaxation energy. In the ground state optimization of both dyes the chloride anion migrates to a position near the center of the chromophore. For rhodamine B the benzoidal group turns perpendicular to the chromophore plane. For both dyes, the LUMO is mostly of π character associated with the aromatic part of the molecule containing the chromophore. The highest occupied MOs consist of three almost degenerate eigenvectors involving the chloride anion coordinated with σ electrons in the molecular framework. The fourth highest MO is of π character. For both molecules in the gas phase ionization process the chloride anion loses the significant fraction of electric charge. In electron capture, the excess charge goes mainly on the dye cation. PMID:22891949
Wilken, F.; Bauer, D.
2006-11-17
The ionization of a one-dimensional model helium atom in short laser pulses using time-dependent density-functional theory is investigated. We calculate ionization probabilities as a function of laser intensity by approximating the correlation function of the system adiabatically with an explicit dependence on the fractional number of bound electrons. For the correlation potential we take the derivative discontinuity at integer numbers of bound electrons explicitly into account. This approach reproduces ionization probabilities from the solution of the time-dependent Schroedinger equation, in particular, the so-called knee due to nonsequential ionization.
Adiabatic Hyperspherical Analysis of Realistic Nuclear Potentials
NASA Astrophysics Data System (ADS)
Daily, K. M.; Kievsky, Alejandro; Greene, Chris H.
2015-12-01
Using the hyperspherical adiabatic method with the realistic nuclear potentials Argonne V14, Argonne V18, and Argonne V18 with the Urbana IX three-body potential, we calculate the adiabatic potentials and the triton bound state energies. We find that a discrete variable representation with the slow variable discretization method along the hyperradial degree of freedom results in energies consistent with the literature. However, using a Laguerre basis results in missing energy, even when extrapolated to an infinite number of basis functions and channels. We do not include the isospin T = 3/2 contribution in our analysis.
Ionization potentials of seaborgium
Johnson, E.; Pershina, V.; Fricke, B.
1999-10-21
Multiconfiguration relativistic Dirac-Fock values were calculated for the first six ionization potentials of seaborgium and of the other group 6 elements. No experimental ionization potentials are available for seaborgium. Accurate experimental values are not available for all of the other ionization potentials. Ionic radii for the 4+ through 6+ ions of seaborgium are also presented. The ionization potentials and ionic radii obtained will be used to predict some physiochemical properties of seaborgium and its compounds.
Theoretical determinations of ionization potentials of dopamine
NASA Astrophysics Data System (ADS)
Lu, J. F.; Yu, Z. Y.
2013-04-01
Adiabatic and vertical ionization potentials (IPs) of nine conformers of dopamine in the gas phase are determined using density functional theory (DFT) B3LYP, B3P86, B3PW91 methods and high level ab initio HF method with 6-311++G** basis set, respectively. And the nine stable cationic states have been found in the ionization process of dopamine. Vertical ionization potentials of nine conformers of dopamine are calculated using the older outer-valence Green's function (OVGF) calculations at 6-311++G** basis set. Vibrational frequencies and infrared spectrum intensities of G1b and G1b+ at B3LYP/6-311++G** level are discussed.
NASA Astrophysics Data System (ADS)
Hofmann, C.; Zimmermann, T.; Zielinski, A.; Landsman, A. S.
2016-04-01
The validity of the adiabatic approximation in strong field ionization under typical experimental conditions has recently become a topic of great interest. Experimental results have been inconclusive, in part, due to the uncertainty in experimental calibration of intensity. Here we turn to the time-dependent Schrödinger equation, where all the laser parameters are known exactly. We find that the centre of the electron momentum distribution (typically used for calibration of elliptically and circularly polarized light) is sensitive to non-adiabatic effects, leading to intensity shifts in experimental data that can significantly affect the interpretation of results. On the other hand, the transverse momentum spread in the plane of polarization is relatively insensitive to such effects, even in the Keldysh parameter regime approaching γ ≈ 3. This suggests the transverse momentum spread in the plane of polarization as a good alternative to the usual calibration method, particularly for experimental investigation of non-adiabatic effects using circularly polarized light.
The lowest ionization potentials of Al2
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Barnes, Leslie A.; Taylor, Peter R.
1988-01-01
Potential curves for the lowest two electronic states (X 2 sigma g + and A 2 pi u) of Al2(+) were computed using complete active space SCF/multireference CI wave functions and large Gaussian basis sets. The lowest observable vertical ionization potential (to Al2(+) X 2 sigma g +) of the Al2 X 3 pi u ground state is calculated to occur around 6.1 eV, in excellent agreement with the experimental range of 6.0 to 6.42 eV obtained in recent cluster ionization studies by Cox and co-workers. The second vertical ionization potential (to Al2(+) A 2 pi u) occurs near 6.4 eV, also within the experimental range. The adiabatic IP of 5.90 eV is in good agreement with the value of 5.8 to 6.1 eV deduced by Hanley and co-workers from the difference in thresholds between collision induced dissociation processes of Al3(+). The computed IP values are somewhat larger than those deduced from branching ratios in cluster fragmentation experiments by Jarrold and co-workers. The observation of an ionization threshold below 6.42 eV is shown to be incompatible with an Al2 ground electronic state assignment of 3 sigma g -, but the separation between the two lowest states of Al2 is so small that it is likely that both are populated in the experiments, so that this does not provide unambiguous support for the recent theoretical assignment of the ground state as 3 pi u.
Trapping ultracold atoms in a time-averaged adiabatic potential
Gildemeister, M.; Nugent, E.; Sherlock, B. E.; Kubasik, M.; Sheard, B. T.; Foot, C. J.
2010-03-15
We report an experimental realization of ultracold atoms confined in a time-averaged, adiabatic potential (TAAP). This trapping technique involves using a slowly oscillating ({approx}kHz) bias field to time-average the instantaneous potential given by dressing a bare magnetic potential with a high-frequency ({approx}MHz) magnetic field. The resultant potentials provide a convenient route to a variety of trapping geometries with tunable parameters. We demonstrate the TAAP trap in a standard time-averaged orbiting potential trap with additional Helmholtz coils for the introduction of the radio frequency dressing field. We have evaporatively cooled 5x10{sup 4} atoms of {sup 87}Rb to quantum degeneracy and observed condensate lifetimes of longer than 3 s.
Ionization Potentials for Isoelectronic Series.
ERIC Educational Resources Information Center
Agmon, Noam
1988-01-01
Presents a quantitative treatment of ionization potentials of isoelectronic atoms. By looking at the single-electron view of calculating the total energy of an atom, trends in the screening and effective quantum number parameters are examined. Approaches the question of determining electron affinities. (CW)
On the ionization potential of molecular oxygen
NASA Technical Reports Server (NTRS)
Samson, J. A. R.; Gardner, J. L.
1974-01-01
The ionization potential of O2 was measured by the technique of high resolution photoelectron spectroscopy taking into account the influence of rotational structure on the shape of the vibrational bands. A value of 12.071 + or - .001 eV (1027.1 + or - 0.1 A) was found for the ionization potential. A lowering of the ionization potential caused by a branch-head when delta N = -2 gave an appearance potential for ionization of 12.068 + or - .001 eV (1027.4 + or - 0.1 A).
Thermochromic behaviors and ionization potentials of organopolysilanes
NASA Astrophysics Data System (ADS)
Yokoyama, Kenji; Yokoyama, Masaaki
1989-04-01
Ionization potentials of organopolysilanes with different kinds of substituents were evaluated from the low energy photo-electron emission measurements in air. An aryl-substituted organopolysilane capable of σ - π mixing between Si backbone σ and side-group π electrons gave smaller ionization potential by about 0.1˜0.15 eV compared with alkyl-substituted organopolysilanes. The value of ionization potentials in some alkyl-substituted organopolysilanes which showed thermochromic behaviors was found to vary substantially with thermally induced reversible changes in polymer backbone conformation, indicating that the effective conjugation length of σ electrons decreases above the thermochromic transition temperature.
Geometric phase of an atom inside an adiabatic radio-frequency potential
Zhang, P.; You, L.
2007-09-15
We investigate the geometric phase of an atom inside an adiabatic radio-frequency (rf) potential created from a static magnetic field (B field) and a time-dependent rf field. The spatial motion of the atomic center of mass is shown to give rise to a geometric phase, or Berry's phase, in the adiabatically evolving atomic hyperfine spin along the local B field. This phase is found to depend on both the static B field along the semiclassical trajectory of the atomic center of mass and an effective magnetic field consisting of the total B field, including the oscillating rf field. Specific calculations are provided for several recent atom interferometry experiments and proposals utilizing adiabatic rf potentials.
NASA Astrophysics Data System (ADS)
Agostini, Federica; Abedi, Ali; Suzuki, Yasumitsu; Min, Seung Kyu; Maitra, Neepa T.; Gross, E. K. U.
2015-03-01
The Born-Oppenheimer (BO) approximation allows to visualize the coupled electron-nuclear dynamics in molecular systems as a set of nuclei moving on a single potential energy surface representing the effect of the electrons in a given eigenstate. Many interesting phenomena, however, such as vision or charge separation in organic photovoltaic materials, take place in conditions beyond its range of validity. Nevertheless, the basic construct of the adiabatic treatment, the BO potential energy surfaces, is employed to describe non-adiabatic processes and the full problem is represented in terms of adiabatic states and transitions among them in regions of strong non-adiabatic coupling. But the concept of single potential energy is lost. The alternative point of view arising in the framework of the exact factorization of the electron-nuclear wave function will be presented. A single, time-dependent, potential energy provides the force driving the nuclear motion and is adopted as starting point for the development of quantum-classical approximations to the full quantum mechanical problem.
Ionization of the hydrogen atom in strong magnetic fields. Beyond the adiabatic approximation.
NASA Astrophysics Data System (ADS)
Potekhin, A. Y.; Pavlov, G. G.; Ventura, J.
1997-01-01
High magnetic fields in neutron stars, B~10^11^-10^13^G, substantially modify the properties of atoms and their interaction with radiation. In particular, the photoionization cross section becomes anisotropic and polarization dependent, being strongly reduced when the radiation is polarized perpendicular to the field. In a number of previous works based on the adiabatic approximation the conclusion was drawn that this transverse cross section vanishes for frequencies ω smaller than the electron cyclotron frequency ω_c_=eB/(m_e_c). In other works (which employed a different form of the interaction operator) appreciable finite values were obtained, ~σ_0gamma^-1^ near the photoionization threshold, where σ_0_ is the cross section without magnetic field, and γ=B/(2.35x10^9^G). Since it is the transverse cross section which determines the properties of radiation emitted from neutron star atmospheres, an adequate interpretation of the neutron star thermal-like radiation requires a resolution of this controversy. In the present work we calculate the atomic wave functions for both discrete and continuum states by solving the coupled channel equations allowing the admixture between different Landau levels, which provides much higher accuracy than the adiabatic approximation. This enables us to resolve the above contradiction in favour of the finite transverse cross sections at ω<ω_c_. Moreover, for any form of the interaction operator the non-adiabatic corrections appear to be substantial for frequencies ω> 0.3ω_c_. The non-adiabatic treatment of the continuum includes coupling between closed and open channels, which leads to the autoionization of quasi-bound energy levels associated with the electron cyclotron (Landau) excitations and gives rise to Beutler-Fano resonances of the photoionization cross section. We calculate the autoionization widths of these quasi-bound levels and compare them with the radiative widths. The correlation of the open channels is
Dressed adiabatic and diabatic potentials to study conical intersections for F + H2
NASA Astrophysics Data System (ADS)
Das, Anita; Sahoo, Tapas; Mukhopadhyay, Debasis; Adhikari, Satrajit; Baer, Michael
2012-02-01
We follow a suggestion by Lipoff and Herschbach [Mol. Phys. 108, 1133 (2010), 10.1080/00268971003662912] and compare dressed and bare adiabatic potentials to get insight regarding the low-energy dynamics (e.g., cold reaction) taking place in molecular systems. In this particular case, we are interested to study the effect of conical intersections (ci) on the interacting atoms. For this purpose, we consider vibrational dressed adiabatic and vibrational dressed diabatic potentials in the entrance channel of reactive systems. According to our study, the most one should expect, in case of F + H2, is a mild effect of the (1, 2) ci on its reactive/exchange process-an outcome also supported by experiment. This happens although the corresponding dressed and bare potential barriers (and the corresponding van der Waals potential wells) differ significantly from each other.
Femtosecond Laser Ionization of Organic Amines with Very Low Ionization Potential.
NASA Astrophysics Data System (ADS)
Yatsuhashi, Tomoyuki; Obayashi, Takashi; Tanaka, Michinori; Murakami, Masanao; Nakashima, Nobuaki
2006-03-01
The interaction between high intensity femtosecond laser and molecules is one of the most attractive areas in laser chemistry and ionization is the most fundamental subject. Theoretical consideration successfully reproduced the ionization behavior of rare gases. However, the understanding of ionization mechanisms of large molecules is difficult more than those of rare gases due to their complexity. Generally speaking, molecules are harder to ionize than rare gases even if they have the same ionization potential. The suppressed ionization phenomena are one of the important features of molecular ionization. Hankin et al. examined 23 organic molecules with ionization potentials between 8.25 and 11.52 eV. We have examined ionization and/ or fragmentation of many organic molecules, including aromatic compounds, halogenated compounds, methane derivatives etc. at various wavelengths below 10^16 Wcm-2. In order to investigate the nature of molecular ionization, it is interesting to examine a variety of molecule in a wide range of ionization potential. In this study, we examined several organic amines because we can explore the uninvestigated ionization potential range down to 5.95 eV. In addition to the significant suppression of the ionization rates, stepwise ionization behavior, which was not observed in rare gases, was observed.
CVRQD ab initio ground-state adiabatic potential energy surfaces for the water molecule.
Barletta, Paolo; Shirin, Sergei V; Zobov, Nikolai F; Polyansky, Oleg L; Tennyson, Jonathan; Valeev, Edward F; Császár, Attila G
2006-11-28
The high accuracy ab initio adiabatic potential energy surfaces (PESs) of the ground electronic state of the water molecule, determined originally by Polyansky et al. [Science 299, 539 (2003)] and called CVRQD, are extended and carefully characterized and analyzed. The CVRQD potential energy surfaces are obtained from extrapolation to the complete basis set of nearly full configuration interaction valence-only electronic structure computations, augmented by core, relativistic, quantum electrodynamics, and diagonal Born-Oppenheimer corrections. We also report ab initio calculations of several quantities characterizing the CVRQD PESs, including equilibrium and vibrationally averaged (0 K) structures, harmonic and anharmonic force fields, harmonic vibrational frequencies, vibrational fundamentals, and zero-point energies. They can be considered as the best ab initio estimates of these quantities available today. Results of first-principles computations on the rovibrational energy levels of several isotopologues of the water molecule are also presented, based on the CVRQD PESs and the use of variational nuclear motion calculations employing an exact kinetic energy operator given in orthogonal internal coordinates. The variational nuclear motion calculations also include a simplified treatment of nonadiabatic effects. This sophisticated procedure to compute rovibrational energy levels reproduces all the known rovibrational levels of the water isotopologues considered, H(2) (16)O, H(2) (17)O, H(2) (18)O, and D(2) (16)O, to better than 1 cm(-1) on average. Finally, prospects for further improvement of the ground-state adiabatic ab initio PESs of water are discussed. PMID:17144700
Kutzelnigg, Werner; Jaquet, Ralph
2006-11-15
After a short historical account of the theory of the H3+ ion, two ab initio methods are reviewed that allow the computation of the ground-state potential energy surface (PES) of H3+ in the Born-Oppenheimer (BO) approximation, with microhartree or even sub-microhartree accuracy, namely the R12 method and the method of explicitly correlated Gaussians. The BO-PES is improved by the inclusion of relativistic effects and adiabatic corrections. It is discussed how non-adiabatic effects on rotation and vibration can be simulated by corrections to the moving nuclear masses. The importance of the appropriate analytic fit to the computed points of the PES for the subsequent computation of the rovibronic spectrum is addressed. Some recent extensions of the computed PES in the energy region above the barrier to linearity are reviewed. This involves a large set of input geometries and the correct treatment of the dissociation asymptotics, including the coupling with the first excited singlet state. Some comments on this state as well as on the lowest triplet state of H3+ are made. The paper ends with a few remarks on the ion H5+. PMID:17015373
Time-Averaged Adiabatic Potentials: Versatile Matter-Wave Guides and Atom Traps
NASA Astrophysics Data System (ADS)
Lesanovsky, Igor; von Klitzing, Wolf
2007-08-01
We demonstrate a novel class of trapping potentials, time-averaged adiabatic potentials (TAAP), which allows the generation of a large variety of traps for quantum gases and matter-wave guides for atom interferometers. Examples include stacks of pancakes, rows of cigars, and multiple rings or sickles. The traps can be coupled through controllable tunneling barriers or merged altogether. We present analytical expressions for pancake-, cigar-, and ring-shaped traps. The ring geometry is of particular interest for guided matter-wave interferometry as it provides a perfectly smooth waveguide of widely tunable diameter and thus adjustable sensitivity of the interferometer. The flexibility of the TAAP would make possible the use of Bose-Einstein condensates as coherent matter waves in large-area atom interferometers.
Time-averaged adiabatic potentials: versatile matter-wave guides and atom traps.
Lesanovsky, Igor; von Klitzing, Wolf
2007-08-24
We demonstrate a novel class of trapping potentials, time-averaged adiabatic potentials (TAAP), which allows the generation of a large variety of traps for quantum gases and matter-wave guides for atom interferometers. Examples include stacks of pancakes, rows of cigars, and multiple rings or sickles. The traps can be coupled through controllable tunneling barriers or merged altogether. We present analytical expressions for pancake-, cigar-, and ring-shaped traps. The ring geometry is of particular interest for guided matter-wave interferometry as it provides a perfectly smooth waveguide of widely tunable diameter and thus adjustable sensitivity of the interferometer. The flexibility of the TAAP would make possible the use of Bose-Einstein condensates as coherent matter waves in large-area atom interferometers. PMID:17930945
Time-Averaged Adiabatic Potentials: Versatile Matter-Wave Guides and Atom Traps
Lesanovsky, Igor; Klitzing, Wolf von
2007-08-24
We demonstrate a novel class of trapping potentials, time-averaged adiabatic potentials (TAAP), which allows the generation of a large variety of traps for quantum gases and matter-wave guides for atom interferometers. Examples include stacks of pancakes, rows of cigars, and multiple rings or sickles. The traps can be coupled through controllable tunneling barriers or merged altogether. We present analytical expressions for pancake-, cigar-, and ring-shaped traps. The ring geometry is of particular interest for guided matter-wave interferometry as it provides a perfectly smooth waveguide of widely tunable diameter and thus adjustable sensitivity of the interferometer. The flexibility of the TAAP would make possible the use of Bose-Einstein condensates as coherent matter waves in large-area atom interferometers.
Ab initio adiabatic and diabatic potential-energy curves of the LiH molecule
NASA Astrophysics Data System (ADS)
Boutalib, A.; Gadéa, F. X.
1992-07-01
For nearly all states below the ionic limit [i.e., Li(2s, 2p, 3s, 3p, 3d, 4s, and 4p)+H] we perform the first adiabatic and diabatic studies. This treatment involves a nonempirical pseudopotential for Li and a full configuration-interaction treatment of the valence-electron system. Core-valence correlation is taken into account according to a core-polarization-potential method. We present an analysis of the diabatic curves and introduce appropriate small corrections accounting for basis-set limitations. For the low-lying states, our vibrational level spacings and spectroscopic constants are in excellent agreement with the available experimental data and with the best all-electron results. Experimental suggestions are given for the higher states.
Diffusion of a massive particle in a periodic potential: Application to adiabatic ratchets
NASA Astrophysics Data System (ADS)
Rozenbaum, Viktor M.; Makhnovskii, Yurii A.; Shapochkina, Irina V.; Sheu, Sheh-Yi; Yang, Dah-Yen; Lin, Sheng Hsien
2015-12-01
We generalize a theory of diffusion of a massive particle by the way in which transport characteristics are described by analytical expressions that formally coincide with those for the overdamped massless case but contain a factor comprising the particle mass which can be calculated in terms of Risken's matrix continued fraction method (MCFM). Using this generalization, we aim to elucidate how large gradients of a periodic potential affect the current in a tilted periodic potential and the average current of adiabatically driven on-off flashing ratchets. For this reason, we perform calculations for a sawtooth potential of the period L with an arbitrary sawtooth length (l
Diffusion of a massive particle in a periodic potential: Application to adiabatic ratchets.
Rozenbaum, Viktor M; Makhnovskii, Yurii A; Shapochkina, Irina V; Sheu, Sheh-Yi; Yang, Dah-Yen; Lin, Sheng Hsien
2015-12-01
We generalize a theory of diffusion of a massive particle by the way in which transport characteristics are described by analytical expressions that formally coincide with those for the overdamped massless case but contain a factor comprising the particle mass which can be calculated in terms of Risken's matrix continued fraction method (MCFM). Using this generalization, we aim to elucidate how large gradients of a periodic potential affect the current in a tilted periodic potential and the average current of adiabatically driven on-off flashing ratchets. For this reason, we perform calculations for a sawtooth potential of the period L with an arbitrary sawtooth length (l
Ruscic, B.; Litorja, M.; Chemistry
2000-01-07
A new upper limit to the adiabatic ionization energy of trans-hydroxyoxomethyl, EI(t-HOCO){<=}8.195{+-}0.022 eV, is provided, producing a lower limit to the enthalpy of formation, {Delta}H{sub f 0}{sup o}(t-HOCO){>=}-45.8{+-}0.7 kcal/mol ({>=}-46.5{+-}0.7 kcal/mol at 298 K). The spectrum shows progressions in C{double_bond}O and C-O stretches of HOCO{sup +} and provides evidence for the excitation of OCO bend. In addition, the data tentatively suggest an ionization onset as low as 8.06{+-}0.03 eV. While it is not clear whether the latter corresponds to cis or trans isomer, it may indicate that {Delta}H{sub f 0}{sup o}(HOCO) is even higher.
Rotational excitation of H2O by para-H2 from an adiabatically reduced dimensional potential
NASA Astrophysics Data System (ADS)
Scribano, Yohann; Faure, Alexandre; Lauvergnat, David
2012-03-01
Cross sections and rate coefficients for low lying rotational transitions in H2O colliding with para-hydrogen pH2 are computed using an adiabatic approximation which reduces the dimensional dynamics from a 5D to a 3D problem. Calculations have been performed at the close-coupling level using the recent potential of Valiron et al. [J. Chem. Phys. 129, 134306 (2008), 10.1063/1.2988314]. A good agreement is found between the reduced adiabatic calculations and the 5D exact calculations, with an impressive time saving and memory gain. This adiabatic reduction of dimensionality seems very promising for scattering studies involving the excitation of a heavy target molecule by a light molecular projectile.
NASA Astrophysics Data System (ADS)
Hadinger, G.; Tergiman, Y. S.
1986-12-01
From isotopic spectroscopic data, the internuclear distance dependence of the adiabatic corrections to the potential energy curve has been determined for the ∑ state of a diatomic molecule. Starting from an analytic inversion procedure previously described, the adiabatic corrections can be found in a straightforward way, provided that they can be considered as perturbing terms of the vibration-rotation wave equation. Application to the case of the X 1∑+ state of the lithium hydrides 6LiH, 7LiH, 6LiD, and 7LiD is carried out. The adiabatic corrections ΔUH(R) and ΔULi(R) are obtained and compared with recent results.
Self-consistent calculation of hyperfine fields and adiabatic potential of impurities in iron
NASA Astrophysics Data System (ADS)
Kanamori, Junjiro; Akai, Hisazumi; Akai, Masako
1984-01-01
Hyperfine fields of impurities of the atomic number Z=1 56 at the substitutional site and those of light impurities of Z=1 9 at the interstitial sites in ferromagnetic iron are calculated by the KKR method adapted to the system containing a single impurity atom. The potential of the impurity atom is determined self-consistently by use of the local spin density functional formalism. The results for nonmagnetic sp valence impurities agree with those of the previous nonself-consistent calculation by Katayama-Yoshida, Terakura and Kanamori except for a few cases, confirming their theory of the systematic variation of hyperfine fields. The calculation for magnetic impurities of transition elements is presented for the first time in this paper. The calculations mentioned so far assume that impurities are situated at the center of each site. For the purpose of discussing the stability of the impurity positions, the change of the adiabatic potential due to displacements from the center is calculated by carrying out similar self-consistent calculations for off-center impurity positions. It is concluded that positive muon and some light impurities including boron will be displaced from the center when trapped in a vacancy.
Measurement of the first ionization potential of astatine by laser ionization spectroscopy
NASA Astrophysics Data System (ADS)
Rothe, S.; Andreyev, A. N.; Antalic, S.; Borschevsky, A.; Capponi, L.; Cocolios, T. E.; de Witte, H.; Eliav, E.; Fedorov, D. V.; Fedosseev, V. N.; Fink, D. A.; Fritzsche, S.; Ghys, L.; Huyse, M.; Imai, N.; Kaldor, U.; Kudryavtsev, Yuri; Köster, U.; Lane, J. F. W.; Lassen, J.; Liberati, V.; Lynch, K. M.; Marsh, B. A.; Nishio, K.; Pauwels, D.; Pershina, V.; Popescu, L.; Procter, T. J.; Radulov, D.; Raeder, S.; Rajabali, M. M.; Rapisarda, E.; Rossel, R. E.; Sandhu, K.; Seliverstov, M. D.; Sjödin, A. M.; van den Bergh, P.; van Duppen, P.; Venhart, M.; Wakabayashi, Y.; Wendt, K. D. A.
2013-05-01
The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine.
Measurement of the first ionization potential of astatine by laser ionization spectroscopy
Rothe, S.; Andreyev, A. N.; Antalic, S.; Borschevsky, A.; Capponi, L.; Cocolios, T. E.; De Witte, H.; Eliav, E.; Fedorov, D. V.; Fedosseev, V. N.; Fink, D. A.; Fritzsche, S.; Ghys, L.; Huyse, M.; Imai, N.; Kaldor, U.; Kudryavtsev, Yuri; Köster, U.; Lane, J. F. W.; Lassen, J.; Liberati, V.; Lynch, K. M.; Marsh, B. A.; Nishio, K.; Pauwels, D.; Pershina, V.; Popescu, L.; Procter, T. J.; Radulov, D.; Raeder, S.; Rajabali, M. M.; Rapisarda, E.; Rossel, R. E.; Sandhu, K.; Seliverstov, M. D.; Sjödin, A. M.; Van den Bergh, P.; Van Duppen, P.; Venhart, M.; Wakabayashi, Y.; Wendt, K. D. A.
2013-01-01
The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine. PMID:23673620
Measurement of the first ionization potential of astatine by laser ionization spectroscopy.
Rothe, S; Andreyev, A N; Antalic, S; Borschevsky, A; Capponi, L; Cocolios, T E; De Witte, H; Eliav, E; Fedorov, D V; Fedosseev, V N; Fink, D A; Fritzsche, S; Ghys, L; Huyse, M; Imai, N; Kaldor, U; Kudryavtsev, Yuri; Köster, U; Lane, J F W; Lassen, J; Liberati, V; Lynch, K M; Marsh, B A; Nishio, K; Pauwels, D; Pershina, V; Popescu, L; Procter, T J; Radulov, D; Raeder, S; Rajabali, M M; Rapisarda, E; Rossel, R E; Sandhu, K; Seliverstov, M D; Sjödin, A M; Van den Bergh, P; Van Duppen, P; Venhart, M; Wakabayashi, Y; Wendt, K D A
2013-01-01
The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine. PMID:23673620
Determination of the first ionization potential of actinium
NASA Astrophysics Data System (ADS)
Roßnagel, J.; Raeder, S.; Hakimi, A.; Ferrer, R.; Trautmann, N.; Wendt, K.
2012-01-01
Using resonance ionization spectroscopy the first-ionization potential of actinium has been determined by analyzing different Rydberg series in two-color resonant laser excitation. Three individual Rydberg series were investigated, converging toward the ionic ground state and toward the first- and second-excited state of the actinium ion, respectively. A combined analysis of the convergence limits leads to a consistent value for the first-ionization potential of Ac of 43394.45(19)cm-1, equivalent to 5.380226(24) eV.
Ionizing potential waves and high-voltage breakdown streamers.
NASA Technical Reports Server (NTRS)
Albright, N. W.; Tidman, D. A.
1972-01-01
The structure of ionizing potential waves driven by a strong electric field in a dense gas is discussed. Negative breakdown waves are found to propagate with a velocity proportional to the electric field normal to the wavefront. This causes a curved ionizing potential wavefront to focus down into a filamentary structure, and may provide the reason why breakdown in dense gases propagates in the form of a narrow leader streamer instead of a broad wavefront.
Determination of the first ionization potential of technetium
Mattolat, C.; Gottwald, T.; Raeder, S.; Rothe, S.; Schwellnus, F.; Wendt, K.; Thoerle-Pospiech, P.; Trautmann, N.
2010-05-15
The first ionization potential (IP) of technetium (Tc) has been determined by evaluating Rydberg convergences toward the first ionization potential as well as toward two low-lying excited states of the singly charged Tc ion. The Rydberg states were excited and detected by applying multiphoton resonance ionization mass spectrometry (RIMS) on the long-lived isotope {sup 99g}Tc using a three-color excitation scheme. The observed Rydberg convergences yield a result for the first ionization potential of Tc V{sub IP}(Tc)=7.119380(32) eV. This precise value for V{sub IP}(Tc) is somewhat lower than the so far published data of 7.23 eV or 7.28 eV, dating back to the 1950s.
NASA Astrophysics Data System (ADS)
Kato, Tsuyoshi; Ide, Yoshihiro; Yamanouchi, Kaoru
2015-12-01
We first calculate the ground-state molecular wave function of 1D model H2 molecule by solving the coupled equations of motion formulated in the extended multi-configuration time-dependent Hartree-Fock (MCTDHF) method by the imaginary time propagation. From the comparisons with the results obtained by the Born-Huang (BH) expansion method as well as with the exact wave function, we observe that the memory size required in the extended MCTDHF method is about two orders of magnitude smaller than in the BH expansion method to achieve the same accuracy for the total energy. Second, in order to provide a theoretical means to understand dynamical behavior of the wave function, we propose to define effective adiabatic potential functions and compare them with the conventional adiabatic electronic potentials, although the notion of the adiabatic potentials is not used in the extended MCTDHF approach. From the comparison, we conclude that by calculating the effective potentials we may be able to predict the energy differences among electronic states even for a time-dependent system, e.g., time-dependent excitation energies, which would be difficult to be estimated within the BH expansion approach.
Kato, Tsuyoshi; Ide, Yoshihiro; Yamanouchi, Kaoru
2015-12-31
We first calculate the ground-state molecular wave function of 1D model H{sub 2} molecule by solving the coupled equations of motion formulated in the extended multi-configuration time-dependent Hartree-Fock (MCTDHF) method by the imaginary time propagation. From the comparisons with the results obtained by the Born-Huang (BH) expansion method as well as with the exact wave function, we observe that the memory size required in the extended MCTDHF method is about two orders of magnitude smaller than in the BH expansion method to achieve the same accuracy for the total energy. Second, in order to provide a theoretical means to understand dynamical behavior of the wave function, we propose to define effective adiabatic potential functions and compare them with the conventional adiabatic electronic potentials, although the notion of the adiabatic potentials is not used in the extended MCTDHF approach. From the comparison, we conclude that by calculating the effective potentials we may be able to predict the energy differences among electronic states even for a time-dependent system, e.g., time-dependent excitation energies, which would be difficult to be estimated within the BH expansion approach.
NASA Astrophysics Data System (ADS)
Fishman, S.; Soffer, A.
2016-07-01
We employ the recently developed multi-time scale averaging method to study the large time behavior of slowly changing (in time) Hamiltonians. We treat some known cases in a new way, such as the Zener problem, and we give another proof of the adiabatic theorem in the gapless case. We prove a new uniform ergodic theorem for slowly changing unitary operators. This theorem is then used to derive the adiabatic theorem, do the scattering theory for such Hamiltonians, and prove some classical propagation estimates and asymptotic completeness.
NASA Astrophysics Data System (ADS)
Yarkony, David
2015-03-01
The construction of fit single state potential energy surfaces (PESs), analytic representations of ab initio electronic energies and energy gradients, is now well established. These single state PESs, which are essential for accurate quantum dynamics and have found wide application in more approximate quasi-classical treatments, have revolutionized adiabatic dynamics. The situation for nonadiabatic processes involving dissociative and large amplitude motion is less sanguine. In these cases, compared to single electronic state dynamics, both the electronic structure data and the representation are more challenging to determine. We describe the recent development and applications of algorithms that enable description of multiple adiabatic electronic potential energy surfaces coupled by conical intersections in their full dimensionality using coupled quasi-diabatic states. These representations are demonstrably quasi-diabatic, provide accurate representations of conical intersection seams and can smooth out the discontinuities in electronic structure energies due to changing active orbital spaces that routinely afflict global multistate representations.
Schio, Luca; Alagia, Michele; Dias, Antonio A; Falcinelli, Stefano; Zhaunerchyk, Vitali; Lee, Edmond P F; Mok, Daniel K W; Dyke, John M; Stranges, Stefano
2016-07-14
In this work, hydrogen peroxide has been studied with threshold photoelectron (TPE) spectroscopy and photoelectron (PE) spectroscopy. The TPE spectrum has been recorded in the 10.0-21.0 eV ionization energy region, and the PE spectrum has been recorded at 21.22 eV photon energy. Five bands have been observed which have been assigned on the basis of UCCSD(T)-F12/VQZ-F12 and IP-EOM CCSD calculations. Vibrational structure has only been resolved in the TPE spectrum of the first band, associated with the X̃(2)Bg H2O2(+) ← X̃(1)A H2O2 ionization, on its low energy side. This structure is assigned with the help of harmonic Franck-Condon factor calculations that use the UCCSD(T)-F12a/VQZ-F12 computed adiabatic ionization energy (AIE), and UCCSD(T)-F12a/VQZ-F12 computed equilibrium geometric parameters and harmonic vibrational frequencies for the H2O2 X̃(1)A state and the H2O2(+) X̃(2)Bg state. These calculations show that the main vibrational structure on the leading edge of the first TPE band is in the O-O stretching mode (ω3) and the HOOH deformation mode (ω4), and comparison of the simulated spectrum to the experimental spectrum gives the first AIE of H2O2 as (10.685 ± 0.005) eV and ω4 = (850 ± 30) and ω3 = (1340 ± 30) cm(-1) in the X̃(2)Bg state of H2O2(+). Contributions from ionization of vibrationally excited levels in the torsion mode have been identified in the TPE spectrum of the first band and the need for a vibrationally resolved TPE spectrum from vibrationally cooled molecules, as well as higher level Franck-Condon factors than performed in this work, is emphasized. PMID:27045948
Inner-shell and double ionization potentials of aminophenol isomers.
Kryzhevoi, N. V.; Santra, R.; Cederbaum, L. S.
2011-01-01
A comprehensive study of single and double core ionization potentials of the aminophenol molecule is reported. The role of relaxation, correlation, relativistic, and basis set effects in these potentials is clarified. Special attention is paid to the isomer dependence of the single and double core ionization potentials. Some of them are also compared with the respective values of the phenol and aniline molecules. It is shown that the core level single ionization potentials of the para-, meta-, and ortho-aminophenol molecules differ only slightly from each other, rendering these structural isomers challenging to distinguish for conventional x-ray photoelectron spectroscopy. In contrast, the energy needed to remove two core electrons from different atoms depends noticeably on the mutual arrangement and even on the relative orientations of the hydroxyl and amine groups. Together with the electrostatic repulsion between the two core holes, relaxation effects accompanying double core ionization play a crucial role here. The pronounced sensitivity of the double ionization potentials, therefore, enables a spectroscopic characterization of the electronic structure of aminophenol isomers by means of x-ray two-photon photoelectron spectroscopy.
Beste, Ariana; Harrison, Robert J; Yanai, Takeshi
2006-01-01
Chemists are mainly interested in energy differences. In contrast, most quantum chemical methods yield the total energy which is a large number compared to the difference and has therefore to be computed to a higher relative precision than would be necessary for the difference alone. Hence, it is desirable to compute energy differences directly, thereby avoiding the precision problem. Whenever it is possible to find a parameter which transforms smoothly from an initial to a final state, the energy difference can be obtained by integrating the energy derivative with respect to that parameter (c.f., thermodynamic integration or adiabatic connection methods). If the dependence on the parameter is predominantly linear, accurate results can be obtained by single-point integration. In density functional theory (DFT) and Hartree-Fock, we applied the formalism to ionization potentials, excitation energies, and chemical bond breaking. Example calculations for ionization potentials and excitation energies showed that accurate results could be obtained with a linear estimate. For breaking bonds, we introduce a non-geometrical parameter which gradually turns the interaction between two fragments of a molecule on. The interaction changes the potentials used to determine the orbitals as well as constraining the orbitals to be orthogonal.
NASA Astrophysics Data System (ADS)
Beste, A.; Harrison, R. J.; Yanai, T.
2006-08-01
Chemists are mainly interested in energy differences. In contrast, most quantum chemical methods yield the total energy which is a large number compared to the difference and has therefore to be computed to a higher relative precision than would be necessary for the difference alone. Hence, it is desirable to compute energy differences directly, thereby avoiding the precision problem. Whenever it is possible to find a parameter which transforms smoothly from an initial to a final state, the energy difference can be obtained by integrating the energy derivative with respect to that parameter (cf. thermodynamic integration or adiabatic connection methods). If the dependence on the parameter is predominantly linear, accurate results can be obtained by single-point integration. In density functional theory and Hartree-Fock, we applied the formalism to ionization potentials, excitation energies, and chemical bond breaking. Example calculations for ionization potentials and excitation energies showed that accurate results could be obtained with a linear estimate. For breaking bonds, we introduce a nongeometrical parameter which gradually turns the interaction between two fragments of a molecule on. The interaction changes the potentials used to determine the orbitals as well as the constraint on the orbitals to be orthogonal.
NASA Astrophysics Data System (ADS)
George, D. X. F.; Kumar, Sanjay
2010-08-01
Ab initio global adiabatic as well as quasidiabatic potential energy surfaces for the ground and the first excited electronic states of the H + + CO system have been computed as a function of the Jacobi coordinates ( R, r, γ) using Dunning's cc-pVTZ basis set at the internally contracted multi-reference (single and double) configuration interaction level of accuracy. In addition, nonadiabatic coupling matrix elements arising from radial motion, mixing angle and coupling potential have been computed using the ab initio procedure [Simah et al. (1999) [66
NASA Astrophysics Data System (ADS)
Miyabe, Masabumi; Geppert, Christopher; Kato, Masaaki; Oba, Masaki; Wakaida, Ikuo; Watanabe, Kazuo; Wendt, Klaus D. A.
2006-03-01
High-resolution resonance ionization spectroscopy has been utilized to determine a precise ionization potential of Ca. Three-step resonance excitation with single-mode extended-cavity diode lasers populates long and unperturbed Rydberg series of 4snp (1P1) and 4snf (1F3) states in the range of n=20--150. Using an extended Ritz formula for quantum defects, the series convergence limit has been determined to be 49305.9240(20) cm-1 with the accuracy improved one order of magnitude higher than previously reported ones.
NASA Astrophysics Data System (ADS)
Haruyama, Jun; Suzuki, Takahiro; Hu, Chunping; Watanabe, Kazuyuki
2012-01-01
We present a simple and computationally efficient method to calculate excited-state nuclear forces on adiabatic potential-energy surfaces (APES) from linear-response time-dependent density-functional theory within a real-space framework. The Casida ansatz, which has been validated for computing first-order nonadiabatic couplings in previous studies, was applied to the calculation of the excited-state forces. Our method is validated by the consistency of results in the lower excited states, which reproduce well those obtained by the numerical derivative of each APES. We emphasize the usefulness of this technique by demonstrating the excited-state molecular-dynamics simulation.
NASA Astrophysics Data System (ADS)
Xavier, F. George D.; Kumar, Sanjay
2010-10-01
Ab initio global adiabatic and quasidiabatic potential energy surfaces of lowest four electronic (1-4 A3″) states of the H++O2 system have been computed in the Jacobi coordinates (R,r,γ) using Dunning's cc-pVTZ basis set at the internally contracted multireference (single and double) configuration interaction level of accuracy, which are relevant to the dynamics studies of inelastic vibrational and charge transfer processes observed in the scattering experiments. The computed equilibrium geometry parameters of the bound [HO2]+ ion in the ground electronic state and other parameters for the transition state for the isomerization process, HOO+⇌OOH+ are in good quantitative agreement with those available from the high level ab initio calculations, thus lending credence to the accuracy of the potential energy surfaces. The nonadiabatic couplings between the electronic states have been analyzed in both the adiabatic and quasidiabatic frameworks by computing the nonadiabatic coupling matrix elements and the coupling potentials, respectively. It is inferred that the dynamics of energy transfer processes in the scattering experiments carried out in the range of 9.5-23 eV would involve all the four electronic states.
NASA Astrophysics Data System (ADS)
Boogaarts, Maarten G. H.; Holleman, Iwan; Jongma, Rienk T.; Parker, David H.; Meijer, Gerard; Even, Uzi
1996-03-01
Doubly-resonant excitation/vibrational autoionization is used to accurately determine the ionization potential (IP) of the highly symmetric caged amine 1,4 diazabicyclo[2,2,2]octane (DABCO). The IP of DABCO excited with one quantum of the ν24(e') vibration lies at (59 048.62±0.03) cm-1, based on fitting 56 components of the npxy Rydberg series (δ=0.406±0.002) to the Rydberg formula. Rydberg state transition energies and linewidths are determined using standard calibration and linefitting techniques. The IP determined from Rydberg state extrapolation is compared with that determined by mass analyzed threshold ionization (MATI). Effects of static electric fields on MATI signals measured for the high Rydberg states are discussed.
Ionization potentials of small lithium clusters (Lin) and hydrogenated lithium clusters (LinH)
NASA Astrophysics Data System (ADS)
Wheeler, Steven E.; Schaefer, Henry F.
2005-05-01
We present accurate ionization potentials (IPs) for small lithium clusters and hydrogenated lithium clusters (n=1-4), computed using coupled-cluster singles and doubles theory augmented with a perturbative correction for connected triple excitations [CCSD(T)] with the correlation-consistent weighted core-valence quadruple-ζ basis set (cc-pwCVQZ). In some cases the full CCSDT method has been used. Comparison of computed binding energies with experiment for the pure cationic lithium clusters reveals excellent agreement, demonstrating that previous discrepancies between computed and experimentally derived atomization energies for the corresponding neutral clusters are due to the use of an inaccurate experimental IP for Li4. The experimental IP for Li4 falls 0.43eV below our theoretical adiabatic value of 4.74eV, which should be a lower bound to the measured IP. Our recommended zero-point corrected adiabatic IPs for Li, Li2, Li3, Li4, LiH, Li2H, Li3H, and Li4H are 5.39, 5.14, 4.11, 4.74, 7.69, 3.98, 4.69, and 4.05eV, respectively. Zero-point vibrationally corrected CCSD(T) atomization energies per atom for Li2+, Li3+, Li4+, LiH+, Li2H+, Li3H+, and Li4H+ are 0.64, 0.96, 0.90, 0.056, 1.62, 1.40, and 1.40eV, respectively.
Adiabatically driven Brownian pumps.
Rozenbaum, Viktor M; Makhnovskii, Yurii A; Shapochkina, Irina V; Sheu, Sheh-Yi; Yang, Dah-Yen; Lin, Sheng Hsien
2013-07-01
We investigate a Brownian pump which, being powered by a flashing ratchet mechanism, produces net particle transport through a membrane. The extension of the Parrondo's approach developed for reversible Brownian motors [Parrondo, Phys. Rev. E 57, 7297 (1998)] to adiabatically driven pumps is given. We demonstrate that the pumping mechanism becomes especially efficient when the time variation of the potential occurs adiabatically fast or adiabatically slow, in perfect analogy with adiabatically driven Brownian motors which exhibit high efficiency [Rozenbaum et al., Phys. Rev. E 85, 041116 (2012)]. At the same time, the efficiency of the pumping mechanism is shown to be less than that of Brownian motors due to fluctuations of the number of particles in the membrane. PMID:23944411
Close, David M; Crespo-Hernández, Carlos E; Gorb, Leonid; Leszczynski, Jerzy
2008-05-15
In a recent article we reported calculations of the ionization energy thresholds (IET) of microhydrated thymine (Close; et al. J. Phys. Chem. A, 2006, 110, 7485). Calculations showed a distinct effect of microhydration on the IET's of thymine. The first water molecule was seen to decrease the IET by about 0.1 eV, and the second and third water molecules caused a further decrease of less than 0.1 eV each. These changes in IET calculated for the canonical form of thymine with 1-3 waters of hydration are smaller than the experimental values determined by Kim et al. (J. Phys. Chem. C 1996, 100, 7933). In the present study it has been shown that there is considerable reorientation of the water molecules in microhydrated thymine upon ionization. This leads to the expectation that the experimental ionization energies may therefore represent an adiabatic process. The results presented here show that the changes in experimental ionization energies determined by Kim et al. for microhydrated thymine are in good agreement with the calculated adiabatic ionization energies. PMID:18402430
Ionization potential for excited S states of the lithium atom
Puchalski, M.; KePdziera, D.; Pachucki, K.
2010-12-15
Nonrelativistic, relativistic, quantum electrodynamic, and finite nuclear mass corrections to the energy levels are obtained for the nS{sub 1/2},n=3,...,9 states of the lithium atom. Computational approach is based on the explicitly correlated Hylleraas functions with the analytic integration and recursion relations. Theoretical predictions for the ionization potential of nS{sub 1/2} states and transition energies nS{sub 1/2{yields}}2S{sub 1/2} are compared to known experimental values for {sup 6,7}Li isotopes.
Ionization potential depression for non equilibrated aluminum plasmas
NASA Astrophysics Data System (ADS)
Calisti, A.; Ferri, S.; Talin, B.
2015-11-01
A classical molecular dynamics simulation model, designed to simulate neutral plasmas with various charge states of a given atom together with electrons, is used to investigate the ionization potential depression (IPD) in dense plasmas. The IPD is discussed for aluminum plasma at and out of equilibrium. The simulation results are compared with those of earlier theoretical models and with experimental data obtained in the framework of x-ray free-electron laser experiments. The model proposed in this work appears as an important tool to provide data for further discussion on IPD models.
Nonsequential double ionization of molecules
Prauzner-Bechcicki, Jakub S.; Sacha, Krzysztof; Zakrzewski, Jakub; Eckhardt, Bruno
2005-03-01
Double ionization of diatomic molecules by short linearly polarized laser pulses is analyzed. We consider the final stage of the ionization process, that is the decay of a highly excited two electron molecule, which is formed after rescattering. The saddles of the effective adiabatic potential energy close to which simultaneous escape of electrons takes place are identified. Numerical simulations of the ionization of molecules show that the process can be dominated by either sequential or nonsequential events. In order to increase the ratio of nonsequential to sequential ionizations very short laser pulses should be applied.
Magnetohydrodynamic Turbulence and the First Ionization Potential (FIP) Effect
NASA Astrophysics Data System (ADS)
Laming, J. Martin
2010-05-01
The FIP Effect is the elemental abundance anomaly observed in the solar corona and slow speed solar wind, whereby elements with First Ionization Potential (FIP) less than about 10 eV (e.g. Mg, Si, Fe) are enhanced in Elements with FIP higher than 10 eV (e.g. C, N, O) are essentially unchanged. This fractionation is assumed to occur in the solar chromosphere, since the low FIP elements are predominantly ionized here, while the high FIP elements are neutral. The abundance enhancement is currently explained by the upward action of the ponderomotive force on chromospheric ions, but not neutrals, as Alfven waves generated in the corona reflect from the steep chromospheric density gradients at each footpoint. The fractionation so produced is almost independent of ion mass as observed, and is stronger for closed coronal loops than for open field lines, also as observed. I will describe some recent results from models of the FIP effect, including the role of slow mode waves generated by the ponderomotive force of coherent Alfven waves in saturating the abundance enhancement. Work supported by NASA Contract NNGH05HL39I, and by basic research funds of the Office of Naval Research.
A plea for a reexamination of ionization potential depression measurements
NASA Astrophysics Data System (ADS)
Iglesias, Carlos A.
2014-09-01
Experiments at the Linac Coherent Light Source determined the ionization potential depression (IPD) in dense plasmas by measuring the Kα fluorescence associated with K-shell holes created by the X-ray free-electron laser. The analysis of the experimental spectrum found a significantly larger IPD than predicted by the widely used Stewart-Pyatt model. It is shown, however, that a more accurate treatment of atomic levels than used in the analysis has additional channels reducing the threshold laser energy for creating Kα photons without invoking an increase in the IPD. Thus, it is argued that a simulation of the Kα fluorescence using improved atomic data could impact the interpretation of the experimental results.
Assemblage of Superalkali Complexes with Ever Low-Ionization Potentials.
Paduani, C; Rappe, Andrew M
2016-08-18
A simple recipe is proposed for the obtention of new molecules with even lower vertical ionization potential (VIP): to decorate an atom of an electronegative element with superalkali species in number that exceeds its formal valence by one. For instance, density functional theory calculations show that by using the superalkali Li3O cluster (VIP = 3.83 eV) as building blocks decorating the O atom one obtains VIP = 3.33 eV for the Li9O4 cluster, which is lower than the calculated VIP for Cs (3.89 eV) and Li (5.39 eV). This feature is systematic, as confirmed by calculated results on Li-F and Li-S clusters as well. The calculated binding energy per atom of the large-sized species exceeds by far that of LiF (134.7 kcal/mol). PMID:27463269
Imaging cellular membrane potential through ionization of quantum dots
NASA Astrophysics Data System (ADS)
Rowland, Clare E.; Susumu, Kimihiro; Stewart, Michael H.; Oh, Eunkeu; Mäkinen, Antti J.; O'Shaughnessy, Thomas J.; Kushto, Gary; Wolak, Mason A.; Erickson, Jeffrey S.; Efros, Alexander L.; Huston, Alan L.; Delehanty, James B.
2016-03-01
Recent interest in quantum dots (QDs) stems from the plethora of potential applications that arises from their tunable absorption and emission profiles, high absorption cross sections, resistance to photobleaching, functionalizable surfaces, and physical robustness. The emergent use of QDs in biological imaging exploits these and other intrinsic properties. For example, quantum confined Stark effect (QCSE), which describes changes in the photoluminescence (PL) of QDs driven by the application of an electric field, provides an inherent means of detecting changes in electric fields by monitoring QD emission and thus points to a ready mean of imaging membrane potential (and action potentials) in electrically active cells. Here we examine the changing PL of various QDs subjected to electric fields comparable to those found across a cellular membrane. By pairing static and timeresolved PL measurements, we attempt to understand the mechanism driving electric-field-induced PL quenching and ultimately conclude that ionization plays a substantial role in initiating PL changes in systems where QCSE has traditionally been credited. Expanding on these findings, we explore the rapidity of response of the QD PL to applied electric fields and demonstrate changes amply able to capture the millisecond timescale of cellular action potentials.
NASA Technical Reports Server (NTRS)
Vidal, C. R.; Stwalley, W. C.
1982-01-01
The molecular constants and their adiabatic corrections have been determined for the (A 1 Sigma +) - (X 1 Sigma +) system of the isotopic lithium hydrides: (Li-6)H, (Li-7)H, (Li-6)D, and (Li-7)D. Using a fully quantum mechanical variational method, the potential energy curves (IPA potentials) are determined. Extending the variational method, we have obtained for the first time adiabatic corrections of potential energy curves from isotopic spectroscopic data. A significant difference between the potential energy curves of the lithium hydrides and the lithium deuterides has been observed. When Li-6 was replaced by Li-7, a significant difference was only observed for the (A 1 Sigma +) state, but not for the (X 1 Sigma +) state.
Topology of the Adiabatic Potential Energy Surfaces for theResonance States of the Water Anion
Haxton, Daniel J.; Rescigno, Thomas N.; McCurdy, C. William
2005-04-15
The potential energy surfaces corresponding to the long-lived fixed-nuclei electron scattering resonances of H{sub 2}O relevant to the dissociative electron attachment process are examined using a combination of ab initio scattering and bound-state calculations. These surfaces have a rich topology, characterized by three main features: a conical intersection between the {sup 2}A{sub 1} and {sup 2}B{sub 2} Feshbach resonance states; charge-transfer behavior in the OH ({sup 2}{Pi}) + H{sup -} asymptote of the {sup 2}B{sub 1} and {sup 2}A{sub 1} resonances; and an inherent double-valuedness of the surface for the {sup 2}B{sub 2} state the C{sub 2v} geometry, arising from a branch-point degeneracy with a {sup 2}B{sub 2} shape resonance. In total, eight individual seams of degeneracy among these resonances are located.
Monte Carlo simulations of ionization potential depression in dense plasmas
NASA Astrophysics Data System (ADS)
Stransky, M.
2016-01-01
A particle-particle grand canonical Monte Carlo model with Coulomb pair potential interaction was used to simulate modification of ionization potentials by electrostatic microfields. The Barnes-Hut tree algorithm [J. Barnes and P. Hut, Nature 324, 446 (1986)] was used to speed up calculations of electric potential. Atomic levels were approximated to be independent of the microfields as was assumed in the original paper by Ecker and Kröll [Phys. Fluids 6, 62 (1963)]; however, the available levels were limited by the corresponding mean inter-particle distance. The code was tested on hydrogen and dense aluminum plasmas. The amount of depression was up to 50% higher in the Debye-Hückel regime for hydrogen plasmas, in the high density limit, reasonable agreement was found with the Ecker-Kröll model for hydrogen plasmas and with the Stewart-Pyatt model [J. Stewart and K. Pyatt, Jr., Astrophys. J. 144, 1203 (1966)] for aluminum plasmas. Our 3D code is an improvement over the spherically symmetric simplifications of the Ecker-Kröll and Stewart-Pyatt models and is also not limited to high atomic numbers as is the underlying Thomas-Fermi model used in the Stewart-Pyatt model.
Paul, Amit Kumar; Ray, Somrita; Mukhopadhyay, Debasis; Adhikari, Satrajit
2011-07-21
We perform ab initio calculation using quantum chemistry package (MOLPRO) on the excited states of Na(3) cluster and present the adiabatic PESs for the electronic states 2(2)E' and 1(2)A(1)', and the non-adiabatic coupling (NAC) terms among those states. Since the ab initio calculated NAC elements for the states 2(2)E' and 1(2)A(1)' demonstrate the numerical validity of so called "Curl Condition," such states closely form a sub-Hilbert space. For this subspace, we employ the NAC terms to solve the "adiabatic-diabatic transformation (ADT)" equations to obtain the functional form of the transformation angles and pave the way to construct the continuous and single valued diabatic potential energy surface matrix by exploiting the existing first principle based theoretical means on beyond Born-Oppenheimer treatment. Nuclear dynamics has been carried out on those diabatic surfaces to reproduce the experimental spectrum for system B of Na(3) cluster and thereby, to explore the numerical validity of the theoretical development on beyond Born-Oppenheimer approach for adiabatic to diabatic transformation. PMID:21786987
Accurate ionization potential of semiconductors from efficient density functional calculations
NASA Astrophysics Data System (ADS)
Ye, Lin-Hui
2016-07-01
Despite its huge successes in total-energy-related applications, the Kohn-Sham scheme of density functional theory cannot get reliable single-particle excitation energies for solids. In particular, it has not been able to calculate the ionization potential (IP), one of the most important material parameters, for semiconductors. We illustrate that an approximate exact-exchange optimized effective potential (EXX-OEP), the Becke-Johnson exchange, can be used to largely solve this long-standing problem. For a group of 17 semiconductors, we have obtained the IPs to an accuracy similar to that of the much more sophisticated G W approximation (GWA), with the computational cost of only local-density approximation/generalized gradient approximation. The EXX-OEP, therefore, is likely as useful for solids as for finite systems. For solid surfaces, the asymptotic behavior of the vx c has effects similar to those of finite systems which, when neglected, typically cause the semiconductor IPs to be underestimated. This may partially explain why standard GWA systematically underestimates the IPs and why using the same GWA procedures has not been able to get an accurate IP and band gap at the same time.
Shapovalov, V A; Zhitlukhina, E S; Lamonova, K V; Shapovalov, V V; Rafailovich, M; Schwarz, S A; Jahoda, R; Reidy, V J; Orel, S M; Pashkevich, Yu G
2010-06-23
Spectroscopic investigations of a ZnAl(2)O(4) spinel doped with bivalent copper ions of 0.05% concentration have been carried out in the temperature range 4.2-290 K using a 3 cm(-1) range electron paramagnetic resonance (EPR) spectrometer having an operational frequency f = (9.241 ± 0.001) GHz. The spectrum can be represented as a superposition of two components: a low-temperature (LT) and a high-temperature (HT) one. Redistribution of integrated intensity between HT and LT components of the spectra occurs with temperature change that is typical of systems with multi-minimum adiabatic potential. Spectra observed are explained within the modified theory of crystalline field (MTCF). The electron levels of a Cu(2+) ion placed in an octahedral coordination center with trigonal distortion [CuO(6)](10-) have been calculated. The influence of possible types of oxygen octahedron distortions and possible displacement of copper ions from the symmetry center on the electron spectrum, as well as the shape of the adiabatic potential, has been analyzed. It is shown that in the low-temperature phase the multiple minima of the adiabatic potential occur due to tetragonal distortions while the depth of a minimum is determined by the degree of trigonal octahedron distortions. Tetragonal distortion values and multi-minimum potential barrier heights have been determined. PMID:21393785
Ionization potentials of large sodium doped ammonia clusters.
Steinbach, C; Buck, U
2005-04-01
In a continuous neat supersonic expansion ammonia clusters are generated and doped with sodium atoms in a pickup cell. Thus clusters of the form Na(NH(3))(n) are produced that are photoionized by a tunable dye laser system. The ions are mass analyzed in a reflectron time-of-flight mass spectrometer, and the wavelength dependent ion signals serve for the determination of the ionization potentials (IP) of the different clusters in the size range 10< or =n< or =1500. Aside from a plateau for 10< or =n< or =17 and smaller steps at n=24, 35, and 59 on the average a continuous decrease of the IP with cluster size is observed. The IPs in this size range are linear with (n+1)(-13) and extrapolate to IP(n=infinity)=1.66+/-0.01 eV. The slope is consistent with a dielectric continuum model of the solvated electron and the dielectric constant of the solid. The extrapolated IPs are compared with results obtained for negative ammonia cluster ions and metallic solutions in liquid ammonia. Differences are explained by the presence of counterions and their various distances from the solvated electron. PMID:15847459
Ionization potentials of large sodium doped ammonia clusters
NASA Astrophysics Data System (ADS)
Steinbach, C.; Buck, U.
2005-04-01
In a continuous neat supersonic expansion ammonia clusters are generated and doped with sodium atoms in a pickup cell. Thus clusters of the form Na(NH3)n are produced that are photoionized by a tunable dye laser system. The ions are mass analyzed in a reflectron time-of-flight mass spectrometer, and the wavelength dependent ion signals serve for the determination of the ionization potentials (IP) of the different clusters in the size range 10⩽n ⩽1500. Aside from a plateau for 10⩽n⩽17 and smaller steps at n =24, 35, and 59 on the average a continuous decrease of the IP with cluster size is observed. The IPs in this size range are linear with (n+1)-1/3 and extrapolate to IP (n=∞)=1.66±0.01eV. The slope is consistent with a dielectric continuum model of the solvated electron and the dielectric constant of the solid. The extrapolated IPs are compared with results obtained for negative ammonia cluster ions and metallic solutions in liquid ammonia. Differences are explained by the presence of counterions and their various distances from the solvated electron.
Krause, Pascal; Sonk, Jason A.; Schlegel, H. Bernhard
2014-05-07
Ionization rates of molecules have been modeled with time-dependent configuration interaction simulations using atom centered basis sets and a complex absorbing potential. The simulations agree with accurate grid-based calculations for the ionization of hydrogen atom as a function of field strength and for charge resonance enhanced ionization of H{sub 2}{sup +} as the bond is elongated. Unlike grid-based methods, the present approach can be applied to simulate electron dynamics and ionization in multi-electron polyatomic molecules. Calculations on HCl{sup +} and HCO{sup +} demonstrate that these systems also show charge resonance enhanced ionization as the bonds are stretched.
Accurate potential energy functions, non-adiabatic and spin-orbit couplings in the ZnH+ system
NASA Astrophysics Data System (ADS)
Liang, Guiying; Liu, Xiaoting; Zhang, Xiaomei; Xu, Haifeng; Yan, Bing
2016-03-01
A high-level ab initio calculation on the ZnH+ cation has been carried out with the multi-reference configuration interaction method plus Davison correction (MRCI + Q). The scalar relativistic effect is included by using the Douglas-Kroll-Hess (DKH) method. The calculated potential energy curves (PECs) of the 7 Λ-S states are associated with the dissociation limits of Zn+(2Sg) + H(2Sg), Zn(1Sg) + H+(1Sg), and Zn+(2Pu) + H(2Sg), respectively (The Λ-S state is labeled as 2S + 1Λ, in which Λ is the quantum number for the projection along the internuclear axis of the total electronic orbital angular momentum and S is the total electron spin). The spectroscopic constants of the bound states are determined and in good agreement with the available theoretical and experimental results. The permanent dipole moments (PDMs) of Λ-S states and the spin-orbit (SO) matrix elements between Λ-S states are also computed. The results show that the abrupt changes of the PDMs and SO matrix elements come into being for the reason of the avoided crossing between the states with the same symmetry. In addition, the non-adiabatic couplings matrix elements between Λ-S states are also evaluated. Finally, the spin-orbit couplings (SOCs) for the low-lying states are considered with Breit-Pauli operator. The SOC effect makes the 7 Λ-S states of the ZnH+ cation split into 12 Ω states (Ω = Λ + Sz, in which Sz is projection of the total electron spin S along the internuclear Z-axis). For the (3)0+ state, the two energy minima exhibit in the potential, which could be attributed to the formation of the new avoided crossing point. The transition dipole moments (TDMs), Franck-Condon factors, and the radiative lifetimes of the selected transitions (2)0+-X0+, (3)0+-X0+, (2)1-X0+ and (3)1-X0+ have been reported.
Accurate potential energy functions, non-adiabatic and spin-orbit couplings in the ZnH(+) system.
Liang, Guiying; Liu, Xiaoting; Zhang, Xiaomei; Xu, Haifeng; Yan, Bing
2016-03-01
A high-level ab initio calculation on the ZnH(+) cation has been carried out with the multi-reference configuration interaction method plus Davison correction (MRCI+Q). The scalar relativistic effect is included by using the Douglas-Kroll-Hess (DKH) method. The calculated potential energy curves (PECs) of the 7 Λ-S states are associated with the dissociation limits of Zn(+)((2)Sg)+H((2)Sg), Zn((1)Sg)+H(+)((1)Sg), and Zn(+)((2)Pu)+H((2)Sg), respectively (The Λ-S state is labeled as (2S+1)Λ, in which Λ is the quantum number for the projection along the internuclear axis of the total electronic orbital angular momentum and S is the total electron spin). The spectroscopic constants of the bound states are determined and in good agreement with the available theoretical and experimental results. The permanent dipole moments (PDMs) of Λ-S states and the spin-orbit (SO) matrix elements between Λ-S states are also computed. The results show that the abrupt changes of the PDMs and SO matrix elements come into being for the reason of the avoided crossing between the states with the same symmetry. In addition, the non-adiabatic couplings matrix elements between Λ-S states are also evaluated. Finally, the spin-orbit couplings (SOCs) for the low-lying states are considered with Breit-Pauli operator. The SOC effect makes the 7 Λ-S states of the ZnH(+) cation split into 12 Ω states (Ω=Λ+Sz, in which Sz is projection of the total electron spin S along the internuclear Z-axis). For the (3)0(+) state, the two energy minima exhibit in the potential, which could be attributed to the formation of the new avoided crossing point. The transition dipole moments (TDMs), Franck-Condon factors, and the radiative lifetimes of the selected transitions (2)0(+)-X0(+), (3)0(+)-X0(+), (2)1-X0(+) and (3)1-X0(+) have been reported. PMID:26637984
NASA Astrophysics Data System (ADS)
Athay, R. Grant
1994-03-01
Spectroscopic data from two flights of the Naval Research Laboratory's High Resolution Telescope and Spectrograph (HRTS) are analyzed for evidence of variations in relative abundances in the low chromosphere. Comparisons of sunspot, active region, and quiet-Sun data from HRTS II reveal decreases of intensities of sunspot lines from the first ionization stages of elements with low first ionization potential relative to both the active region and the quiet Sun. C I lines, however, are more intense in the sunspot than either the active region or the quiet Sun. Within a sunspot in Spacelab II data, the C I line at 156.1 nm is near its average intensity, whereas the Fe II line at 156.3 is much weaker than average. Both spots suggest a relative high value for the C I/Fe II abundance ratio. Within the zone of the same magnetic polarity as the sunspot (leading polarity) in the Spacelab II data, the brightest plages in C I show large C I/Fe II intensity ratios similar to those found in the sunspot. By contrast, the zones of following polarity on either side of the leading polarity show several well-defined areas of unusually low C I/Fe II intensity ratios associated with dark features in C I. The plages within these same zones have near normal or somewhat enhanced values for the C I/Fe II intensity ratios. It is noteworthy, also, that many of the brightest areas in C I do not coincide spatially with the brightest regions in Fe II. Neither do the darkest areas in C I align well with the darkest areas in Fe II. The association of high C I/Fe II intensity ratios with the zone of leading polarity and low-intensity ratios with zones of following polarity suggests that the iron abundance is dependent on the field polarity and is relatively low in the sunspot and the brighter plages in the zone of leading polarity and relatively high in C I dark flocculi in zones of following polarity. Failure of the brightest and darkest features in C I to align with the brightest and darkest
Measurement of the first ionization potential of lawrencium, element 103
NASA Astrophysics Data System (ADS)
Sato, T. K.; Asai, M.; Borschevsky, A.; Stora, T.; Sato, N.; Kaneya, Y.; Tsukada, K.; Düllmann, Ch. E.; Eberhardt, K.; Eliav, E.; Ichikawa, S.; Kaldor, U.; Kratz, J. V.; Miyashita, S.; Nagame, Y.; Ooe, K.; Osa, A.; Renisch, D.; Runke, J.; Schädel, M.; Thörle-Pospiech, P.; Toyoshima, A.; Trautmann, N.
2015-04-01
The chemical properties of an element are primarily governed by the configuration of electrons in the valence shell. Relativistic effects influence the electronic structure of heavy elements in the sixth row of the periodic table, and these effects increase dramatically in the seventh row--including the actinides--even affecting ground-state configurations. Atomic s and p1/2 orbitals are stabilized by relativistic effects, whereas p3/2, d and f orbitals are destabilized, so that ground-state configurations of heavy elements may differ from those of lighter elements in the same group. The first ionization potential (IP1) is a measure of the energy required to remove one valence electron from a neutral atom, and is an atomic property that reflects the outermost electronic configuration. Precise and accurate experimental determination of IP1 gives information on the binding energy of valence electrons, and also, therefore, on the degree of relativistic stabilization. However, such measurements are hampered by the difficulty in obtaining the heaviest elements on scales of more than one atom at a time. Here we report that the experimentally obtained IP1 of the heaviest actinide, lawrencium (Lr, atomic number 103), is electronvolts. The IP1 of Lr was measured with 256Lr (half-life 27 seconds) using an efficient surface ion-source and a radioisotope detection system coupled to a mass separator. The measured IP1 is in excellent agreement with the value of 4.963(15) electronvolts predicted here by state-of-the-art relativistic calculations. The present work provides a reliable benchmark for theoretical calculations and also opens the way for IP1 measurements of superheavy elements (that is, transactinides) on an atom-at-a-time scale.
Measurement of the first ionization potential of lawrencium, element 103.
Sato, T K; Asai, M; Borschevsky, A; Stora, T; Sato, N; Kaneya, Y; Tsukada, K; Düllmann, Ch E; Eberhardt, K; Eliav, E; Ichikawa, S; Kaldor, U; Kratz, J V; Miyashita, S; Nagame, Y; Ooe, K; Osa, A; Renisch, D; Runke, J; Schädel, M; Thörle-Pospiech, P; Toyoshima, A; Trautmann, N
2015-04-01
The chemical properties of an element are primarily governed by the configuration of electrons in the valence shell. Relativistic effects influence the electronic structure of heavy elements in the sixth row of the periodic table, and these effects increase dramatically in the seventh row--including the actinides--even affecting ground-state configurations. Atomic s and p1/2 orbitals are stabilized by relativistic effects, whereas p3/2, d and f orbitals are destabilized, so that ground-state configurations of heavy elements may differ from those of lighter elements in the same group. The first ionization potential (IP1) is a measure of the energy required to remove one valence electron from a neutral atom, and is an atomic property that reflects the outermost electronic configuration. Precise and accurate experimental determination of IP1 gives information on the binding energy of valence electrons, and also, therefore, on the degree of relativistic stabilization. However, such measurements are hampered by the difficulty in obtaining the heaviest elements on scales of more than one atom at a time. Here we report that the experimentally obtained IP1 of the heaviest actinide, lawrencium (Lr, atomic number 103), is 4.96(+0.08)(-0.07) electronvolts. The IP1 of Lr was measured with (256)Lr (half-life 27 seconds) using an efficient surface ion-source and a radioisotope detection system coupled to a mass separator. The measured IP1 is in excellent agreement with the value of 4.963(15) electronvolts predicted here by state-of-the-art relativistic calculations. The present work provides a reliable benchmark for theoretical calculations and also opens the way for IP1 measurements of superheavy elements (that is, transactinides) on an atom-at-a-time scale. PMID:25855457
Sevilla, M.D.; Colson, A.O. ); Besler, B. )
1995-01-19
Ab initio molecular orbital calculations of the electron affinities (EAs) and ionization potentials (IPs) of the DNA bases are presented in this work. Comparisons of calculated and experimental values are made for a series of compounds of size and/or structure similar to the DNA bases. Excellent correlations between calculated and experimental values are found for both Koopmans EAs at the 6-31G[sup *] and D95v levels and calculated vertical EAs of the model compounds. Several basis sets are considered: 6-31G[sup *], 6-31+G(d), and D95v. Calculations at 6-31G[sup *] and 6-31+G(d) using both ROHF and ROMP2 theories show a consistent difference between calculated vertical and adiabatic EAs. This allows for a good estimate of DNA base adiabatic EAs. i.e., -0.7, -0.3, 0.2, 0.3, and 0.4 eV; from the vertical EAs -1.23, -0.74, -0.40, -0.32, and -0.19 eV for G, A, C, T, and U respectively. While EAs must be scaled, we find that Koopmans IPs calculated at the simple 3-21G level predict vertical IPs of the DNA bases with only a 0.15 eV average absolute deviation from the experimentally reported values and calculations at MP2/6-31+G(d)//6-31G[sup *] for the adiabatic ionization potentials of the DNA bases are all within 0.1 eV of experiment. 41 refs., 2 figs., 5 tabs.
Song, Lingchun; Gao, Jiali
2009-01-01
A theoretical model is presented for deriving effective diabatic states based on ab initio self-consistent field valence bond (VBSCF) theory by reducing the multi-configurational VB Hamiltonian into an effective two-state model. We describe two computational approaches for the optimization of the effective diabatic configurations, resulting in two ways of interpreting such effective diabatic states. In the variational diabatic configuration (VDC) method, the energies of the individual diabatic states are variationally minimized. In the consistent diabatic configuration (CDC) method, both the configuration coefficients and orbital coefficients are simultaneously optimized to minimize the adiabatic ground-state energy in VBSCF calculations. In addition, we describe a mixed molecular orbital and valence bond (MOVB) approach to construct the CDC diabatic and adiabatic states for a chemical reaction, whereas the VDC-MOVB method has been described previously. Employing the symmetric SN2 reaction between NH3 and CH3NH3+ as a test system, we found that the results from ab initio VBSCF and from MOVB calculations are in good agreement, suggesting that the computationally efficient MOVB method is a reasonable model for VB simulations of condensed phase reactions. The results indicate that CDC and VDC diabatic states converge, respectively, to covalent and ionic states as the molecular geometries are distorted from the minimum of the respective diabatic state along the reaction coordinate. Furthermore, the resonance energy that stabilizes the energy of crossing between the two diabatic states, resulting in the transition state of the adiabatic ground-state reaction, has a strong dependence on the overlap integral between the two diabatic states and is a function of both the exchange integral and the total diabatic ground-state energy. PMID:18828577
NASA Astrophysics Data System (ADS)
Saheer, V. C.; Kumar, Sanjay
2016-01-01
The global ground and first three excited electronic state adiabatic as well as the corresponding quasidiabatic potential energy surfaces is reported as a function of nuclear geometries in the Jacobi coordinates ( R → , r → , γ ) using Dunning's cc-pVTZ basis set at the internally contracted multi-reference (single and double) configuration interaction level of accuracy. Nonadiabatic couplings, arising out of relative motion of proton and the vibrational motion of CO, are also reported in terms of coupling potentials. The quasidiabatic potential energy surfaces and the coupling potentials have been obtained using the ab initio procedure [Simah et al., J. Chem. Phys. 111, 4523 (1999)] for the purpose of dynamics studies.
The ionization potentials of atomic ions in laser-irradiated Ar, Kr and Xe clusters
NASA Astrophysics Data System (ADS)
Gets, A. V.; Krainov, V. P.
2006-04-01
The ionization potentials of atomic ions in laser-irradiated Ar, Kr and Xe clusters are derived as functions of electron temperature. These potentials decrease significantly compared to the case of the isolated atomic ions because of the screening effect by the atomic ions and electrons inside the cluster. The results can be used for derivations of inner ionization by impact collisions of hot electrons with atomic ions and by the static Coulomb field of the ionized cluster. The broadening of atomic states by the quasistatic Holtsmark field of atomic ions is also considered.
Shoulder, J M; Alderman, N S; Breneman, C M; Nyman, M C
2013-08-01
Property-Encoded Surface Translator (PEST) descriptors were found to be correlated with the degradation rates of polycyclic aromatic hydrocarbons (PAHs) by the peroxy-acid process. Reaction rate constants (k) in hr(-1) for nine PAHs (acenaphthene, anthracene, benzo[a]pyrene, benzo[k]fluoranthene, fluoranthene, fluorene, naphthalene, phenanthrene, and pyrene) were determined by a peroxy-acid treatment method that utilized acetic acid, hydrogen peroxide, and a sulphuric acid catalyst to degrade the polyaromatic structures. Molecular properties of the selected nine PAHs were derived from structures optimized at B3LYP/6-31G(d) and HF/6-31G(d) levels of theory. Properties of adiabatic and vertical ionization potential (IP), highest occupied molecular orbitals (HOMO), HOMO/lowest unoccupied molecular orbital (LUMO) gap energies and HOMO/singly occupied molecular orbital (SOMO) gap energies were not correlated with rates of peroxy-acid reaction. PEST descriptors were calculated from B3LYP/6-31G(d) optimized structures and found to have significant levels of correlation with k. PIP Min described the minimum local IP on the surface of the molecule and was found to be related to k. PEST technology appears to be an accurate method in predicting reactivity and could prove to be a valuable asset in building treatment models and in remediation design for PAHs and other organic contaminants in the environment. PMID:23734862
Two-color multiphoton ionization of diazabicyclooctane in a supersonic free jet
NASA Astrophysics Data System (ADS)
Fujii, Masaaki; Ebata, Takayuki; Mikami, Naohiko; Ito, Mitsuo
1983-11-01
Two-color multiphoton ionization (MPI) spectroscopy has been applied for diazabicyclooctane (DABCO) in a supersonic free jet. The MPI spectra due to transitions from the various vibronic levels of the S 1 (3s Rydberg) state which were excited by the first laser revealed the high Rydberg states above the adiabatic ionization potential. The ionization process and the vibrational potential of the ion are discussed.
Ionization potentials of cobalt and nickel ions in the local-spin-density approximation
Dhar, S. ); Kestner, N.R. )
1990-06-15
In this article we report on the ionization potentials of all configurations of the Co{sup {ital n}+} and Ni{sup {ital n}+} ions obtained via transition-state calculations using local-spin-density (LSD) potentials. The calculations were performed numerically with and without modifications of the local exchange potential for fractional occupation numbers. When the exchange potential is corrected for noninteger occupation numbers, a more consistent picture of the ionization process is obtained than that given by the LSD Kohn-Sham exchange. The agreement with experimental results is also significantly improved.
Ionization Potential Depression in Hot Dense Plasmas Through a Pure Classical Model
NASA Astrophysics Data System (ADS)
Calisti, A.; Ferri, S.; Talin, B.
2015-05-01
The ionization potential of an ion embedded in a plasma, lowered due to the whole of the charged particles (ions and electrons) interacting with this ion, is the so-called plasma effect. A numerical plasma model based on classical molecular dynamics has been developed recently. It is capable to describe a neutral plasma at equilibrium involving ions of various charge states of the same atom together with electrons. This code is used here to investigate the ionization potential depression (IPD). The study of the IPD is illustrated and discussed for aluminum plasmas at mid and solid density and electron temperatures varying from 50eV to 190eV. The method relies on a sampling of the total potential energy of the electron located at an ion being ionized. The potential energy of such electron results from all of the interacting charged particles interacting with it.
Radioprotective Potential of Plants and Herbs against the Effects of Ionizing Radiation
C. Jagetia, Ganesh
2007-01-01
Ionizing radiations produce deleterious effects in the living organisms and the rapid technological advancement has increased human exposure to ionizing radiations enormously. There is a need to protect humans against such effects of ionizing radiation. Attempts to protect against the deleterious effects of ionizing radiations by pharmacological intervention were made as early as 1949 and efforts are continued to search radioprotectors, which may be of great help for human application. This review mainly dwells on the radioprotective potential of plant and herbal extracts. The results obtained from in vitro and in vivo studies indicate that several botanicals such as Gingko biloba, Centella asiatica, Hippophae rhamnoides, Ocimum sanctum, Panax ginseng, Podophyllum hexandrum, Amaranthus paniculatus, Emblica officinalis, Phyllanthus amarus, Piper longum, Tinospora cordifoila, Mentha arvensis, Mentha piperita, Syzygium cumini, Zingiber officinale, Ageratum conyzoides, Aegle marmelos and Aphanamixis polystachya protect against radiation-induced lethality, lipid peroxidation and DNA damage. The fractionation-guided evaluation may help to develop new radioprotectors of desired activities. PMID:18188408
Laser-induced resonance states as dynamic suppressors of ionization in high-frequency short pulses
Barash, Danny; Orel, Ann E.; Baer, Roi
2000-01-01
An adiabatic-Floquet formalism is used to study the suppression of ionization in short laser pulses. In the high-frequency limit the adiabatic equations involve only the pulse envelope where transitions are purely ramp effects. For a short-ranged potential having a single-bound state we show that ionization suppression is caused by the appearance of a laser-induced resonance state, which is coupled by the pulse ramp to the ground state and acts to trap ionizing flux. (c) 1999 The American Physical Society.
NASA Astrophysics Data System (ADS)
Cremers, C.; Degen, J.
1998-11-01
Coexistence of Jahn-Teller minima resulting from the coupling to different accepting modes within the adiabatic potential energy surface (APES) is not possible within the framework of linear vibronic coupling theory. For the lowest exited triplet state 3T1u of inorganic complexes with s2 electronic ground-state configuration, such a coexistence, due to quadratic coupling effects, is discussed. As a direct experimental evidence two vibronic progressions with different accepting modes in the emission spectra resulting from a single electronic state are observed in the emission spectra of the title compounds. The observation of vibronic finestructure in the emission spectra of [TeCl6]2- is reported for the first time.
Exact Potential Driving the Electron Dynamics in Enhanced Ionization of H2+
NASA Astrophysics Data System (ADS)
Khosravi, Elham; Abedi, Ali; Maitra, Neepa T.
2015-12-01
It was recently shown that the exact factorization of the electron-nuclear wave function allows the construction of a Schrödinger equation for the electronic system, in which the potential contains exactly the effect of coupling to the nuclear degrees of freedom and any external fields. Here we study the exact potential acting on the electron in charge-resonance enhanced ionization in a model one-dimensional H2+ molecule. We show there can be significant differences between the exact potential and that used in the traditional quasistatic analyses, arising from nonadiabatic coupling to the nuclear system, and that these are crucial to include for accurate simulations of time-resolved ionization dynamics and predictions of the ionization yield.
Density-functional errors in ionization potential with increasing system size
NASA Astrophysics Data System (ADS)
Whittleton, Sarah R.; Sosa Vazquez, Xochitl A.; Isborn, Christine M.; Johnson, Erin R.
2015-05-01
This work investigates the effects of molecular size on the accuracy of density-functional ionization potentials for a set of 28 hydrocarbons, including series of alkanes, alkenes, and oligoacenes. As the system size increases, delocalization error introduces a systematic underestimation of the ionization potential, which is rationalized by considering the fractional-charge behavior of the electronic energies. The computation of the ionization potential with many density-functional approximations is not size-extensive due to excessive delocalization of the incipient positive charge. While inclusion of exact exchange reduces the observed errors, system-specific tuning of long-range corrected functionals does not generally improve accuracy. These results emphasize that good performance of a functional for small molecules is not necessarily transferable to larger systems.
Density-functional errors in ionization potential with increasing system size
Whittleton, Sarah R.; Sosa Vazquez, Xochitl A.; Isborn, Christine M.; Johnson, Erin R.
2015-05-14
This work investigates the effects of molecular size on the accuracy of density-functional ionization potentials for a set of 28 hydrocarbons, including series of alkanes, alkenes, and oligoacenes. As the system size increases, delocalization error introduces a systematic underestimation of the ionization potential, which is rationalized by considering the fractional-charge behavior of the electronic energies. The computation of the ionization potential with many density-functional approximations is not size-extensive due to excessive delocalization of the incipient positive charge. While inclusion of exact exchange reduces the observed errors, system-specific tuning of long-range corrected functionals does not generally improve accuracy. These results emphasize that good performance of a functional for small molecules is not necessarily transferable to larger systems.
Schramm, E; Mühlberger, F; Mitschke, S; Reichardt, G; Schulte-Ladbeck, R; Pütz, M; Zimmermann, R
2008-02-01
Several ionization potentials (IPs) of security relevant substances were determined with single photon ionization time of flight mass spectrometry (SPI-TOFMS) using monochromatized synchrotron radiation from the "Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung" (BESSY). In detail, the IPs of nine explosives and related compounds, seven narcotics and narcotics precursors, and one chemical warfare agent (CWA) precursor were determined, whereas six IPs already known from the literature were verified correctly. From seven other substances, including one CWA precursor, the IP could not be determined as the molecule ion peak could not be detected. For these substances the appearance energy (AE) of a main fragment was determined. The analyzed security-relevant substances showed IPs significantly below the IPs of common matrix compounds such as nitrogen and oxygen. Therefore, it is possible to find photon energies in between, whereby the molecules of interest can be detected with SPI in very low concentrations due to the shielding of the matrix. All determined IPs except the one of the explosive EGDN were below 10.5 eV. Hence, laser-generated 118 nm photons can be applied for detecting almost all security-relevant substances by, e.g., SPI-TOFMS. PMID:18284801
NASA Astrophysics Data System (ADS)
Doyle, J. G.; Giunta, A.; Singh, A.; Madjarska, M. S.; Summers, H.; Kellett, B. J.; O'Mullane, M.
2012-09-01
We discuss the diagnostic potential of high cadence UV spectral data when transient ionization is considered. For this we use high cadence UV spectra taken during the impulsive phase of a solar flare (observed with instruments on-board the Solar Maximum Mission) which showed excellent correspondence with hard X-ray pulses. The ionization fraction of the transition region ion O v and, in particular, the contribution function for the O v 1371 Å line are computed within the Atomic Data and Analysis Structure, which is a collection of fundamental and derived atomic data and codes to manipulate them. Due to transient ionization, the O v 1371 Å line is enhanced in the first fraction of a second with the peak in the line contribution function occurring initially at a higher electron temperature than in ionization equilibrium. The rise time and enhancement factor depend mostly on the electron density. The fractional increase in the O v 1371 Å emissivity due to transient ionization can reach a factor of two-four and can explain the fast response in the line flux of transition regions ions during the impulsive phase of flares solely as a result of transient ionization. This technique can be used to diagnose the electron temperature and density of solar flares observed with the forthcoming Interface Region Imaging Spectrograph.
NASA Astrophysics Data System (ADS)
Johnson, E.; Fricke, B.; Jacob, T.; Dong, C. Z.; Fritzsche, S.; Pershina, V.
2002-02-01
Large multiconfiguration Dirac-Fock calculations were performed for all neutral and up to 7 and 8 times ionized species of elements 107 and 108, respectively, as well as all the homologous elements Mn, Tc, Re, Fe, Ru, and Os for a number of different total angular momenta. Comparison of the resulting ionization potentials to the known values of the homologues allow an extrapolation and thus a prediction of the chemically important seven or eight ionization potentials of elements 107 or 108 as well as a prediction of some ionic radii.
NASA Technical Reports Server (NTRS)
Goodrich, C. C.; Scudder, J. D.
1984-01-01
The adiabatic energy gain of electrons in the stationary electric and magnetic field structure of collisionless shock waves was examined analytically in reference to conditions of the earth's bow shock. The study was performed to characterize the behavior of electrons interacting with the cross-shock potential. A normal incidence frame (NIF) was adopted in order to calculate the reversible energy change across a time stationary shock, and comparisons were made with predictions made by the de Hoffman-Teller (HT) model (1950). The electron energy gain, about 20-50 eV, is demonstrated to be consistent with a 200-500 eV potential jump in the bow shock quasi-perpendicular geometry. The electrons lose energy working against the solar wind motional electric field. The reversible energy process is close to that modeled by HT, which predicts that the motional electric field vanishes and the electron energy gain from the electric potential is equated to the ion energy loss to the potential.
Ultrafast ionization and fragmentation of molecular silane
Sayres, Scott G.; Ross, Matt W.; Castleman, A. W. Jr.
2010-09-15
The ionization and fragmentation of molecular silane is examined here with laser intensities ranging between 7x10{sup 12} and 1x10{sup 15} W/cm{sup 2} at 624 nm. The ionization potential of silane determined using both multiphoton ionization (MPI) and tunneling ionization (TI) models agrees with the vertical ionization potential of the molecule. In addition, the application of the tunneling ionization model is extended here to the fragments of silane to determine their appearance potentials. MPI values for SiH{sub 3}{sup +}, SiH{sub 2}{sup +}, SiH{sup +}, Si{sup +}, as well as H{sub 2}{sup +} and H{sup +} are consistent with vertical potentials, whereas the TI measurements are found to be in accord with adiabatic potentials. The tunneling appearance potentials observed for the fragments H{sub 2}{sup +} and H{sup +} are lower than reported for other techniques. In fact, the appearance potential measurements for these species resulting from silane are lower than their ionization potentials. The fragmentation rate of silane is determined to be nearly 20 times larger than the ionization rate. The main precursor for producing amorphous silicon (a-Si:H) thin films, SiH{sub 3}{sup +} is the dominant fragmentation product making up roughly a third of the total ion yield, a substantial increase from other techniques.
Size-dependent error of the density functional theory ionization potential in vacuum and solution
Sosa Vazquez, Xochitl A.; Isborn, Christine M.
2015-12-28
Density functional theory is often the method of choice for modeling the energetics of large molecules and including explicit solvation effects. It is preferable to use a method that treats systems of different sizes and with different amounts of explicit solvent on equal footing. However, recent work suggests that approximate density functional theory has a size-dependent error in the computation of the ionization potential. We here investigate the lack of size-intensivity of the ionization potential computed with approximate density functionals in vacuum and solution. We show that local and semi-local approximations to exchange do not yield a constant ionization potential for an increasing number of identical isolated molecules in vacuum. Instead, as the number of molecules increases, the total energy required to ionize the system decreases. Rather surprisingly, we find that this is still the case in solution, whether using a polarizable continuum model or with explicit solvent that breaks the degeneracy of each solute, and we find that explicit solvent in the calculation can exacerbate the size-dependent delocalization error. We demonstrate that increasing the amount of exact exchange changes the character of the polarization of the solvent molecules; for small amounts of exact exchange the solvent molecules contribute a fraction of their electron density to the ionized electron, but for larger amounts of exact exchange they properly polarize in response to the cationic solute. In vacuum and explicit solvent, the ionization potential can be made size-intensive by optimally tuning a long-range corrected hybrid functional.
Size-dependent error of the density functional theory ionization potential in vacuum and solution
Sosa Vazquez, Xochitl A.; Isborn, Christine M.
2015-12-22
Density functional theory is often the method of choice for modeling the energetics of large molecules and including explicit solvation effects. It is preferable to use a method that treats systems of different sizes and with different amounts of explicit solvent on equal footing. However, recent work suggests that approximate density functional theory has a size-dependent error in the computation of the ionization potential. We here investigate the lack of size-intensivity of the ionization potential computed with approximate density functionals in vacuum and solution. We show that local and semi-local approximations to exchange do not yield a constant ionization potential for an increasing number of identical isolated molecules in vacuum. Instead, as the number of molecules increases, the total energy required to ionize the system decreases. Rather surprisingly, we find that this is still the case in solution, whether using a polarizable continuum model or with explicit solvent that breaks the degeneracy of each solute, and we find that explicit solvent in the calculation can exacerbate the size-dependent delocalization error. We demonstrate that increasing the amount of exact exchange changes the character of the polarization of the solvent molecules; for small amounts of exact exchange the solvent molecules contribute a fraction of their electron density to the ionized electron, but for larger amounts of exact exchange they properly polarize in response to the cationic solute. As a result, in vacuum and explicit solvent, the ionization potential can be made size-intensive by optimally tuning a long-range corrected hybrid functional.
Andreev, S.V.; Mishin, V.I.; Letokhov, V.S.
1988-10-01
A highly sensitive method of detecting atoms in samples has been used for spectral investigations of the rare radioactive element Fr. The method is based on laser-resonance photoionization of Fr atoms in a hot quasi-enclosed cavity. The investigations have been carried out with samples in which short-lived radioactive /sup 221/Fr atoms formed at a rate of approximately 10/sup 3/ atoms/sec. The data obtained, to our knowledge for the first time, on the energies of the high-lying Rydberg levels of the /sup 2/S/sub 1/2/ and /sup 2/D series have made it possible to determine the electron binding energy of the 7p /sup 2/P/sub 3/2/ state and to establish the ionization potential of Fr accurately.
NASA Technical Reports Server (NTRS)
Huo, Winifred M.; Kim, Yong-Ki
1999-01-01
Based on the Binary-Encounter-Bethe (BEB) model, the advantage of using relativistic effective core potentials (RECP) in the calculation of total ionization cross sections of heavy atoms or molecules containing heavy atoms is discussed. Numerical examples for Ar, Kr, Xe, and WF6 are presented.
Size-dependent error of the density functional theory ionization potential in vacuum and solution
Sosa Vazquez, Xochitl A.; Isborn, Christine M.
2015-12-22
Density functional theory is often the method of choice for modeling the energetics of large molecules and including explicit solvation effects. It is preferable to use a method that treats systems of different sizes and with different amounts of explicit solvent on equal footing. However, recent work suggests that approximate density functional theory has a size-dependent error in the computation of the ionization potential. We here investigate the lack of size-intensivity of the ionization potential computed with approximate density functionals in vacuum and solution. We show that local and semi-local approximations to exchange do not yield a constant ionization potentialmore » for an increasing number of identical isolated molecules in vacuum. Instead, as the number of molecules increases, the total energy required to ionize the system decreases. Rather surprisingly, we find that this is still the case in solution, whether using a polarizable continuum model or with explicit solvent that breaks the degeneracy of each solute, and we find that explicit solvent in the calculation can exacerbate the size-dependent delocalization error. We demonstrate that increasing the amount of exact exchange changes the character of the polarization of the solvent molecules; for small amounts of exact exchange the solvent molecules contribute a fraction of their electron density to the ionized electron, but for larger amounts of exact exchange they properly polarize in response to the cationic solute. As a result, in vacuum and explicit solvent, the ionization potential can be made size-intensive by optimally tuning a long-range corrected hybrid functional.« less
HF echoes from ionization potentially produced by high-altitude discharges
Roussel-Dupre, R.; Fitzgerald, T.J.; Symbalisty, E.
1997-04-01
In this paper the authors report on recent radar measurements taken during the month of October 1994 with the LDG HF radar in the Ivory Coast, Africa as part of the International Equatorial Electrojet Year. The purpose of this experimental effort in part was to study the effects of thunderstorms on the ionosphere. At the same time, the authors decided to carry out a set of experiments of an exploratory nature to look for echoes that could potentially arise from ionization produced in the mesosphere. The two leading candidates for producing transient ionization in the mesosphere are meteors and high-altitude discharges. Each is discussed in the context of these measurements.
NASA Astrophysics Data System (ADS)
Chuluunbaatar, O.; Gusev, A. A.; Gerdt, V. P.; Rostovtsev, V. A.; Vinitsky, S. I.; Abrashkevich, A. G.; Kaschiev, M. S.; Serov, V. V.
2008-02-01
A FORTRAN 77 program is presented which calculates with the relative machine precision potential curves and matrix elements of the coupled adiabatic radial equations for a hydrogen-like atom in a homogeneous magnetic field. The potential curves are eigenvalues corresponding to the angular oblate spheroidal functions that compose adiabatic basis which depends on the radial variable as a parameter. The matrix elements of radial coupling are integrals in angular variables of the following two types: product of angular functions and the first derivative of angular functions in parameter, and product of the first derivatives of angular functions in parameter, respectively. The program calculates also the angular part of the dipole transition matrix elements (in the length form) expressed as integrals in angular variables involving product of a dipole operator and angular functions. Moreover, the program calculates asymptotic regular and irregular matrix solutions of the coupled adiabatic radial equations at the end of interval in radial variable needed for solving a multi-channel scattering problem by the generalized R-matrix method. Potential curves and radial matrix elements computed by the POTHMF program can be used for solving the bound state and multi-channel scattering problems. As a test desk, the program is applied to the calculation of the energy values, a short-range reaction matrix and corresponding wave functions with the help of the KANTBP program. Benchmark calculations for the known photoionization cross-sections are presented. Program summaryProgram title:POTHMF Catalogue identifier:AEAA_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAA_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.:8123 No. of bytes in distributed program, including test data
Song, Xiaohong; Lin, Cheng; Sheng, Zhihao; Liu, Peng; Chen, Zhangjin; Yang, Weifeng; Hu, Shilin; Lin, C D; Chen, Jing
2016-01-01
Strong field photoelectron holography has been proposed as a means for interrogating the spatial and temporal information of electrons and ions in a dynamic system. After ionization, part of the electron wave packet may directly go to the detector (the reference wave), while another part may be driven back and scatters off the ion(the signal wave). The interference hologram of the two waves may be used to extract target information embedded in the collision process. Unlike conventional optical holography, however, propagation of the electron wave packet is affected by the Coulomb potential as well as by the laser field. In addition, electrons are emitted over the whole laser pulse duration, thus multiple interferences may occur. In this work, we used a generalized quantum-trajectory Monte Carlo method to investigate the effect of Coulomb potential and the nonadiabatic subcycle ionization on the photoelectron hologram. We showed that photoelectron hologram can be well described only when the effect of nonadiabatic ionization is accounted for, and Coulomb potential can be neglected only in the tunnel ionization regime. Our results help paving the way for establishing photoelectron holography for probing spatial and dynamic properties of atoms and molecules. PMID:27329071
Song, Xiaohong; Lin, Cheng; Sheng, Zhihao; Liu, Peng; Chen, Zhangjin; Yang, Weifeng; Hu, Shilin; Lin, C. D.; Chen, Jing
2016-01-01
Strong field photoelectron holography has been proposed as a means for interrogating the spatial and temporal information of electrons and ions in a dynamic system. After ionization, part of the electron wave packet may directly go to the detector (the reference wave), while another part may be driven back and scatters off the ion(the signal wave). The interference hologram of the two waves may be used to extract target information embedded in the collision process. Unlike conventional optical holography, however, propagation of the electron wave packet is affected by the Coulomb potential as well as by the laser field. In addition, electrons are emitted over the whole laser pulse duration, thus multiple interferences may occur. In this work, we used a generalized quantum-trajectory Monte Carlo method to investigate the effect of Coulomb potential and the nonadiabatic subcycle ionization on the photoelectron hologram. We showed that photoelectron hologram can be well described only when the effect of nonadiabatic ionization is accounted for, and Coulomb potential can be neglected only in the tunnel ionization regime. Our results help paving the way for establishing photoelectron holography for probing spatial and dynamic properties of atoms and molecules. PMID:27329071
NASA Astrophysics Data System (ADS)
Song, Xiaohong; Lin, Cheng; Sheng, Zhihao; Liu, Peng; Chen, Zhangjin; Yang, Weifeng; Hu, Shilin; Lin, C. D.; Chen, Jing
2016-06-01
Strong field photoelectron holography has been proposed as a means for interrogating the spatial and temporal information of electrons and ions in a dynamic system. After ionization, part of the electron wave packet may directly go to the detector (the reference wave), while another part may be driven back and scatters off the ion(the signal wave). The interference hologram of the two waves may be used to extract target information embedded in the collision process. Unlike conventional optical holography, however, propagation of the electron wave packet is affected by the Coulomb potential as well as by the laser field. In addition, electrons are emitted over the whole laser pulse duration, thus multiple interferences may occur. In this work, we used a generalized quantum-trajectory Monte Carlo method to investigate the effect of Coulomb potential and the nonadiabatic subcycle ionization on the photoelectron hologram. We showed that photoelectron hologram can be well described only when the effect of nonadiabatic ionization is accounted for, and Coulomb potential can be neglected only in the tunnel ionization regime. Our results help paving the way for establishing photoelectron holography for probing spatial and dynamic properties of atoms and molecules.
Song, Xiaohong; Lin, Cheng; Sheng, Zhihao; Liu, Peng; Chen, Zhangjin; Yang, Weifeng; Hu, Shilin; Lin, C. D.; Chen, Jing
2016-06-22
Strong field photoelectron holography has been proposed as a means for interrogating the spatial and temporal information of electrons and ions in a dynamic system. After ionization, part of the electron wave packet may directly go to the detector (the reference wave), while another part may be driven back and scatters off the ion(the signal wave). The interference hologram of the two waves may be used to extract target information embedded in the collision process. Unlike conventional optical holography, however, propagation of the electron wave packet is affected by the Coulomb potential as well as by the laser field. Inmore » addition, electrons are emitted over the whole laser pulse duration, thus multiple interferences may occur. In this work, we used a generalized quantum-trajectory Monte Carlo method to investigate the effect of Coulomb potential and the nonadiabatic subcycle ionization on the photoelectron hologram. Here, we showed that photoelectron hologram can be well described only when the effect of nonadiabatic ionization is accounted for, and Coulomb potential can be neglected only in the tunnel ionization regime. Our results help paving the way for establishing photoelectron holography for probing spatial and dynamic properties of atoms and molecules.« less
NASA Astrophysics Data System (ADS)
Yonehara, Takehiro; Takatsuka, Kazuo
2012-12-01
We develop a theory and the method of its application for chemical dynamics in systems, in which the adiabatic potential energy hyper-surfaces (PES) are densely quasi-degenerate to each other in a wide range of molecular geometry. Such adiabatic electronic states tend to couple each other through strong nonadiabatic interactions. Technically, therefore, it is often extremely hard to accurately single out the individual PES in those systems. Moreover, due to the mutual nonadiabatic couplings that may spread wide in space and due to the energy-time uncertainty relation, the notion of the isolated and well-defined potential energy surface should lose the sense. On the other hand, such dense electronic states should offer a very interesting molecular field in which chemical reactions to proceed in characteristic manners. However, to treat these systems, the standard theoretical framework of chemical reaction dynamics, which starts from the Born-Oppenheimer approximation and ends up with quantum nuclear wavepacket dynamics, is not very useful. We here explore this problem with our developed nonadiabatic electron wavepacket theory, which we call the phase-space averaging and natural branching (PSANB) method [T. Yonehara and K. Takatsuka, J. Chem. Phys. 129, 134109 (2008)], 10.1063/1.2987302, or branching-path representation, in which the packets are propagated in time along the non-Born-Oppenheimer branching paths. In this paper, after outlining the basic theory, we examine using a one-dimensional model how well the PSANB method works with such densely quasi-degenerate nonadiabatic systems. To do so, we compare the performance of PSANB with the full quantum mechanical results and those given by the fewest switches surface hopping (FSSH) method, which is known to be one of the most reliable and flexible methods to date. It turns out that the PSANB electron wavepacket approach actually yields very good results with far fewer initial sampling paths. Then we apply the
Adiabatic potential-energy curves of long-range Rydberg molecules: Two-electron R -matrix approach
NASA Astrophysics Data System (ADS)
Tarana, Michal; Čurík, Roman
2016-01-01
We introduce a computational method developed for study of long-range molecular Rydberg states of such systems that can be approximated by two electrons in a model potential of the atomic cores. Only diatomic molecules are considered. The method is based on a two-electron R -matrix approach inside a sphere centered on one of the atoms. The wave function is then connected to a Coulomb region outside the sphere via a multichannel version of the Coulomb Green's function. This approach is put into a test by its application to a study of Rydberg states of the hydrogen molecule for internuclear distances R from 20 to 400 bohrs and energies corresponding to n from 3 to 22. The results are compared with previous quantum chemical calculations (lower quantum numbers n ) and computations based on contact-potential models (higher quantum numbers n ).
NASA Astrophysics Data System (ADS)
Gelb, Lev D.; Chakraborty, Somendra Nath
2011-12-01
The normal boiling points are obtained for a series of metals as described by the "quantum-corrected Sutton Chen" (qSC) potentials [S.-N. Luo, T. J. Ahrens, T. Çağın, A. Strachan, W. A. Goddard III, and D. C. Swift, Phys. Rev. B 68, 134206 (2003)]. Instead of conventional Monte Carlo simulations in an isothermal or expanded ensemble, simulations were done in the constant-NPH adabatic variant of the Gibbs ensemble technique as proposed by Kristóf and Liszi [Chem. Phys. Lett. 261, 620 (1996)]. This simulation technique is shown to be a precise tool for direct calculation of boiling temperatures in high-boiling fluids, with results that are almost completely insensitive to system size or other arbitrary parameters as long as the potential truncation is handled correctly. Results obtained were validated using conventional NVT-Gibbs ensemble Monte Carlo simulations. The qSC predictions for boiling temperatures are found to be reasonably accurate, but substantially underestimate the enthalpies of vaporization in all cases. This appears to be largely due to the systematic overestimation of dimer binding energies by this family of potentials, which leads to an unsatisfactory description of the vapor phase.
Gelb, Lev D; Chakraborty, Somendra Nath
2011-12-14
The normal boiling points are obtained for a series of metals as described by the "quantum-corrected Sutton Chen" (qSC) potentials [S.-N. Luo, T. J. Ahrens, T. Çağın, A. Strachan, W. A. Goddard III, and D. C. Swift, Phys. Rev. B 68, 134206 (2003)]. Instead of conventional Monte Carlo simulations in an isothermal or expanded ensemble, simulations were done in the constant-NPH adabatic variant of the Gibbs ensemble technique as proposed by Kristóf and Liszi [Chem. Phys. Lett. 261, 620 (1996)]. This simulation technique is shown to be a precise tool for direct calculation of boiling temperatures in high-boiling fluids, with results that are almost completely insensitive to system size or other arbitrary parameters as long as the potential truncation is handled correctly. Results obtained were validated using conventional NVT-Gibbs ensemble Monte Carlo simulations. The qSC predictions for boiling temperatures are found to be reasonably accurate, but substantially underestimate the enthalpies of vaporization in all cases. This appears to be largely due to the systematic overestimation of dimer binding energies by this family of potentials, which leads to an unsatisfactory description of the vapor phase. PMID:22168686
NASA Astrophysics Data System (ADS)
Bø, Iselin M. Th.; Esser, Ruth; Lie-Svendsen, Øystein
2013-05-01
We model the effect of gravitational settling in the upper chromosphere on O, Fe, Si, and Ne, studying whether Coulomb collisions between ionized low First Ionization Potential (FIP) elements and protons is sufficient to cause abundance enhancements relative to oxygen. We find that low-FIP abundance enhancements comparable to observed values can be obtained provided the hydrogen ionization degree lies in the approximate range 10%-30%, which agrees with chromospheric models. Lower or higher hydrogen ionization causes the FIP-effect to become smaller or absent (depletion of all heavy elements). Iron must be almost fully ionized in order to become enriched relative to high-FIP elements, and this requires a high iron photoionization rate. The time scale necessary to produce the enrichment increases rapidly with increasing H ionization. For iron in a background from a semiempirical chromospheric model, with an H ion fraction of the order of 30%-40% in the upper chromosphere, 1-2 hr of settling is required to produce enhancements comparable to observations. The absolute abundance (relative to H), which monotonically decreases with time during settling, has by that time decreased by less than 50% in the same altitude region. With the same background conditions, the silicon abundance is more strongly enhanced by the settling than the iron abundance. The high-FIP element neon is depleted, relative to O and low-FIP elements, in the same background and altitude region where iron is enhanced, typically by 50% or more relative to O after 1-2 hr of settling.
Bo, Iselin M. Th.; Esser, Ruth; Lie-Svendsen, Oystein E-mail: ruth.esser@uit.no
2013-05-20
We model the effect of gravitational settling in the upper chromosphere on O, Fe, Si, and Ne, studying whether Coulomb collisions between ionized low First Ionization Potential (FIP) elements and protons is sufficient to cause abundance enhancements relative to oxygen. We find that low-FIP abundance enhancements comparable to observed values can be obtained provided the hydrogen ionization degree lies in the approximate range 10%-30%, which agrees with chromospheric models. Lower or higher hydrogen ionization causes the FIP-effect to become smaller or absent (depletion of all heavy elements). Iron must be almost fully ionized in order to become enriched relative to high-FIP elements, and this requires a high iron photoionization rate. The time scale necessary to produce the enrichment increases rapidly with increasing H ionization. For iron in a background from a semiempirical chromospheric model, with an H ion fraction of the order of 30%-40% in the upper chromosphere, 1-2 hr of settling is required to produce enhancements comparable to observations. The absolute abundance (relative to H), which monotonically decreases with time during settling, has by that time decreased by less than 50% in the same altitude region. With the same background conditions, the silicon abundance is more strongly enhanced by the settling than the iron abundance. The high-FIP element neon is depleted, relative to O and low-FIP elements, in the same background and altitude region where iron is enhanced, typically by 50% or more relative to O after 1-2 hr of settling.
Borovkov, V I; Beregovaya, I V; Shchegoleva, L N; Potashov, P A; Bagryansky, V A; Molin, Y N
2012-09-14
Paramagnetic spin-lattice relaxation (SLR) in radical cations (RCs) of the cycloalkane series in liquid solution was studied and analyzed from the point of view of the correlation between the relaxation rate and the structure of the adiabatic potential energy surface (PES) of the RCs. SLR rates in the RCs formed in x-ray irradiated n-hexane solutions of the cycloalkanes studied were measured with the method of time-resolved magnetic field effect in the recombination fluorescence of spin-correlated radical ion pairs. Temperature and, for some cycloalkanes, magnetic field dependences of the relaxation rate were determined. It was found that the conventional Redfield theory of the paramagnetic relaxation as applied to the results on cyclohexane RC, gave a value of about 0.2 ps for the correlation time of the perturbation together with an unrealistically high value of 0.1 T in field units for the matrix element of the relaxation transition. The PES structure was obtained with the DFT quantum-chemical calculations. It was found that for all of the cycloalkanes RCs considered, including low symmetric alkyl-substituted ones, the adiabatic PESes were surfaces of pseudorotation due to avoided crossing. In the RCs studied, a correlation between the SLR rate and the calculated barrier height to the pseudorotation was revealed. For RCs with a higher relaxation rate, the apparent activation energies for the SLR were similar to the calculated heights of the barrier. To rationalize the data obtained it was assumed that the vibronic states degeneracy, which is specific for Jahn-Teller active cyclohexane RC, was approximately kept in the RCs of substituted cycloalkanes for the vibronic states with the energies above and close to the barrier height to the pseudorotation. It was proposed that the effective spin-lattice relaxation in a radical with nearly degenerate low-lying vibronic states originated from stochastic crossings of the vibronic levels that occur due to fluctuations of
Alonso, J L; Castro, A; Clemente-Gallardo, J; Echenique, P; Mazo, J J; Polo, V; Rubio, A; Zueco, D
2012-12-14
At non-zero temperature and when a system has low-lying excited electronic states, the ground-state Born-Oppenheimer approximation breaks down and the low-lying electronic states are involved in any chemical process. In this work, we use a temperature-dependent effective potential for the nuclei which can accommodate the influence of an arbitrary number of electronic states in a simple way, while at the same time producing the correct Boltzmann equilibrium distribution for the electronic part. With the help of this effective potential, we show that thermally activated low-lying electronic states can have a significant effect in molecular properties for which electronic excitations are oftentimes ignored. We study the thermal expansion of the Manganese dimer, Mn(2), where we find that the average bond length experiences a change larger than the present experimental accuracy upon the inclusion of the excited states into the picture. We also show that, when these states are taken into account, reaction-rate constants are modified. In particular, we study the opening of the ozone molecule, O(3), and show that in this case the rate is modified as much as a 20% with respect to the ground-state Born-Oppenheimer prediction. PMID:23249070
Adiabatic invariance of oscillons/I -balls
NASA Astrophysics Data System (ADS)
Kawasaki, Masahiro; Takahashi, Fuminobu; Takeda, Naoyuki
2015-11-01
Real scalar fields are known to fragment into spatially localized and long-lived solitons called oscillons or I -balls. We prove the adiabatic invariance of the oscillons/I -balls for a potential that allows periodic motion even in the presence of non-negligible spatial gradient energy. We show that such a potential is uniquely determined to be the quadratic one with a logarithmic correction, for which the oscillons/I -balls are absolutely stable. For slightly different forms of the scalar potential dominated by the quadratic one, the oscillons/I -balls are only quasistable, because the adiabatic charge is only approximately conserved. We check the conservation of the adiabatic charge of the I -balls in numerical simulation by slowly varying the coefficient of logarithmic corrections. This unambiguously shows that the longevity of oscillons/I -balls is due to the adiabatic invariance.
Zhu, Xiaolei; Malbon, Christopher L; Yarkony, David R
2016-03-28
In a recent work we constructed a quasi-diabatic representation, H(d), of the 1, 2, 3(1)A adiabatic states of phenol from high level multireference single and double excitation configuration interaction electronic structure data, energies, energy gradients, and derivative couplings. That H(d) accurately describes surface minima, saddle points, and also regions of strong nonadiabatic interactions, reproducing the locus of conical intersection seams and the coordinate dependence of the derivative couplings. The present work determines the accuracy of H(d) for describing phenol photodissociation. Additionally, we demonstrate that a modest energetic shift of two diabats yields a quantifiably more accurate H(d) compared with experimental energetics. The analysis shows that in favorable circumstances it is possible to use single point energies obtained from the most reliable electronic structure methods available, including methods for which the energy gradients and derivative couplings are not available, to improve the quality of a global representation of several coupled potential energy surfaces. Our data suggest an alternative interpretation of kinetic energy release measurements near λphot ∼ 248 nm. PMID:27036453
NASA Astrophysics Data System (ADS)
Zhu, Xiaolei; Malbon, Christopher L.; Yarkony, David R.
2016-03-01
In a recent work we constructed a quasi-diabatic representation, Hd, of the 1, 2, 31A adiabatic states of phenol from high level multireference single and double excitation configuration interaction electronic structure data, energies, energy gradients, and derivative couplings. That Hd accurately describes surface minima, saddle points, and also regions of strong nonadiabatic interactions, reproducing the locus of conical intersection seams and the coordinate dependence of the derivative couplings. The present work determines the accuracy of Hd for describing phenol photodissociation. Additionally, we demonstrate that a modest energetic shift of two diabats yields a quantifiably more accurate Hd compared with experimental energetics. The analysis shows that in favorable circumstances it is possible to use single point energies obtained from the most reliable electronic structure methods available, including methods for which the energy gradients and derivative couplings are not available, to improve the quality of a global representation of several coupled potential energy surfaces. Our data suggest an alternative interpretation of kinetic energy release measurements near λphot ˜ 248 nm.
Bhaskaran-Nair, Kiran; Kowalski, Karol; Jarrell, Mark; Moreno, Juana; Shelton, William A.
2015-11-05
Polyacenes have attracted considerable attention due to their use in organic based optoelectronic materials. Polyacenes are polycyclic aromatic hydrocarbons composed of fused benzene rings. Key to understanding and design of new functional materials is an understanding of their excited state properties starting with their electron affinity (EA) and ionization potential (IP). We have developed a highly accurate and com- putationally e*fficient EA/IP equation of motion coupled cluster singles and doubles (EA/IP-EOMCCSD) method that is capable of treating large systems and large basis set. In this study we employ the EA/IP-EOMCCSD method to calculate the electron affinity and ionization potential of naphthalene, anthracene, tetracene, pentacene, hex- acene and heptacene. We have compared our results with other previous theoretical studies and experimental data. Our EA/IP results are in very good agreement with experiment and when compared with the other theoretical investigations our results represent the most accurate calculations as compared to experiment.
Dolgounitcheva, O; Díaz-Tinoco, Manuel; Zakrzewski, V G; Richard, Ryan M; Marom, Noa; Sherrill, C David; Ortiz, J V
2016-02-01
Comparison of ab initio electron-propagator predictions of vertical ionization potentials and electron affinities of organic, acceptor molecules with benchmark calculations based on the basis set-extrapolated, coupled cluster single, double, and perturbative triple substitution method has enabled identification of self-energy approximations with mean, unsigned errors between 0.1 and 0.2 eV. Among the self-energy approximations that neglect off-diagonal elements in the canonical, Hartree-Fock orbital basis, the P3 method for electron affinities, and the P3+ method for ionization potentials provide the best combination of accuracy and computational efficiency. For approximations that consider the full self-energy matrix, the NR2 methods offer the best performance. The P3+ and NR2 methods successfully identify the correct symmetry label of the lowest cationic state in two cases, naphthalenedione and benzoquinone, where some other methods fail. PMID:26730459
The ionization potential of aqueous hydroxide computed using many-body perturbation theory
Opalka, Daniel Sprik, Michiel; Pham, Tuan Anh; Galli, Giulia
2014-07-21
The ionization potentials of electrolyte solutions provide important information about the electronic structure of liquids and solute-solvent interactions. We analyzed the positions of solute and solvent bands of aqueous hydroxide and the influence of the solvent environment on the ionization potential of hydroxide ions. We used the concept of a computational hydrogen electrode to define absolute band positions with respect to vacuum. We found that many-body perturbation theory in the G{sub 0} W{sub 0} approximation substantially improves the relative and absolute positions of the band edges of solute and solvent with respect to those obtained within Density Functional Theory, using semi-local functionals, yielding results in satisfactory agreement with recent experiments.
Bross, David H.; Parmar, Payal; Peterson, Kirk A.
2015-11-14
The first 6 ionization potentials (IPs) of the uranium atom have been calculated using multireference configuration interaction (MRCI+Q) with extrapolations to the complete basis set limit using new all-electron correlation consistent basis sets. The latter was carried out with the third-order Douglas-Kroll-Hess Hamiltonian. Correlation down through the 5s5p5d electrons has been taken into account, as well as contributions to the IPs due to the Lamb shift. Spin-orbit coupling contributions calculated at the 4-component Kramers restricted configuration interaction level, as well as the Gaunt term computed at the Dirac-Hartree-Fock level, were added to the best scalar relativistic results. The final ionization potentials are expected to be accurate to at least 5 kcal/mol (0.2 eV) and thus more reliable than the current experimental values of IP{sub 3} through IP{sub 6}.
Wireless adiabatic power transfer
Rangelov, A.A.; Suchowski, H.; Silberberg, Y.; Vitanov, N.V.
2011-03-15
Research Highlights: > Efficient and robust mid-range wireless energy transfer between two coils. > The adiabatic energy transfer is analogous to adiabatic passage in quantum optics. > Wireless energy transfer is insensitive to any resonant constraints. > Wireless energy transfer is insensitive to noise in the neighborhood of the coils. - Abstract: We propose a technique for efficient mid-range wireless power transfer between two coils, by adapting the process of adiabatic passage for a coherently driven two-state quantum system to the realm of wireless energy transfer. The proposed technique is shown to be robust to noise, resonant constraints, and other interferences that exist in the neighborhood of the coils.
Verma, Prakash; Bartlett, Rodney J.
2014-05-14
This paper's objective is to create a “consistent” mean-field based Kohn-Sham (KS) density functional theory (DFT) meaning the functional should not only provide good total energy properties, but also the corresponding KS eigenvalues should be accurate approximations to the vertical ionization potentials (VIPs) of the molecule, as the latter condition attests to the viability of the exchange-correlation potential (V{sub XC}). None of the prominently used DFT approaches show these properties: the optimized effective potential V{sub XC} based ab initio dft does. A local, range-separated hybrid potential cam-QTP-00 is introduced as the basis for a “consistent” KS DFT approach. The computed VIPs as the negative of KS eigenvalue have a mean absolute error of 0.8 eV for an extensive set of molecule's electron ionizations, including the core. Barrier heights, equilibrium geometries, and magnetic properties obtained from the potential are in good agreement with experiment. A similar accuracy with less computational efforts can be achieved by using a non-variational global hybrid variant of the QTP-00 approach.
NASA Astrophysics Data System (ADS)
Amendt, Peter; Ross, J. Steven; Milovich, Jose L.; Schneider, Marilyn; Storm, Erik; Callahan, Debra A.; Hinkel, Denise; Lasinski, Barbara; Meeker, Don; Michel, Pierre; Moody, John; Strozzi, David
2014-11-01
Rugby-shaped gold hohlraums driven by a nominal low-adiabat laser pulse shape have been tested on the National Ignition Facility. The rugby affords a higher coupling efficiency than a comparably sized cylinder hohlraum or, alternatively, improved drive symmetry and laser beam clearances for a larger hohlraum with similar cylinder wall area and laser energy. A first (large rugby hohlraum) shot at low energy (0.75 MJ) to test laser backscatter resulted in a moderately oblate CH capsule implosion, followed by a high energy shot (1.3 MJ) that gave a highly oblate compressed core according to both time-integrated and -resolved x-ray images. These implosions used low wavelength separation (1.0 Å) between the outer and inner cones to provide an alternative platform free of significant cross-beam energy transfer for simplified hohlraum dynamics. Post-shot 2- and 3-D radiation-hydrodynamic simulations using the high-flux model [M. D. Rosen et al., High Energy Density Phys. 7, 180 (2011)], however, give nearly round implosions for both shots, in striking contrast with observations. An analytic assessment of Rayleigh-Taylor hydrodynamic instability growth on the gold-helium gas-fill interface shows the potential for significant linear growth, saturation and transition to a highly nonlinear state. Candidate seeds for instability growth include laser speckle during the early-time laser picket episode in the presence of only partial temporal beam smoothing (1-D smoothing by spectral dispersion and polarization smoothing) and intensity modulations from quad-to-quad and beam overlap. Radiation-hydrodynamic 2-D simulations adapted to include a dynamic fall-line mix model across the unstable Au-He interface show good agreement with the observed implosion symmetry for both shots using an interface-to-fall-line penetration fraction of 100%. Physically, the potential development of an instability layer in a rugby hohlraum is tantamount to an enhanced wall motion leading to hindered
Amendt, Peter Ross, J. Steven; Milovich, Jose L.; Schneider, Marilyn; Storm, Erik; Callahan, Debra A.; Hinkel, Denise; Lasinski, Barbara; Meeker, Don; Michel, Pierre; Moody, John; Strozzi, David
2014-11-15
Rugby-shaped gold hohlraums driven by a nominal low-adiabat laser pulse shape have been tested on the National Ignition Facility. The rugby affords a higher coupling efficiency than a comparably sized cylinder hohlraum or, alternatively, improved drive symmetry and laser beam clearances for a larger hohlraum with similar cylinder wall area and laser energy. A first (large rugby hohlraum) shot at low energy (0.75 MJ) to test laser backscatter resulted in a moderately oblate CH capsule implosion, followed by a high energy shot (1.3 MJ) that gave a highly oblate compressed core according to both time-integrated and –resolved x-ray images. These implosions used low wavelength separation (1.0 Å) between the outer and inner cones to provide an alternative platform free of significant cross-beam energy transfer for simplified hohlraum dynamics. Post-shot 2- and 3-D radiation-hydrodynamic simulations using the high-flux model [M. D. Rosen et al., High Energy Density Phys. 7, 180 (2011)], however, give nearly round implosions for both shots, in striking contrast with observations. An analytic assessment of Rayleigh-Taylor hydrodynamic instability growth on the gold–helium gas-fill interface shows the potential for significant linear growth, saturation and transition to a highly nonlinear state. Candidate seeds for instability growth include laser speckle during the early-time laser picket episode in the presence of only partial temporal beam smoothing (1-D smoothing by spectral dispersion and polarization smoothing) and intensity modulations from quad-to-quad and beam overlap. Radiation-hydrodynamic 2-D simulations adapted to include a dynamic fall-line mix model across the unstable Au-He interface show good agreement with the observed implosion symmetry for both shots using an interface-to-fall-line penetration fraction of 100%. Physically, the potential development of an instability layer in a rugby hohlraum is tantamount to an enhanced wall motion leading to
NASA Technical Reports Server (NTRS)
Stallcop, James R.; Partridge, Harry; Levin, Eugene; Langhoff, Stephen R. (Technical Monitor)
1995-01-01
Collision integrals are fundamental quantities required to determine the transport properties of the environment surrounding aerospace vehicles in the upper atmosphere. These collision integrals can be determined as a function of temperature from the potential energy curves describing the atomic and molecular collisions. Ab initio calculations provide a practical method of computing the required interaction potentials. In this work we will discuss recent advances in scattering calculations with an emphasis on the accuracy that is obtainable. Results for interactions of the atoms and ionized atoms of nitrogen and oxygen will be reviewed and their application to the determination of transport properties, such as diffusion and viscosity coefficients, will be examined.
NASA Astrophysics Data System (ADS)
Gu, Quanli; Tang, Zhen; Su, Peifeng; Wu, Wei; Yang, Zhijun; Trindle, Carl O.; Knee, Joseph L.
2016-08-01
The ionization potential (IP) of the aromatic alpha hydroxy carboxylic acid, 9-hydroxy-9-fluorene carboxylic acid (9HFCA), is shifted by complexation with hydrogen bonding ligands such as water and formic acid. Generalized Kohn-Sham energy decomposition analysis decomposes the intermolecular binding energies into a frozen energy term, polarization, correlation, and/or dispersion energy terms, as well as terms of geometric relaxation and zero point energy. We observe that in each dimer the attractive polarization always increases upon ionization, enhancing binding in the cation and shifting the IP toward the red. For 9HFCA—H2O, a substantial decrease of the repulsive frozen energy in cation further shifts the IP toward red. For 9HFCA—HCOOH, the increase of the frozen energy actually occurs in the cation and shifts the IP toward blue. Consistent with the experimental measurements, our analysis provides new, non-intuitive perspectives on multiple hydrogen bonds interactions in carboxylic acids and water complexes.
Parallelizable adiabatic gate teleportation
NASA Astrophysics Data System (ADS)
Nakago, Kosuke; Hajdušek, Michal; Nakayama, Shojun; Murao, Mio
2015-12-01
To investigate how a temporally ordered gate sequence can be parallelized in adiabatic implementations of quantum computation, we modify adiabatic gate teleportation, a model of quantum computation proposed by Bacon and Flammia [Phys. Rev. Lett. 103, 120504 (2009), 10.1103/PhysRevLett.103.120504], to a form deterministically simulating parallelized gate teleportation, which is achievable only by postselection. We introduce a twisted Heisenberg-type interaction Hamiltonian, a Heisenberg-type spin interaction where the coordinates of the second qubit are twisted according to a unitary gate. We develop parallelizable adiabatic gate teleportation (PAGT) where a sequence of unitary gates is performed in a single step of the adiabatic process. In PAGT, numeric calculations suggest the necessary time for the adiabatic evolution implementing a sequence of L unitary gates increases at most as O (L5) . However, we show that it has the interesting property that it can map the temporal order of gates to the spatial order of interactions specified by the final Hamiltonian. Using this property, we present a controlled-PAGT scheme to manipulate the order of gates by a control qubit. In the controlled-PAGT scheme, two differently ordered sequential unitary gates F G and G F are coherently performed depending on the state of a control qubit by simultaneously applying the twisted Heisenberg-type interaction Hamiltonians implementing unitary gates F and G . We investigate why the twisted Heisenberg-type interaction Hamiltonian allows PAGT. We show that the twisted Heisenberg-type interaction Hamiltonian has an ability to perform a transposed unitary gate by just modifying the space ordering of the final Hamiltonian implementing a unitary gate in adiabatic gate teleportation. The dynamics generated by the time-reversed Hamiltonian represented by the transposed unitary gate enables deterministic simulation of a postselected event of parallelized gate teleportation in adiabatic
NASA Astrophysics Data System (ADS)
Bhaskaran-Nair, Kiran; Kowalski, Karol; Jarrell, Mark; Moreno, Juana; Shelton, William A.
2015-11-01
Polyacenes have attracted considerable attention due to their various applications in organic optoelectronic materials. This study focuses on linear polyacenes and their electron affinity (EA) and ionization potential (IP) properties. We have employed our recent implementation of EA/IP equation of motion coupled cluster singles and doubles (EA/IP-EOMCCSD) methods which are accurate, computationally efficient and are capable of treating large systems employing reasonable basis sets size. The EA/IP results obtained for naphthalene, anthracene, tetracene, pentacene, hexacene and heptacene are in a good agreement with experiment. Comparison between quality of excitation energies obtained from IP-EOMCCSD and EE-EOMCCSD formalisms were also studied.
Optical potential approach to the electron-atom impact ionization threshold problem
NASA Technical Reports Server (NTRS)
Temkin, A.; Hahn, Y.
1973-01-01
The problem of the threshold law for electron-atom impact ionization is reconsidered as an extrapolation of inelastic cross sections through the ionization threshold. The cross sections are evaluated from a distorted wave matrix element, the final state of which describes the scattering from the Nth excited state of the target atom. The actual calculation is carried for the e-H system, and a model is introduced which is shown to preserve the essential properties of the problem while at the same time reducing the dimensionability of the Schrodinger equation. Nevertheless, the scattering equation is still very complex. It is dominated by the optical potential which is expanded in terms of eigen-spectrum of QHQ. It is shown by actual calculation that the lower eigenvalues of this spectrum descend below the relevant inelastic thresholds; it follows rigorously that the optical potential contains repulsive terms. Analytical solutions of the final state wave function are obtained with several approximations of the optical potential.
Potential human study populations for non-ionizing (radio frequency) radiation health effects
Novotney, L.C.; Gravitis, I.
1982-12-01
This research project was initiated to identify potential human populations for future epidemiological studies of the health effects of radio frequency radiation. Through a literature search and contacts with various groups and organizations, numerous occupations and applications of radio frequency radiation (RFR) were identified and evaluated for their suitability for further study. Many populations were eliminated early because their potential exposure to RFR was too limited or data necessary for epidemiological research were unavailable. Eight populations were evaluated in detail and appear to satisfy many of the criteria for epidemiological research and could be useful study groups in an investigation of the health effects of non-ionizing radiation. The eight potential study populations are: RF heat sealer operators, HF (high frequency) tube welder operators, medical diathermy operators in Veterans Administration hospitals, medical diathermy operators in rehabilitation facilities, school children located near broadcasting towers, state policemen, security guards, and radar technicians.
Śmiga, Szymon; Della Sala, Fabio; Buksztel, Adam; Grabowski, Ireneusz; Fabiano, Eduardo
2016-08-15
One important property of Kohn-Sham (KS) density functional theory is the exact equality of the energy of the highest occupied KS orbital (HOMO) with the negative ionization potential of the system. This exact feature is out of reach for standard density-dependent semilocal functionals. Conversely, accurate results can be obtained using orbital-dependent functionals in the optimized effective potential (OEP) approach. In this article, we investigate the performance, in this context, of some advanced OEP methods, with special emphasis on the recently proposed scaled-opposite-spin OEP functional. Moreover, we analyze the impact of the so-called HOMO condition on the final quality of the HOMO energy. Results are compared to reference data obtained at the CCSD(T) level of theory. © 2016 Wiley Periodicals, Inc. PMID:27357413
NASA Astrophysics Data System (ADS)
Zhevstovskikh, I. V.; Bersuker, I. B.; Gudkov, V. V.; Averkiev, N. S.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Shakurov, G. S.; Ulanov, V. A.; Surikov, V. T.
2016-06-01
A methodology is worked out to retrieve the numerical values of all the main parameters of the six-dimensional adiabatic potential energy surface (APES) of a polyatomic system with a quadratic T-term Jahn-Teller effect (JTE) from the ultrasound experiments. The method is based on a verified assumption that ultrasound attenuation and speed encounter anomalies when the direction of propagation and polarization of its wave of strain coincides with the characteristic directions of symmetry breaking in the JTE. For the SrF2:Cr crystal, employed as a basic example, we observed anomaly peaks in the temperature dependence of attenuation of ultrasound at frequencies of 50-160 MHz in the temperature interval of 40-60 K for the wave propagating along the [110] direction, for both the longitudinal and the shear modes, the latter with two polarizations along the [001] and [1 1 ¯ 0 ] axes, respectively. We show that these anomalies are due to the ultrasound relaxation by the system of non-interacting Cr2+ JT centers with orthorhombic local distortions. The interpretation of the experimental findings is based on the T2 g⊗(eg+t2 g) JTE problem including the linear and the quadratic terms of vibronic interactions in the Hamiltonian and the same-symmetry modes reduced to one interaction mode. Combining the experimental results with a theoretical analysis, we show that on the complicated six-dimensional APES of this system with three tetragonal, four trigonal, and six orthorhombic extrema points, the latter are global minima, while the former are saddle points, and we estimate numerically all the main parameters of this surface, including the linear and quadratic vibronic coupling constants, the primary force constants, the coordinates of all the extrema points and their energies, the energy barrier between the orthorhombic minima, and the tunneling splitting of the ground vibrational states. To our knowledge, such a based-on-experimental-data numerical reconstruction of the APES
Adiabatic cooling of antiprotons.
Gabrielse, G; Kolthammer, W S; McConnell, R; Richerme, P; Kalra, R; Novitski, E; Grzonka, D; Oelert, W; Sefzick, T; Zielinski, M; Fitzakerley, D; George, M C; Hessels, E A; Storry, C H; Weel, M; Müllers, A; Walz, J
2011-02-18
Adiabatic cooling is shown to be a simple and effective method to cool many charged particles in a trap to very low temperatures. Up to 3×10(6) p are cooled to 3.5 K-10(3) times more cold p and a 3 times lower p temperature than previously reported. A second cooling method cools p plasmas via the synchrotron radiation of embedded e(-) (with many fewer e(-) than p in preparation for adiabatic cooling. No p are lost during either process-a significant advantage for rare particles. PMID:21405511
Adiabatic Cooling of Antiprotons
Gabrielse, G.; Kolthammer, W. S.; McConnell, R.; Richerme, P.; Kalra, R.; Novitski, E.; Oelert, W.; Grzonka, D.; Sefzick, T.; Zielinski, M.; Fitzakerley, D.; George, M. C.; Hessels, E. A.; Storry, C. H.; Weel, M.; Muellers, A.; Walz, J.
2011-02-18
Adiabatic cooling is shown to be a simple and effective method to cool many charged particles in a trap to very low temperatures. Up to 3x10{sup 6} p are cooled to 3.5 K--10{sup 3} times more cold p and a 3 times lower p temperature than previously reported. A second cooling method cools p plasmas via the synchrotron radiation of embedded e{sup -} (with many fewer e{sup -} than p) in preparation for adiabatic cooling. No p are lost during either process--a significant advantage for rare particles.
A hierarchy of local coupled cluster singles and doubles response methods for ionization potentials
NASA Astrophysics Data System (ADS)
Wälz, Gero; Usvyat, Denis; Korona, Tatiana; Schütz, Martin
2016-02-01
We present a hierarchy of local coupled cluster (CC) linear response (LR) methods to calculate ionization potentials (IPs), i.e., excited states with one electron annihilated relative to a ground state reference. The time-dependent perturbation operator V(t), as well as the operators related to the first-order (with respect to V(t)) amplitudes and multipliers, thus are not number conserving and have half-integer particle rank m. Apart from calculating IPs of neutral molecules, the method offers also the possibility to study ground and excited states of neutral radicals as ionized states of closed-shell anions. It turns out that for comparable accuracy IPs require a higher-order treatment than excitation energies; an IP-CC LR method corresponding to CC2 LR or the algebraic diagrammatic construction scheme through second order performs rather poorly. We therefore systematically extended the order with respect to the fluctuation potential of the IP-CC2 LR Jacobian up to IP-CCSD LR, keeping the excitation space of the first-order (with respect to V(t)) cluster operator restricted to the m = /1 2 ⊕ /3 2 subspace and the accuracy of the zero-order (ground-state) amplitudes at the level of CC2 or MP2. For the more expensive diagrams beyond the IP-CC2 LR Jacobian, we employ local approximations. The implemented methods are capable of treating large molecular systems with hundred atoms or more.
Bross, David H.; Parmar, Payal; Peterson, Kirk A.
2015-11-12
The first 6 ionization potentials (IPs) of the uranium atom have been calculated using multireference configuration interaction (MRCI+Q) with extrapolations to the complete basis set (CBS) limit using new all-electron correlation consistent basis sets. The latter were carried out with the third-order Douglas-Kroll-Hess Hamiltonian. Correlation down through the 5s5p5d electrons have been taken into account, as well as contributions to the IPs due to the Lamb shift. Spin-orbit coupling contributions calculated at the 4-component Kramers restricted configuration interaction level, as well as the Gaunt term computed at the Dirac-Hartree-Fock level, were added to the best scalar relativistic results. As a result, the final ionization potentials are expected to be accurate to at least 5 kcal/mol (0.2 eV), and thus more reliable than the current experimental values of IP_{3} through IP_{6}.
Bross, David H.; Parmar, Payal; Peterson, Kirk A.
2015-11-12
The first 6 ionization potentials (IPs) of the uranium atom have been calculated using multireference configuration interaction (MRCI+Q) with extrapolations to the complete basis set (CBS) limit using new all-electron correlation consistent basis sets. The latter were carried out with the third-order Douglas-Kroll-Hess Hamiltonian. Correlation down through the 5s5p5d electrons have been taken into account, as well as contributions to the IPs due to the Lamb shift. Spin-orbit coupling contributions calculated at the 4-component Kramers restricted configuration interaction level, as well as the Gaunt term computed at the Dirac-Hartree-Fock level, were added to the best scalar relativistic results. As amore » result, the final ionization potentials are expected to be accurate to at least 5 kcal/mol (0.2 eV), and thus more reliable than the current experimental values of IP3 through IP6.« less
Giardi, Maria Teresa; Touloupakis, Eleftherios; Bertolotto, Delfina; Mascetti, Gabriele
2013-01-01
Humans are constantly exposed to ionizing radiation deriving from outer space sources or activities related to medical care. Absorption of ionizing radiation doses over a prolonged period of time can result in oxidative damage and cellular dysfunction inducing several diseases, especially in ageing subjects. In this report, we analyze the effects of ionizing radiation, particularly at low doses, in relation to a variety of human pathologies, including cancer, and cardiovascular and retinal diseases. We discuss scientific data in support of protection strategies by safe antioxidant formulations that can provide preventive or potential therapeutic value in response to long-term diseases that may develop following exposure. PMID:23965979
Adiabatically implementing quantum gates
Sun, Jie; Lu, Songfeng Liu, Fang
2014-06-14
We show that, through the approach of quantum adiabatic evolution, all of the usual quantum gates can be implemented efficiently, yielding running time of order O(1). This may be considered as a useful alternative to the standard quantum computing approach, which involves quantum gates transforming quantum states during the computing process.
Entanglement and adiabatic quantum computation
NASA Astrophysics Data System (ADS)
Ahrensmeier, D.
2006-06-01
Adiabatic quantum computation provides an alternative approach to quantum computation using a time-dependent Hamiltonian. The time evolution of entanglement during the adiabatic quantum search algorithm is studied, and its relevance as a resource is discussed.
High-field plasma acceleration in a high-ionization-potential gas
NASA Astrophysics Data System (ADS)
Corde, S.; Adli, E.; Allen, J. M.; An, W.; Clarke, C. I.; Clausse, B.; Clayton, C. E.; Delahaye, J. P.; Frederico, J.; Gessner, S.; Green, S. Z.; Hogan, M. J.; Joshi, C.; Litos, M.; Lu, W.; Marsh, K. A.; Mori, W. B.; Vafaei-Najafabadi, N.; Walz, D.; Yakimenko, V.
2016-06-01
Plasma accelerators driven by particle beams are a very promising future accelerator technology as they can sustain high accelerating fields over long distances with high energy efficiency. They rely on the excitation of a plasma wave in the wake of a drive beam. To generate the plasma, a neutral gas can be field-ionized by the head of the drive beam, in which case the distance of acceleration and energy gain can be strongly limited by head erosion. Here we overcome this limit and demonstrate that electrons in the tail of a drive beam can be accelerated by up to 27 GeV in a high-ionization-potential gas (argon), boosting their initial 20.35 GeV energy by 130%. Particle-in-cell simulations show that the argon plasma is sustaining very high electric fields, of ~150 GV m-1, over ~20 cm. The results open new possibilities for the design of particle beam drivers and plasma sources.
High-field plasma acceleration in a high-ionization-potential gas
Corde, S.; Adli, E.; Allen, J. M.; An, W.; Clarke, C. I.; Clausse, B.; Clayton, C. E.; Delahaye, J. P.; Frederico, J.; Gessner, S.; Green, S. Z.; Hogan, M. J.; Joshi, C.; Litos, M.; Lu, W.; Marsh, K. A.; Mori, W. B.; Vafaei-Najafabadi, N.; Walz, D.; Yakimenko, V.
2016-01-01
Plasma accelerators driven by particle beams are a very promising future accelerator technology as they can sustain high accelerating fields over long distances with high energy efficiency. They rely on the excitation of a plasma wave in the wake of a drive beam. To generate the plasma, a neutral gas can be field-ionized by the head of the drive beam, in which case the distance of acceleration and energy gain can be strongly limited by head erosion. Here we overcome this limit and demonstrate that electrons in the tail of a drive beam can be accelerated by up to 27 GeV in a high-ionization-potential gas (argon), boosting their initial 20.35 GeV energy by 130%. Particle-in-cell simulations show that the argon plasma is sustaining very high electric fields, of ∼150 GV m−1, over ∼20 cm. The results open new possibilities for the design of particle beam drivers and plasma sources. PMID:27312720
High-field plasma acceleration in a high-ionization-potential gas.
Corde, S; Adli, E; Allen, J M; An, W; Clarke, C I; Clausse, B; Clayton, C E; Delahaye, J P; Frederico, J; Gessner, S; Green, S Z; Hogan, M J; Joshi, C; Litos, M; Lu, W; Marsh, K A; Mori, W B; Vafaei-Najafabadi, N; Walz, D; Yakimenko, V
2016-01-01
Plasma accelerators driven by particle beams are a very promising future accelerator technology as they can sustain high accelerating fields over long distances with high energy efficiency. They rely on the excitation of a plasma wave in the wake of a drive beam. To generate the plasma, a neutral gas can be field-ionized by the head of the drive beam, in which case the distance of acceleration and energy gain can be strongly limited by head erosion. Here we overcome this limit and demonstrate that electrons in the tail of a drive beam can be accelerated by up to 27 GeV in a high-ionization-potential gas (argon), boosting their initial 20.35 GeV energy by 130%. Particle-in-cell simulations show that the argon plasma is sustaining very high electric fields, of ∼150 GV m(-1), over ∼20 cm. The results open new possibilities for the design of particle beam drivers and plasma sources. PMID:27312720
High-field plasma acceleration in a high-ionization-potential gas
Corde, S.; Adli, E.; Allen, J. M.; An, W.; Clarke, C. I.; Clausse, B.; Clayton, C. E.; Delahaye, J. P.; Frederico, J.; Gessner, S.; et al
2016-06-17
Plasma accelerators driven by particle beams are a very promising future accelerator technology as they can sustain high accelerating fields over long distances with high energy efficiency. They rely on the excitation of a plasma wave in the wake of a drive beam. To generate the plasma, a neutral gas can be field-ionized by the head of the drive beam, in which case the distance of acceleration and energy gain can be strongly limited by head erosion. In our research, we overcome this limit and demonstrate that electrons in the tail of a drive beam can be accelerated by upmore » to 27 GeV in a high-ionization-potential gas (argon), boosting their initial 20.35 GeV energy by 130%. Particle-in-cell simulations show that the argon plasma is sustaining very high electric fields, of ~150 GV m-1, over ~20 cm. Lastly, the results open new possibilities for the design of particle beam drivers and plasma sources.« less
NASA Technical Reports Server (NTRS)
Laming, J. Martin; Drake, J. J.; Widing, Kenneth G.
1995-01-01
In this paper we reanalayze the full-disk quiet-sun spectrum of Mallinovsky & Heroux (1973) with modern atomic data. The purposes of this are to check our atomic data and methods in other investigations using data from nearby stars obtained with the NASA Extreme Ultraviolet Explorer (EUVE) satellite, and to confirm that the solar first ionization potential (FIP) effect investigated by previous authors studying discrete solar regions is the same as that found in full-disk spectra. We recover the usual solar FIP effect of a coronal abundance enhancement of elements with a low FIP of a factor approximately 3-4 for lines formed at temperatures greater than approximately 10(exp 6) K. For lower temperatures, the FIP effect seems to be substantially smaller, in qualitative agreement with other data. Comparing our full-disk result with those from discrete solar structures suggest that the FIP effect is a function of altitude, with the lower temperature full-disk emission being dominated by the super-granulation network. We also compare the recent ionization balance of Arnaud & Raymond (1992) with that of Arnaud & Rothenflug (1985).
Gu, Quanli; Tang, Zhen; Su, Peifeng; Wu, Wei; Yang, Zhijun; Trindle, Carl O; Knee, Joseph L
2016-08-01
The ionization potential (IP) of the aromatic alpha hydroxy carboxylic acid, 9-hydroxy-9-fluorene carboxylic acid (9HFCA), is shifted by complexation with hydrogen bonding ligands such as water and formic acid. Generalized Kohn-Sham energy decomposition analysis decomposes the intermolecular binding energies into a frozen energy term, polarization, correlation, and/or dispersion energy terms, as well as terms of geometric relaxation and zero point energy. We observe that in each dimer the attractive polarization always increases upon ionization, enhancing binding in the cation and shifting the IP toward the red. For 9HFCA-H2O, a substantial decrease of the repulsive frozen energy in cation further shifts the IP toward red. For 9HFCA-HCOOH, the increase of the frozen energy actually occurs in the cation and shifts the IP toward blue. Consistent with the experimental measurements, our analysis provides new, non-intuitive perspectives on multiple hydrogen bonds interactions in carboxylic acids and water complexes. PMID:27497532
NON-WKB MODELS OF THE FIRST IONIZATION POTENTIAL EFFECT: THE ROLE OF SLOW MODE WAVES
Laming, J. Martin
2012-01-10
A model for element abundance fractionation between the solar chromosphere and corona is further developed. The ponderomotive force due to Alfven waves propagating through or reflecting from the chromosphere in solar conditions generally accelerates chromospheric ions, but not neutrals, into the corona. This gives rise to what has become known as the first ionization potential effect. We incorporate new physical processes into the model. The chromospheric ionization balance is improved and the effect of different approximations is discussed. We also treat the parametric generation of slow mode waves by the parallel propagating Alfven waves. This is also an effect of the ponderomotive force, arising from the periodic variation of the magnetic pressure driving an acoustic mode, which adds to the background longitudinal pressure. This can have subtle effects on the fractionation, rendering it quasi-mass independent in the lower regions of the chromosphere. We also briefly discuss the change in the fractionation with Alfven wave frequency, relative to the frequency of the overlying coronal loop resonance.
Jursic, B.S.
1996-12-31
Up to four ionization potentials of elements from the second-row of the periodic table were computed using the ab initio (HF, MP2, MP3, MP4, QCISD, GI, G2, and G2MP2) and DFT (B3LY, B3P86, B3PW91, XALPHA, HFS, HFB, BLYP, BP86, BPW91, BVWN, XAPLY, XAP86, XAPW91, XAVWN, SLYR SP86, SPW91 and SVWN) methods. In all of the calculations, the large 6-311++G(3df,3pd) gaussian type of basis set was used. The computed values were compared with the experimental results and suitability of the ab initio and DFF methods were discussed, in regard to reproducing the experimental data. From the computed ionization potentials of the second-row elements, it can be concluded that the HF ab initio computation is not capable of reproducing the experimental results. The computed ionization potentials are too low. However, by using the ab initio methods that include electron correlation, the computed IPs are becoming much closer to the experimental values. In all cases, with the exception of the first ionization potential for oxygen, the G2 computation result produces ionization potentials that are indistinguishable from the experimental results.
Ionization potential of {sup 9}Be calculated including nuclear motion and relativistic corrections
Stanke, Monika; Kedziera, Dariusz; Bubin, Sergiy; Adamowicz, Ludwik
2007-05-15
Variational calculations employing explicitly correlated Gaussian functions have been performed for the ground states of {sup 9}Be and {sup 9}Be{sup +} including the nuclear motion [i.e., without assuming the Born-Oppenheimer (BO) approximation]. An approach based on the analytical energy gradient calculated with respect to the Gaussian exponential parameters was employed, leading to energies of the two systems noticeably improved over those found in the recent paper of Pachucki and Komasa [Phys. Rev. A 73, 052502 (2006)]. The non-BO wave functions were used to calculate the {alpha}{sup 2} relativistic corrections ({alpha}=e{sup 2}/({Dirac_h}/2{pi})c). With those corrections and the {alpha}{sup 3} and {alpha}{sup 4} corrections taken from Pachucki and Komasa, a new value of the ionization potential (IP) of {sup 9}Be was determined. It agrees very well with the most recent experimental IP.
NASA Astrophysics Data System (ADS)
Kang, Youngho; Jeon, Sang Ho; Cho, Youngmi; Han, Seungwu
2016-01-01
We investigate the vertical ionization potential (IP) and electron affinity (EA) of organic semiconductors in the solid state that govern the optoelectrical property of organic devices using a fully ab initio way. The present method combines the density functional theory and many-body perturbation theory based on G W approximations. To demonstrate the accuracy of this approach, we carry out calculations on several prototypical organic molecules. Since IP and EA depend on the molecular orientation at the surface, the molecular geometry of the surface is explicitly considered through the slab model. The computed IP and EA are in reasonable and consistent agreements with spectroscopic data on organic surfaces with various molecular arrangements. However, the transport gaps are slightly underestimated in calculations, which can be explained by different screening effects between surface and bulk regions.
Role of the ionization potential in nonequilibrium metals driven to absorption saturation
NASA Astrophysics Data System (ADS)
Mincigrucci, R.; Bencivenga, F.; Capotondi, F.; Principi, E.; Giangrisostomi, E.; Battistoni, A.; Caputo, M.; Casolari, F.; Gessini, A.; Manfredda, M.; Pedersoli, E.; Masciovecchio, C.
2015-07-01
A composite metallic foil (Al/Mg/Al) has been exposed to intense sub-100 fs free electron laser (FEL) pulses and driven to ultrafast massive photoionization. The resulting nonequilibrium state of matter has been monitored through absorption spectroscopy across the L2 ,3 edge of Mg as a function of the FEL fluence. The raw spectroscopic data indicate that at about 100 J /cm2 the main absorption channels of the sample, i.e., Mg (2 p →free ) and oxidized Al (valence→free ), are almost saturated. The spectral behavior of the induced transparency has been interpreted with an analytical approach based on an effective ionization potential of the generated solid-density plasma.
NASA Astrophysics Data System (ADS)
Shestakova, L. I.
2015-04-01
Calculated results are presented for solar radiation pressure acting on atoms and first ions. For some of these particles, radiation pressure exceeds the gravitational attraction and can accelerate them to large velocities. A comparison of the results with ionization potentials shows that the maxima of radiation pressure on neutral atoms coincide with the minima of the first ionization potentials (FIPs). This relationship is even more apparent for first ions. The minima of the second ionization potentials (SIPs) coincide with the radiation pressure maxima for a number of ions such as Be II, Mg II, Ca II, and the neighboring elements. Thus, radiation pressure may serve as a possible mechanism of acceleration of pickup ions and energetic neutral atoms (ENA) coming from an inner source (zodiacal dust and sungrazing comets). These atoms and ions, which are not typical of the solar wind, are formed as a result of the disintegration of comets or meteor showers near the Sun and can accelerate and reach the Earth's orbit as part of the solar wind. Doubly ionized atoms have resonance lines in the UV range, where solar radiation pressure has no apparent impact on the particle dynamics; thus, the proposed acceleration mechanism can only be applied to neutral atoms and first ions with low potentials of the subsequent ionization.
Adiabatic topological quantum computing
NASA Astrophysics Data System (ADS)
Cesare, Chris; Landahl, Andrew J.; Bacon, Dave; Flammia, Steven T.; Neels, Alice
2015-07-01
Topological quantum computing promises error-resistant quantum computation without active error correction. However, there is a worry that during the process of executing quantum gates by braiding anyons around each other, extra anyonic excitations will be created that will disorder the encoded quantum information. Here, we explore this question in detail by studying adiabatic code deformations on Hamiltonians based on topological codes, notably Kitaev's surface codes and the more recently discovered color codes. We develop protocols that enable universal quantum computing by adiabatic evolution in a way that keeps the energy gap of the system constant with respect to the computation size and introduces only simple local Hamiltonian interactions. This allows one to perform holonomic quantum computing with these topological quantum computing systems. The tools we develop allow one to go beyond numerical simulations and understand these processes analytically.
Accurate adiabatic correction in the hydrogen molecule
Pachucki, Krzysztof; Komasa, Jacek
2014-12-14
A new formalism for the accurate treatment of adiabatic effects in the hydrogen molecule is presented, in which the electronic wave function is expanded in the James-Coolidge basis functions. Systematic increase in the size of the basis set permits estimation of the accuracy. Numerical results for the adiabatic correction to the Born-Oppenheimer interaction energy reveal a relative precision of 10{sup −12} at an arbitrary internuclear distance. Such calculations have been performed for 88 internuclear distances in the range of 0 < R ⩽ 12 bohrs to construct the adiabatic correction potential and to solve the nuclear Schrödinger equation. Finally, the adiabatic correction to the dissociation energies of all rovibrational levels in H{sub 2}, HD, HT, D{sub 2}, DT, and T{sub 2} has been determined. For the ground state of H{sub 2} the estimated precision is 3 × 10{sup −7} cm{sup −1}, which is almost three orders of magnitude higher than that of the best previous result. The achieved accuracy removes the adiabatic contribution from the overall error budget of the present day theoretical predictions for the rovibrational levels.
Accurate adiabatic correction in the hydrogen molecule
NASA Astrophysics Data System (ADS)
Pachucki, Krzysztof; Komasa, Jacek
2014-12-01
A new formalism for the accurate treatment of adiabatic effects in the hydrogen molecule is presented, in which the electronic wave function is expanded in the James-Coolidge basis functions. Systematic increase in the size of the basis set permits estimation of the accuracy. Numerical results for the adiabatic correction to the Born-Oppenheimer interaction energy reveal a relative precision of 10-12 at an arbitrary internuclear distance. Such calculations have been performed for 88 internuclear distances in the range of 0 < R ⩽ 12 bohrs to construct the adiabatic correction potential and to solve the nuclear Schrödinger equation. Finally, the adiabatic correction to the dissociation energies of all rovibrational levels in H2, HD, HT, D2, DT, and T2 has been determined. For the ground state of H2 the estimated precision is 3 × 10-7 cm-1, which is almost three orders of magnitude higher than that of the best previous result. The achieved accuracy removes the adiabatic contribution from the overall error budget of the present day theoretical predictions for the rovibrational levels.
NASA Technical Reports Server (NTRS)
Mullan, D. J.
1985-01-01
The first ionization potential (FIP) ordering of elemental abundances in solar energetic particles and in the corona which can both be explained Coulomb effects is discussed. Solar energetic particles (SEP) and coronal gas have anomalous abundances relative to the photosphere. The anomalies are similar in both cases: which led to the conclusion that SEP acceleration is not selective, but merely preserves the source abundances. It is argued that SEP acceleration can be selective, because identical selectivity operates to determine the coronal abundances. The abundance anomalies are ordered by first ionization potential (FIP).
Anders, André; Ni, Pavel; Panjan, Matjaž; Franz, Robert; Andersson, Joakim
2013-09-30
Ion energy distribution functions measured for high power impulse magnetron sputtering show features, such as a broad peak at several 10 eV with an extended tail, as well as asymmetry with respect to E×B, where E and B are the local electric and magnetic field vectors, respectively. Here it is proposed that those features are due to the formation of a potential hump of several 10 V in each of the traveling ionization zones. Potential hump formation is associated with a negative-positive-negative space charge that naturally forms in ionization zones driven by energetic drifting electrons.
NASA Astrophysics Data System (ADS)
Kessler, T.; Brück, K.; Baktash, C.; Beene, J. R.; Geppert, Ch; Havener, C. C.; Krause, H. F.; Liu, Y.; Schultz, D. R.; Stracener, D. W.; Vane, C. R.; Wendt, K.
2007-12-01
In preparation of a laser ion source, we have investigated multi-step laser ionization via Rydberg and autoionizing states for atomic Ni and Ge using a mass separator with an ion beam energy of 20 keV. For both elements resonant three-step excitation schemes suitable for modern Ti:sapphire laser systems were developed. Rydberg series in the range of principal quantum numbers 20 <= n <= 80 were localized, assigned and quantum numbers were allocated to the individual resonances. Ionization potentials (IP) were extracted from fits of the individual series and quantum defects of individual levels were analysed for confirmation of series assignment. For Ni the ionization potential could be extracted with significantly increased precision compared to literature with a value of EIP (Ni) = 61 619.77(14) cm-1. Also, at least one notable autoionizing state above the first IP was discovered for both elements, and the different ionization schemes via Rydberg or autoionizing states were compared with respect to line shape, ionization efficiency and selectivity.
Vertical Ionization Potentials of Nucleobases in a Fully Solvated DNA Environment
Cauet, Emilie L.; Valiev, Marat; Weare, John H.
2010-05-06
Calculations of the direct ionization potentials (DIP) of DNA nucleobases in the fully solvated DNA helix are reported. The results show an unexpected large shift of roughly 3.2-3.3 eV compared to the corresponding gas-phase IP values. The DIP shift is nearly the same for all the four DNA bases and appears to vary slowly with the stacking and H-bonding interactions of the nucleobases. We demonstrate that the large shift in the DIP of bases is due to the electric potential around the DNA resulting from the long range solvent structure created by the negative phosphate groups and positive counterions of the DNA helical structure. Thermal fluctuations in the fluid can result in DIP changes of roughly 1ev on a picosecond time scale. The model used in this work is based on a QM/MM approach in which the base (or clusters of bases) are chosen as the QM system and calculated using a high-level quantum chemistry method. The remaining DNA fragment and the species in solution are included in an exact molecular mechanics (MM) model. The expected high accuracy of the QM/MM model is defended in terms of the essentially Columbic nature of the interactions of the solvent (the MM region) with isolated base in the quantum region. For the test anion, Cl-, the QM/MM approach yields the 3.4 eV (gas-phase) to 9.3 eV (aqueous solution) shift of the ionization energy in agreement with experimental values (3.6 and 9.6 eV). The localization of the electronic excitation inside the QM region is supported by current experimental and theoretical evidence indicating that the HOMO of the nucleotide is localized on the base rather than the sugar or the phosphate backbone. Our calculations performed in the native DNA environment support this localization. The QM/MM model presented in this work provides an important simplification to the difficult problem of incorporating a detailed structural model of the physiological conditions into investigations of the electronic processes in DNA.
Technology Transfer Automated Retrieval System (TEKTRAN)
The administration of primaquine (PQ), an essential drug for treatment and radical cure of malaria, can lead to methemoglobin formation and life-threatening hemolysis for glucose-6-phosphate dehydrogenase deficient patients. The ionization potential (IP, a quantitative measure of the ability to lose...
Bazzani, A.; Turchetti, G.; Benedetti, C.; Rambaldi, S.; Servizi, G.
2005-06-08
In a high intensity circular accelerator the synchrotron dynamics introduces a slow modulation in the betatronic tune due to the space-charge tune depression. When the transverse motion is non-linear due to the presence of multipolar effects, resonance islands move in the phase space and change their amplitude. This effect introduces the trapping and detrapping phenomenon and a slow diffusion in the phase space. We apply the neo-adiabatic theory to describe this diffusion mechanism that can contribute to halo formation.
NASA Astrophysics Data System (ADS)
Ali, S.; Nasim, M. H.; Murtaza, G.
2003-11-01
The expressions for the Debye and the wake potential are derived by incorporating dust-charge fluctuations of a single projectile, as well as of an array of dust grain projectiles, propagating through a partially ionized dusty plasma with a constant velocity. Numerically, the effects of the dust-charge fluctuations and the dust-neutral collisions on the electrostatic potential for a single, three, six and ten projectiles are examined. The dust-charge relaxation rate modifies the shape of the Debye as well as the wake potential. For smaller values of the relaxation rates a potential well is formed instead of Debye potential.
Knight, Joseph W; Wang, Xiaopeng; Gallandi, Lukas; Dolgounitcheva, Olga; Ren, Xinguo; Ortiz, J Vincent; Rinke, Patrick; Körzdörfer, Thomas; Marom, Noa
2016-02-01
The performance of different GW methods is assessed for a set of 24 organic acceptors. Errors are evaluated with respect to coupled cluster singles, doubles, and perturbative triples [CCSD(T)] reference data for the vertical ionization potentials (IPs) and electron affinities (EAs), extrapolated to the complete basis set limit. Additional comparisons are made to experimental data, where available. We consider fully self-consistent GW (scGW), partial self-consistency in the Green's function (scGW0), non-self-consistent G0W0 based on several mean-field starting points, and a "beyond GW" second-order screened exchange (SOSEX) correction to G0W0. We also describe the implementation of the self-consistent Coulomb hole with screened exchange method (COHSEX), which serves as one of the mean-field starting points. The best performers overall are G0W0+SOSEX and G0W0 based on an IP-tuned long-range corrected hybrid functional with the former being more accurate for EAs and the latter for IPs. Both provide a balanced treatment of localized vs delocalized states and valence spectra in good agreement with photoemission spectroscopy (PES) experiments. PMID:26731609
Quantum-Mechanical Calculation of Ionization-Potential Lowering in Dense Plasmas
NASA Astrophysics Data System (ADS)
Son, Sang-Kil; Thiele, Robert; Jurek, Zoltan; Ziaja, Beata; Santra, Robin
2014-07-01
The charged environment within a dense plasma leads to the phenomenon of ionization-potential depression (IPD) for ions embedded in the plasma. Accurate predictions of the IPD effect are of crucial importance for modeling atomic processes occurring within dense plasmas. Several theoretical models have been developed to describe the IPD effect, with frequently discrepant predictions. Only recently, first experiments on IPD in Al plasma have been performed with an x-ray free-electron laser, where their results were found to be in disagreement with the widely used IPD model by Stewart and Pyatt. Another experiment on Al, at the Orion laser, showed disagreement with the model by Ecker and Kröll. This controversy shows a strong need for a rigorous and consistent theoretical approach to calculate the IPD effect. Here, we propose such an approach: a two-step Hartree-Fock-Slater model. With this parameter-free model, we can accurately and efficiently describe the experimental Al data and validate the accuracy of standard IPD models. Our model can be a useful tool for calculating atomic properties within dense plasmas with wide-ranging applications to studies on warm dense matter, shock experiments, planetary science, inertial confinement fusion, and nonequilibrium plasmas created with x-ray free-electron lasers.
NASA Astrophysics Data System (ADS)
Sun, Haitao; Tang, Ke; Li, Yanmin; Su, Chunfang; Zhou, Zhengyu; Wang, Zhizhong
The effect of hydrogen bond interactions on ionization potentials (IPs) and electron affinities (EAs) of thymine-formamide complexes (T-F) have been investigated employing the density functional theory B3LYP at 6-311++G(d, p) basis set level. All complexes experience a geometrical change on either electron detachment or attachment, and the change might be facilitated or hindered according to the strength of the hydrogen-bonding interaction involved. The strength of hydrogen bonds presents an opposite changing trend on the two processes. A more important role that H-bonding interaction plays in the process of electron attachment than in the process of electron detachment can be seen by a comparison of the IPs and EAs of complexes with that of isolated thymine. Futhermore, the EAs of isolated thymine are in good agreement with the experimental values (AEA is 0.79 eV, VEA is -0.29 eV [Wetmore et al., Chem Phys Lett 2000, 322, 129]). The calculated total NPA charge distributions reveal that nearly all the negative charges locate on thymine monomer in the anions and even in the cationic states, there are a few negative charges on thymine monomer. An analysis of dissociation energies predicts the processes T-F+→ T++ F and T-F- → T- + F to be the most energetically favorable for T-F+ and T-F-, respectively. Content:text/plain; charset="UTF-8"
An integrated programming and development environment for adiabatic quantum optimization
NASA Astrophysics Data System (ADS)
Humble, T. S.; McCaskey, A. J.; Bennink, R. S.; Billings, J. J.; DʼAzevedo, E. F.; Sullivan, B. D.; Klymko, C. F.; Seddiqi, H.
2014-01-01
Adiabatic quantum computing is a promising route to the computational power afforded by quantum information processing. The recent availability of adiabatic hardware has raised challenging questions about how to evaluate adiabatic quantum optimization (AQO) programs. Processor behavior depends on multiple steps to synthesize an adiabatic quantum program, which are each highly tunable. We present an integrated programming and development environment for AQO called Jade Adiabatic Development Environment (JADE) that provides control over all the steps taken during program synthesis. JADE captures the workflow needed to rigorously specify the AQO algorithm while allowing a variety of problem types, programming techniques, and processor configurations. We have also integrated JADE with a quantum simulation engine that enables program profiling using numerical calculation. The computational engine supports plug-ins for simulation methodologies tailored to various metrics and computing resources. We present the design, integration, and deployment of JADE and discuss its potential use for benchmarking AQO programs by the quantum computer science community.
NASA Astrophysics Data System (ADS)
Landahl, Andrew
2012-10-01
Quantum computers promise to exploit counterintuitive quantum physics principles like superposition, entanglement, and uncertainty to solve problems using fundamentally fewer steps than any conventional computer ever could. The mere possibility of such a device has sharpened our understanding of quantum coherent information, just as lasers did for our understanding of coherent light. The chief obstacle to developing quantum computer technology is decoherence--one of the fastest phenomena in all of physics. In principle, decoherence can be overcome by using clever entangled redundancies in a process called fault-tolerant quantum error correction. However, the quality and scale of technology required to realize this solution appears distant. An exciting alternative is a proposal called ``adiabatic'' quantum computing (AQC), in which adiabatic quantum physics keeps the computer in its lowest-energy configuration throughout its operation, rendering it immune to many decoherence sources. The Adiabatic Quantum Architectures In Ultracold Systems (AQUARIUS) Grand Challenge Project at Sandia seeks to demonstrate this robustness in the laboratory and point a path forward for future hardware development. We are building devices in AQUARIUS that realize the AQC architecture on up to three quantum bits (``qubits'') in two platforms: Cs atoms laser-cooled to below 5 microkelvin and Si quantum dots cryo-cooled to below 100 millikelvin. We are also expanding theoretical frontiers by developing methods for scalable universal AQC in these platforms. We have successfully demonstrated operational qubits in both platforms and have even run modest one-qubit calculations using our Cs device. In the course of reaching our primary proof-of-principle demonstrations, we have developed multiple spinoff technologies including nanofabricated diffractive optical elements that define optical-tweezer trap arrays and atomic-scale Si lithography commensurate with placing individual donor atoms with
Geometry of the Adiabatic Theorem
ERIC Educational Resources Information Center
Lobo, Augusto Cesar; Ribeiro, Rafael Antunes; Ribeiro, Clyffe de Assis; Dieguez, Pedro Ruas
2012-01-01
We present a simple and pedagogical derivation of the quantum adiabatic theorem for two-level systems (a single qubit) based on geometrical structures of quantum mechanics developed by Anandan and Aharonov, among others. We have chosen to use only the minimum geometric structure needed for the understanding of the adiabatic theorem for this case.…
The effects of ionization potential depression on the spectra emitted by hot dense aluminium plasmas
NASA Astrophysics Data System (ADS)
Preston, Thomas R.; Vinko, Sam M.; Ciricosta, Orlando; Chung, Hyun-Kyung; Lee, Richard W.; Wark, Justin S.
2013-06-01
Recent experiments at the Linac Coherent Light Source (LCLS) X-ray Free-Electron-Laser (FEL) have demonstrated that the standard model used for simulating ionization potential depression (IPD) in a plasma (the Stewart-Pyatt (SP) model, J.C. Stewart and K.D. Pyatt Jr., Astrophysical Journal 144 (1966) 1203) considerably underestimates the degree of IPD in a solid density aluminium plasma at temperatures up to 200 eV. In contrast, good agreement with the experimental data was found by use of a modified Ecker-Kröll (mEK) model (G. Ecker and W. Kröll, Physics of Fluids 6 (1963) 62-69). We present here detailed simulations, using the FLYCHK code, of the predicted spectra from hot dense, hydrogenic and helium-like aluminium plasmas ranging in densities from 0.1 to 4 times solid density, and at temperatures up to 1000 eV. Importantly, we find that the greater IPDs predicted by the mEK model result in the loss of the n = 3 states for the hydrogenic ions for all densities above ≈0.8 times solid density, and for the helium-like ions above ≈0.65 solid density. Therefore, we posit that if the mEK model holds at these higher temperatures, the temperature of solid density highly-charged aluminium plasmas cannot be determined by using spectral features associated with the n = 3 principal quantum number, and propose a re-evaluation of previous experimental data where high densities have been inferred from the spectra, and the SP model has been used.
No first ionization potential fractionation in the active stars AR Piscium and AY Ceti
NASA Astrophysics Data System (ADS)
Sanz-Forcada, J.; Affer, L.; Micela, G.
2009-10-01
Context: The comparison of coronal and photospheric abundances in cool stars is an essential question to resolve. In the Sun an enhancement of the elements with low first ionization potential (FIP) is observed in the corona with respect to the photosphere. Stars with high levels of activity seem to show a depletion of elements with low FIP when compared to solar standard values; however, the few cases of active stars in which photospheric values are available for comparison lead to confusing results, and an enlargement of the sample is mandatory for solving this longstanding problem. Aims: We calculate in this paper the photospheric and coronal abundances of two well known active binary systems, AR Psc and AY Cet, to get further insight into the complications of coronal abundances. Methods: Coronal abundances of 9 elements were calculated by means of the reconstruction of a detailed emission measure distribution, using a line-based method that considers the lines from different elements separately. Photospheric abundances of 8 elements were calculated using high-resolution optical spectra of the stars. Results: The results once again show a lack of any FIP-related effect in the coronal abundances of the stars. The presence of metal abundance depletion (MAD) or inverse FIP effects in some stars could stem from a mistaken comparison to solar photospheric values or from a deficient calculation of photospheric abundances in fast-rotating stars. Conclusions: The lack of FIP fractionation seems to confirm that Alfvén waves combined with pondermotive forces are dominant in the corona of active stars. Tables 2 and 3 are only available in electronic form at http://www.aanda.org
NASA Astrophysics Data System (ADS)
Kłos, Jacek; Alexander, Millard H.; Kumar, Praveen; Poirier, Bill; Jiang, Bin; Guo, Hua
2016-05-01
We report new and more accurate adiabatic potential energy surfaces (PESs) for the ground X˜ 1A1 and electronically excited C˜ 1B2(21A') states of the SO2 molecule. Ab initio points are calculated using the explicitly correlated internally contracted multi-reference configuration interaction (icMRCI-F12) method. A second less accurate PES for the ground X ˜ state is also calculated using an explicitly correlated single-reference coupled-cluster method with single, double, and non-iterative triple excitations [CCSD(T)-F12]. With these new three-dimensional PESs, we determine energies of the vibrational bound states and compare these values to existing literature data and experiment.
Yu Daren; Song Maojiang; Liu Hui; Zhang Xu; Li Hong
2012-07-15
Similar to a single stage Hall thruster, the magnetic field, which controls electron trajectory and electric field distribution, is the most important factor determining the performance of a double stage Hall thruster. Especially, a potential well, which is helpful to reduce the ion loss on the thruster walls, is shaped in the ionization stage due to the existence of an annular magnetic field topology there. In this paper, the influence of magnetic field strength in the ionization stage on the potential well is researched with both experiments and particle-in-cell simulations. It is found that the depth of potential well increases with the magnetic field strength as a result of enhanced magnetic confinement and lowered electron conductivity. Consequently, the plasma density as well as the ion current entering the acceleration stage increases. However, an excessive magnetic field strength leads to an excess of ion loss on the walls of the acceleration stage. Therefore, there is an appropriate magnetic field strength in the ionization stage that results in a proper potential well and consequently an optimal performance of a double stage Hall thruster.
NASA Astrophysics Data System (ADS)
Verma, Prakash; Bartlett, Rodney J.
2016-07-01
Core excitation energies are computed with time-dependent density functional theory (TD-DFT) using the ionization energy corrected exchange and correlation potential QTP(0,0). QTP(0,0) provides C, N, and O K-edge spectra to about an electron volt. A mean absolute error (MAE) of 0.77 and a maximum error of 2.6 eV is observed for QTP(0,0) for many small molecules. TD-DFT based on QTP (0,0) is then used to describe the core-excitation spectra of the 22 amino acids. TD-DFT with conventional functionals greatly underestimates core excitation energies, largely due to the significant error in the Kohn-Sham occupied eigenvalues. To the contrary, the ionization energy corrected potential, QTP(0,0), provides excellent approximations (MAE of 0.53 eV) for core ionization energies as eigenvalues of the Kohn-Sham equations. As a consequence, core excitation energies are accurately described with QTP(0,0), as are the core ionization energies important in X-ray photoionization spectra or electron spectroscopy for chemical analysis.
Verma, Prakash; Bartlett, Rodney J
2016-07-21
Core excitation energies are computed with time-dependent density functional theory (TD-DFT) using the ionization energy corrected exchange and correlation potential QTP(0,0). QTP(0,0) provides C, N, and O K-edge spectra to about an electron volt. A mean absolute error (MAE) of 0.77 and a maximum error of 2.6 eV is observed for QTP(0,0) for many small molecules. TD-DFT based on QTP (0,0) is then used to describe the core-excitation spectra of the 22 amino acids. TD-DFT with conventional functionals greatly underestimates core excitation energies, largely due to the significant error in the Kohn-Sham occupied eigenvalues. To the contrary, the ionization energy corrected potential, QTP(0,0), provides excellent approximations (MAE of 0.53 eV) for core ionization energies as eigenvalues of the Kohn-Sham equations. As a consequence, core excitation energies are accurately described with QTP(0,0), as are the core ionization energies important in X-ray photoionization spectra or electron spectroscopy for chemical analysis. PMID:27448875
HF echoes from ionization potentially produced by high-altitude discharges
Roussel-Dupre, R.A.; Blanc, E.
1997-03-01
The presence of ionization associated with high-altitude discharges has been detected using an HF radar operating at 2.2, 2.5, and 2.8 MHz. On several occasions, oblique echoes lasting several hundred ms at night and 1{r_arrow}10s during the day were observed. The echoes turned on in several interpulse times of 70 ms and were generally correlated with strong lightning activity prior to onset. The angles of arrival of sferics detected at three goniometer stations were used to determine the distance to thunderstorms. The data are consistent with specular reflections from columns of ionization produced at 55{endash}65 km altitude and having minimum electron densities of 6{times}10{sup 4}{endash}10{sup 5}cm{sup {minus}3}. The source of the ionization is believed to be high-altitude discharges.{copyright} 1997 American Geophysical Union
Falcinelli, Stefano; Rosi, Marzio; Pirani, Fernando; Stranges, Domenico; Vecchiocattivi, Franco
2016-07-14
In this work, we present and analyze in detail new and recent ionization cross section and mass spectrum determinations, collected in the case of He*, Ne*-H2O, -H2S, and -NH3 ionizing collisions. These sets of data, obtained under the same experimental conditions, are relevant to identify differences in the autoionization stereodynamics of the three hydrogenated molecules and on the selective role of the imaginary part of the optical potential. We demonstrate that in these autoionization processes hydrogen and halogen bonds are competing because they are controlling both real and imaginary components of the optical potential that drives the complete reaction dynamics. In particular, we found that both components critically depend on the angular and radial approach between the reagent partners in determining the collision dynamics. PMID:26938026
Krause, Pascal; Schlegel, H. Bernhard
2014-11-07
The strong field ionization rates for ethylene, trans 1,3-butadiene, and trans,trans 1,3,5-hexatriene have been calculated using time-dependent configuration interaction with single excitations and a complex absorbing potential (TDCIS-CAP). The calculations used the aug-cc-pVTZ basis set with a large set of diffuse functions (3 s, 2 p, 3 d, and 1 f) on each atom. The absorbing boundary was placed 3.5 times the van der Waals radius from each atom. The simulations employed a seven-cycle cosine squared pulse with a wavelength of 800 nm. Ionization rates were calculated for intensities ranging from 0.3 × 10{sup 14} W/cm{sup 2} to 3.5 × 10{sup 14} W/cm{sup 2}. Ionization rates along the molecular axis increased markedly with increasing conjugation length. By contrast, ionization rates perpendicular to the molecular axis were almost independent of the conjugation length.
Krause, Pascal; Schlegel, H Bernhard
2014-11-01
The strong field ionization rates for ethylene, trans 1,3-butadiene, and trans,trans 1,3,5-hexatriene have been calculated using time-dependent configuration interaction with single excitations and a complex absorbing potential (TDCIS-CAP). The calculations used the aug-cc-pVTZ basis set with a large set of diffuse functions (3 s, 2 p, 3 d, and 1 f) on each atom. The absorbing boundary was placed 3.5 times the van der Waals radius from each atom. The simulations employed a seven-cycle cosine squared pulse with a wavelength of 800 nm. Ionization rates were calculated for intensities ranging from 0.3 × 10(14) W/cm(2) to 3.5 × 10(14) W/cm(2). Ionization rates along the molecular axis increased markedly with increasing conjugation length. By contrast, ionization rates perpendicular to the molecular axis were almost independent of the conjugation length. PMID:25381499
Complete population inversion of Bose particles by an adiabatic cycle
NASA Astrophysics Data System (ADS)
Tanaka, Atushi; Cheon, Taksu
2016-04-01
We show that an adiabatic cycle excites Bose particles confined in a one-dimensional box. During the adiabatic cycle, a wall described by a δ-shaped potential is applied and its strength and position are slowly varied. When the system is initially prepared in the ground state, namely, in the zero-temperature equilibrium state, the adiabatic cycle brings all Bosons into the first excited one-particle state, leaving the system in a nonequilibrium state. The absorbed energy during the cycle is proportional to the number of Bosons.
Toth, A.; Nagy, L.
2011-10-03
We have carried out calculations for the fully differential cross section of the ionization of helium by electron projectiles. In order to study the effect of the residual ion potential, we employed three models, and tested them for the coplanar and perpendicular plane geometry. In spite of the simplicity of our models, the results for the coplanar case are in fair agreement with the available experimental data. The results for the perpendicular geometry need more improvement.
Golibrzuch, Kai; Shirhatti, Pranav R.; Kandratsenka, Alexander; Wodtke, Alec M.; Bartels, Christof; Max Planck Institute for Biophysical Chemistry, Göttingen 37077 ; Rahinov, Igor; Auerbach, Daniel J.; Max Planck Institute for Biophysical Chemistry, Göttingen 37077; Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106
2014-01-28
We present a combined experimental and theoretical study of NO(v = 3 → 3, 2, 1) scattering from a Au(111) surface at incidence translational energies ranging from 0.1 to 1.2 eV. Experimentally, molecular beam–surface scattering is combined with vibrational overtone pumping and quantum-state selective detection of the recoiling molecules. Theoretically, we employ a recently developed first-principles approach, which employs an Independent Electron Surface Hopping (IESH) algorithm to model the nonadiabatic dynamics on a Newns-Anderson Hamiltonian derived from density functional theory. This approach has been successful when compared to previously reported NO/Au scattering data. The experiments presented here show that vibrational relaxation probabilities increase with incidence energy of translation. The theoretical simulations incorrectly predict high relaxation probabilities at low incidence translational energy. We show that this behavior originates from trajectories exhibiting multiple bounces at the surface, associated with deeper penetration and favored (N-down) molecular orientation, resulting in a higher average number of electronic hops and thus stronger vibrational relaxation. The experimentally observed narrow angular distributions suggest that mainly single-bounce collisions are important. Restricting the simulations by selecting only single-bounce trajectories improves agreement with experiment. The multiple bounce artifacts discovered in this work are also present in simulations employing electronic friction and even for electronically adiabatic simulations, meaning they are not a direct result of the IESH algorithm. This work demonstrates how even subtle errors in the adiabatic interaction potential, especially those that influence the interaction time of the molecule with the surface, can lead to an incorrect description of electronically nonadiabatic vibrational energy transfer in molecule-surface collisions.
Adiabatic theory for anisotropic cold molecule collisions
Pawlak, Mariusz; Shagam, Yuval; Narevicius, Edvardas; Moiseyev, Nimrod
2015-08-21
We developed an adiabatic theory for cold anisotropic collisions between slow atoms and cold molecules. It enables us to investigate the importance of the couplings between the projection states of the rotational motion of the atom about the molecular axis of the diatom. We tested our theory using the recent results from the Penning ionization reaction experiment {sup 4}He(1s2s {sup 3}S) + HD(1s{sup 2}) → {sup 4}He(1s{sup 2}) + HD{sup +}(1s) + e{sup −} [Lavert-Ofir et al., Nat. Chem. 6, 332 (2014)] and demonstrated that the couplings have strong effect on positions of shape resonances. The theory we derived provides cross sections which are in a very good agreement with the experimental findings.
Adiabatic theory for anisotropic cold molecule collisions.
Pawlak, Mariusz; Shagam, Yuval; Narevicius, Edvardas; Moiseyev, Nimrod
2015-08-21
We developed an adiabatic theory for cold anisotropic collisions between slow atoms and cold molecules. It enables us to investigate the importance of the couplings between the projection states of the rotational motion of the atom about the molecular axis of the diatom. We tested our theory using the recent results from the Penning ionization reaction experiment (4)He(1s2s (3)S) + HD(1s(2)) → (4)He(1s(2)) + HD(+)(1s) + e(-) [Lavert-Ofir et al., Nat. Chem. 6, 332 (2014)] and demonstrated that the couplings have strong effect on positions of shape resonances. The theory we derived provides cross sections which are in a very good agreement with the experimental findings. PMID:26298122
Multisurface Adiabatic Reactive Molecular Dynamics.
Nagy, Tibor; Yosa Reyes, Juvenal; Meuwly, Markus
2014-04-01
Adiabatic reactive molecular dynamics (ARMD) simulation method is a surface-crossing algorithm for modeling chemical reactions in classical molecular dynamics simulations using empirical force fields. As the ARMD Hamiltonian is time dependent during crossing, it allows only approximate energy conservation. In the current work, the range of applicability of conventional ARMD is explored, and a new multisurface ARMD (MS-ARMD) method is presented, implemented in CHARMM and applied to the vibrationally induced photodissociation of sulfuric acid (H2SO4) in the gas phase. For this, an accurate global potential energy surface (PES) involving 12 H2SO4 and 4 H2O + SO3 force fields fitted to MP2/6-311G++(2d,2p) reference energies is employed. The MS-ARMD simulations conserve total energy and feature both intramolecular H-transfer reactions and water elimination. An analytical treatment of the dynamics in the crossing region finds that conventional ARMD can approximately conserve total energy for limiting cases. In one of them, the reduced mass of the system is large, which often occurs for simulations of solvated biomolecular systems. On the other hand, MS-ARMD is a general approach for modeling chemical reactions including gas-phase, homogeneous, heterogeneous, and enzymatic catalytic reactions while conserving total energy in atomistic simulations. PMID:26580356
Acceleration of adiabatic quantum dynamics in electromagnetic fields
Masuda, Shumpei; Nakamura, Katsuhiro
2011-10-15
We show a method to accelerate quantum adiabatic dynamics of wave functions under electromagnetic field (EMF) by developing the preceding theory [Masuda and Nakamura, Proc. R. Soc. London Ser. A 466, 1135 (2010)]. Treating the orbital dynamics of a charged particle in EMF, we derive the driving field which accelerates quantum adiabatic dynamics in order to obtain the final adiabatic states in any desired short time. The scheme is consolidated by describing a way to overcome possible singularities in both the additional phase and driving potential due to nodes proper to wave functions under EMF. As explicit examples, we exhibit the fast forward of adiabatic squeezing and transport of excited Landau states with nonzero angular momentum, obtaining the result consistent with the transitionless quantum driving applied to the orbital dynamics in EMF.
Adiabatic and isocurvature perturbation projections in multi-field inflation
NASA Astrophysics Data System (ADS)
Gordon, Chris; Saffin, Paul M.
2013-08-01
Current data are in good agreement with the predictions of single field inflation. However, the hemispherical asymmetry, seen in the cosmic microwave background data, may hint at a potential problem. Generalizing to multi-field models may provide one possible explanation. A useful way of modeling perturbations in multi-field inflation is to investigate the projection of the perturbation along and perpendicular to the background fields' trajectory. These correspond to the adiabatic and isocurvature perturbations. However, it is important to note that in general there are no corresponding adiabatic and isocurvature fields. The purpose of this article is to highlight the distinction between a field redefinition and a perturbation projection. We provide a detailed derivation of the evolution of the isocurvature perturbation to show that no assumption of an adiabatic or isocurvature field is needed. We also show how this evolution equation is consistent with the field covariant evolution equations for the adiabatic perturbation in the flat field space limit.
Quantum Monte Carlo simulations of tunneling in quantum adiabatic optimization
NASA Astrophysics Data System (ADS)
Brady, Lucas T.; van Dam, Wim
2016-03-01
We explore to what extent path-integral quantum Monte Carlo methods can efficiently simulate quantum adiabatic optimization algorithms during a quantum tunneling process. Specifically we look at symmetric cost functions defined over n bits with a single potential barrier that a successful quantum adiabatic optimization algorithm will have to tunnel through. The height and width of this barrier depend on n , and by tuning these dependencies, we can make the optimization algorithm succeed or fail in polynomial time. In this article we compare the strength of quantum adiabatic tunneling with that of path-integral quantum Monte Carlo methods. We find numerical evidence that quantum Monte Carlo algorithms will succeed in the same regimes where quantum adiabatic optimization succeeds.
Microwave ionization of Rydberg atoms
Gallagher, T.F.
1996-12-31
An atom can be ionized by a static field if the field depresses the potential below the binding energy W, leading to the requirement E = W{sup 2}/4 in atomic units. The atomic units of field and energy are 5.14 {times} 10{sup 9} V/cm and 27.2 eV. The ionization field is often expressed in terms of the principal quantum number n of the state in question as E = 1/16n{sup 4}. In a microwave field with frequency far less than the separation {Delta}W = 1/n{sup 3} between adjacent n states, atoms other than H ionize at the much lower microwave field amplitude of E = 1/3n{sup 5}. This field corresponds to the Inglis-Teller limit, where it is impossible to resolve spectrally adjacent n states due to Stark broadening in a plasma. In H ionization occurs as it does in a static field. The difference exists because the finite sized ionic core of a non hydrogenic atom breaks one of the symmetries found in H. In non hydrogenic atoms the microwave field drives a series of transitions through successively higher n states culminating in ionization. These transitions can be understood in terms of a Landau-Zener picture based on the variation of the energies of the atoms produced by the time varying field or as the resonant multiphoton absorption of the microwave photons. In either case, the atoms make transitions through real intermediate states en route to ionization. With short, four cycle, microwave pulses complete ionization does not occur with fields of E = 1/3n{sup 5}, and population is left in intermediate states. The transition from ionization at fields near E = 1/3n{sup 5} to fields of E = 1/16n{sup 4} occurs when the frequency becomes low enough that the energies of the states vary adiabatically in the temporally varying field.
NASA Astrophysics Data System (ADS)
Li, Yong-Qing; Song, Yu-Zhi; Joaquim de Campos Varandas, António
2015-01-01
An accurate single-sheeted double many-body expansion potential energy surface is reported for the title system. It is obtained by using the aug-cc-pVTZ and aug-cc-pVQZ basis sets with extrapolation of the electron correlation energy to the complete basis set limit, plus extrapolation to the complete basis set limit of the complete-active-space self-consistent field energy. The collinear and bending barrier heights of the new global potential energy surface is 2.301 and 1.768 kcal mol-1, in very good agreement with the values of 2.222 and 1.770 kcal mol-1 from the current best potential energy surface. In particular, the new potential energy surface describes well the important van der Waals interactions which is very useful for investigating the dynamics of the title system. Thus, the new potential energy surface can both be recommended for dynamics studies of the F + H2 reaction and as building block for constructing the potential energy surfaces of larger fluorine/hydrogen containing systems. Based on the new potential energy surface, a preliminary theoretical study of the reaction F(2P) + H2 (X1 Σg+) → FH(X1Σ+) + H(2S) has been carried out with the methods of quasi-classical trajectory and quantum mechanical. The results have shown that the new PES is suitable for any kind of dynamics studies. Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2014-50445-3
Bernstein, N. K.; Karimi-Busheri, F.; Rasouli-Nia, A.; Mani, R.; Dianov, G.; Glover, J. N. M.; Weinfeld, M.
2010-01-01
The cytotoxicity of many antineoplastic agents is due to their capacity to damage DNA and there is evidence indicating that DNA repair contributes to the cellular resistance to such agents. DNA strand breaks constitute a significant proportion of the lesions generated by a broad range of genotoxic agents, either directly, or during the course of DNA repair. Strand breaks that are caused by many agents including ionizing radiation, topoisomerase I inhibitors, and DNA repair glycosylases such as NEIL1 and NEIL2, often contain 5’-hydroxyl and/or 3’-phosphate termini. These ends must be converted to 5’-phosphate and 3’-hydroxyl termini in order to allow DNA polymerases and ligases to catalyze repair synthesis and strand rejoining. A key enzyme involved in this end-processing is polynucleotide kinase (PNK), which possesses two enzyme activities, a DNA 5’-kinase activity and a 3’-phosphatase activity. PNK participates in the single-strand break repair pathway and the non-homologous end joining pathway for double-strand break repair. RNAi-mediated down-regulation of PNK renders cells more sensitive to ionizing radiation and camptothecin, a topoisomerase I inhibitor. Structural analysis of PNK revealed the protein is composed of three domains, the kinase domain at the C-terminus, the phosphatase domain in the centre and a forkhead associated (FHA) domain at the N-terminus. The FHA domain plays a critical role in the binding of PNK to other DNA repair proteins. Thus each PNK domain may be a suitable target for small molecule inhibition to effectively reduce resistance to ionizing radiation and topoisomerase I inhibitors. PMID:18473721
Neutral resonant ionization in a H- plasma source: Potential of doubly excited **H-
NASA Astrophysics Data System (ADS)
Vogel, J. S.
2016-02-01
Hydrogen plasmas are optically dense to Lyman-α radiation, maintaining *H(n = 2) neutral atoms that may undergo neutral resonant ionization to **H-. One state, **H-(2p2 3Pe), is thought bound at 9.7 meV with a several nanosecond lifetime while all others are unbound resonances. Collision dynamics of two *H(2s) shows that an ionic pair of (p, **H-) resolves at least three long-standing collision experiments. The doubly excited anion also has a path to the unexcited ion pair whose only physical distinction is that both (p, H-) have energy of 3.7 eV.
Tupitsyn, I.I.
1988-03-01
The ionization potentials of the halogen group have been calculated. The calculations were carried out using the relativistic Hartree-Fock method taking into account correlation effects. Comparison of theoretical results with experimental data for the elements F, Cl, Br, and I allows an estimation of the accuracy and reliability of the method. The theoretical values of the ionization potential of astatine obtained here may be of definite interest for the chemistry of astatine.
Bhaskaran-Nair, Kiran; Kowalski, Karol; Moreno, Juana; Jarrell, Mark; Shelton, William A.
2014-08-21
Discovery of fullerenes has opened a entirely new chapter in chemistry due to their wide range of properties which holds exciting applications in numerous disciplines of science. The Nobel Prize in Chemistry 1996 was awarded jointly to Robert F. Curl Jr., Sir Harold W. Kroto and Richard E. Smalley in recoginition for their discovery of this new carbon allotrope. In this letter we are reporting ionization potential and electron attachment studies on fullerenes (C60 and C70) obtained with novel parallel implementation of the EA-EOM-CCSD and IP-EOM-CCSD methods in NWChem program package.
Chang, Zhiwei; Li, Jiguang; Dong, Chenzhong
2010-12-30
Multiconfiguration Dirac-Fock (MCDF) method was employed to calculate the first five ionization potentials, electron affinities, resonance excitation energies, oscillator strengths, and radii for the element Uus and its homologue At. Main valence correlation effects were taken into account. The Breit interaction and QED effects were also estimated. The uncertainties of calculated IPs, EAs, and IR for Uus and At were reduced through an extrapolation procedure. The good consistency with available experimental and other theoretical values demonstrates the validity of the present results. These theoretical data therefore can be used to predict some unknown physicochemical properties of element Uus, Astatine, and their compounds. PMID:21141866
Kuś, Tomasz; Krylov, Anna I
2011-08-28
The charge-stabilization method is applied to double ionization potential equation-of-motion (EOM-DIP) calculations to stabilize unstable dianion reference functions. The auto-ionizing character of the dianionic reference states spoils the numeric performance of EOM-DIP limiting applications of this method. We demonstrate that reliable excitation energies can be computed by EOM-DIP using a stabilized resonance wave function instead of the lowest energy solution corresponding to the neutral + free electron(s) state of the system. The details of charge-stabilization procedure are discussed and illustrated by examples. The choice of optimal stabilizing Coulomb potential, which is strong enough to stabilize the dianion reference, yet, minimally perturbs the target states of the neutral, is the crux of the approach. Two algorithms of choosing optimal parameters of the stabilization potential are presented. One is based on the orbital energies, and another--on the basis set dependence of the total Hartree-Fock energy of the reference. Our benchmark calculations of the singlet-triplet energy gaps in several diradicals show a remarkable improvement of the EOM-DIP accuracy in problematic cases. Overall, the excitation energies in diradicals computed using the stabilized EOM-DIP are within 0.2 eV from the reference EOM spin-flip values. PMID:21895161
Inertial effects in adiabatically driven flashing ratchets
NASA Astrophysics Data System (ADS)
Rozenbaum, Viktor M.; Makhnovskii, Yurii A.; Shapochkina, Irina V.; Sheu, Sheh-Yi; Yang, Dah-Yen; Lin, Sheng Hsien
2014-05-01
We study analytically the effect of a small inertial correction on the properties of adiabatically driven flashing ratchets. Parrondo's lemma [J. M. R. Parrondo, Phys. Rev. E 57, 7297 (1998), 10.1103/PhysRevE.57.7297] is generalized to include the inertial term so as to establish the symmetry conditions allowing directed motion (other than in the overdamped massless case) and to obtain a high-temperature expansion of the motion velocity for arbitrary potential profiles. The inertial correction is thus shown to enhance the ratchet effect at all temperatures for sawtooth potentials and at high temperatures for simple potentials described by the first two harmonics. With the special choice of potentials represented by at least the first three harmonics, the correction gives rise to the motion reversal in the high-temperature region. In the low-temperature region, inertia weakens the ratchet effect, with the exception of the on-off model, where diffusion is important. The directed motion adiabatically driven by potential sign fluctuations, though forbidden in the overdamped limit, becomes possible due to purely inertial effects in neither symmetric nor antisymmetric potentials, i.e., not for commonly used sawtooth and two-sinusoid profiles.
Li, Y Q; Ma, F C; Sun, M T
2013-10-21
A full three-dimensional global potential energy surface is reported first time for the title system, which is important for the photodissociation processes. It is obtained using double many-body expansion theory and an extensive set of accurate ab initio energies extrapolated to the complete basis set limit. Such a work can be recommended for dynamics studies of the N((2)D) + H2 reaction, a reliable theoretical treatment of the photodissociation dynamics and as building blocks for constructing the double many-body expansion potential energy surface of larger nitrogen/hydrogen containing systems. In turn, a preliminary theoretical study of the reaction N((2)D)+H2(X(1)Σg (+))(ν=0,j=0)→NH(a(1)Δ)+H((2)S) has been carried out with the method of quasi-classical trajectory on the new potential energy surface. Integral cross sections and thermal rate constants have been calculated, providing perhaps the most reliable estimate of the integral cross sections and the rate constants known thus far for such a reaction. PMID:24160511
NASA Astrophysics Data System (ADS)
Li, Y. Q.; Ma, F. C.; Sun, M. T.
2013-10-01
A full three-dimensional global potential energy surface is reported first time for the title system, which is important for the photodissociation processes. It is obtained using double many-body expansion theory and an extensive set of accurate ab initio energies extrapolated to the complete basis set limit. Such a work can be recommended for dynamics studies of the N(2D) + H2 reaction, a reliable theoretical treatment of the photodissociation dynamics and as building blocks for constructing the double many-body expansion potential energy surface of larger nitrogen/hydrogen containing systems. In turn, a preliminary theoretical study of the reaction N(^2D)+H_2(X^1Σ _g^+)(ν =0,j=0)rArr NH(a^1Δ )+H(^2S) has been carried out with the method of quasi-classical trajectory on the new potential energy surface. Integral cross sections and thermal rate constants have been calculated, providing perhaps the most reliable estimate of the integral cross sections and the rate constants known thus far for such a reaction.
Momot, A. I.; M.M. Bogolubov Institute for Theoretical Physics, Nat. Acad. Sci. of Ukraine, 14b, Metrologichna Str., Kyiv, 03680
2013-07-15
The problem of grain screening is solved numerically for the case of weakly ionized plasma in the presence of an external magnetic field. The plasma dynamics is described within the drift-diffusion approximation under the assumption that the grain absorbs all encountered electrons and ions. We also assume that the plasma current through the grain surface is equal to zero in the stationary state. This condition is used to perform self-consistent calculations of the grain charge. The spatial distribution of the screened grain potential is studied and compared with the analytical estimates. It is shown that at the distances larger than the Debye length such potential has the Coulomb-like asymptotics with the effective charge dependent on the angle between the radius vector and the external magnetic field direction. The numerical solutions show that in the direction parallel to the external magnetic field the effective potential can have nonmonotonic behavior.
NASA Astrophysics Data System (ADS)
Chan, Y. C.; Harding, D. R.; Stwalley, W. C.; Vidal, C. R.
1986-09-01
Laser-induced fluorescence (LIF) spectra of the A-X system of the LiH isotopes, excited by the UV lines of an argon and a krypton ion laser, were observed and analyzed. Three long LIF series of different LiH isotopes were taken with a 3.4 m high resolution spectrograph. The results were combined with previous experimental data to study the breakdown of the Born-Oppenheimer approximation in the X 1Σ+ electronic ground state of the isotopic LiH molecules. Using a quantum mechanical variational method, potential energy curves of the four LiH isotopes were extended almost up to the dissociation limits.
Theory of warm ionized gases: equation of state and kinetic Schottky anomaly.
Capolupo, A; Giampaolo, S M; Illuminati, F
2013-10-01
Based on accurate Lennard-Jones-type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analog in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed. In particular, the predicted plasma electron density in a sonoluminescent bubble turns out to be in good agreement with the value measured in recent experiments. PMID:24229140
Mielke, Steven L; Schwenke, David W; Schatz, George C; Garrett, Bruce C; Peterson, Kirk A
2009-04-23
Multireference configuration interaction (MRCI) calculations of the Born-Oppenheimer diagonal correction (BODC) for H(3) were performed at 1397 symmetry-unique configurations using the Handy-Yamaguchi-Schaefer approach; isotopic substitution leads to 4041 symmetry-unique configurations for the DH(2) mass combination. These results were then fit to a functional form that permits calculation of the BODC for any combination of isotopes. Mean unsigned fitting errors on a test grid of configurations not included in the fitting process were 0.14, 0.12, and 0.65 cm(-1) for the H(3), DH(2), and MuH(2) isotopomers, respectively. This representation can be combined with any Born-Oppenheimer potential energy surface (PES) to yield Born-Huang (BH) PESs; herein, we choose the CCI potential energy surface, the uncertainties of which ( approximately 0.01 kcal/mol) are much smaller than the magnitude of the BODC. Fortran routines to evaluate these BH surfaces are provided. Variational transition state theory calculations are presented comparing thermal rate constants for reactions on the BO and BH surfaces to provide an initial estimate of the significance of the diagonal correction for the dynamics. PMID:19290604
Revisiting The Brightest RV Tauri Star: First Ionization Potential (FIP) Effect in R Sct
NASA Astrophysics Data System (ADS)
Yolalan, Gizay; Sahin, Timur
2016-07-01
We have derived elemental abundances of the brightest RV Tauri star, R Sct. The abundance analysis of the star is based on high resolution and high quality (S/N>300) echelle spectra, mainly obtained for radial velocity study of a large sample of IRAS like RV Tau sample stars, from the McDonald Observatory (R~48,000). Our analysis is based on optical spectra obtained at only one phase of the variation. The standard 1D LTE analysis provided a fresh determination of the atmospheric parameters: Teff=5000 K, logg=1.05 cgs, and a microturbulence velocity ξ=3.4 km/s and [Fe/H] = -0.33. We report on chemical abundances of 10 neutral and ionized species identified over 4800 - 5600 A wavelength region. In an effort to explain observed deficiency in abundances, possible scenarios including FIP is investigated.
Adiabatic evolution of plasma equilibrium
Grad, H.; Hu, P. N.; Stevens, D. C.
1975-01-01
A new theory of plasma equilibrium is introduced in which adiabatic constraints are specified. This leads to a mathematically nonstandard structure, as compared to the usual equilibrium theory, in which prescription of pressure and current profiles leads to an elliptic partial differential equation. Topologically complex configurations require further generalization of the concept of adiabaticity to allow irreversible mixing of plasma and magnetic flux among islands. Matching conditions across a boundary layer at the separatrix are obtained from appropriate conservation laws. Applications are made to configurations with planned islands (as in Doublet) and accidental islands (as in Tokamaks). Two-dimensional, axially symmetric, helically symmetric, and closed line equilibria are included. PMID:16578729
Crystal, J.; Friesner, R.A.
2000-03-23
Ionization potentials (IP) and electron affinities (EA) are calculated for bacteriopheophytin (BPh) and bacteriochlorophyll (BChl) in the photosynthetic reaction center utilizing density functional methods implemented in a parallel version of the JAGUAR electronic structure code. These quantities are studied as a function of basis set size and molecular geometry. The results indicate the necessity of using large basis sets with diffuse functions in order to obtain reliable IP and EA in the gas phase. The relative reduction potentials of BChl and BPh in dimethylformamide solution are also calculated and compared with experimental results. Excellent agreement between theory and experiment is obtained when ligand binding of solvent molecules to the central Mg atom of BNhl is incorporated in the calculations.
Shortcuts to adiabaticity in a time-dependent box
Campo, A. del; Boshier, M. G.
2012-01-01
A method is proposed to drive an ultrafast non-adiabatic dynamics of an ultracold gas trapped in a time-dependent box potential. The resulting state is free from spurious excitations associated with the breakdown of adiabaticity, and preserves the quantum correlations of the initial state up to a scaling factor. The process relies on the existence of an adiabatic invariant and the inversion of the dynamical self-similar scaling law dictated by it. Its physical implementation generally requires the use of an auxiliary expulsive potential. The method is extended to a broad family of interacting many-body systems. As illustrative examples we consider the ultrafast expansion of a Tonks-Girardeau gas and of Bose-Einstein condensates in different dimensions, where the method exhibits an excellent robustness against different regimes of interactions and the features of an experimentally realizable box potential. PMID:22970340
Experimental breaking of an adiabatic invariant
NASA Astrophysics Data System (ADS)
Notte, J.; Fajans, J.; Chu, R.; Wurtele, J. S.
1993-06-01
When a cylindrical pure electron plasma is displaced from the center of the trap, it performs a bulk circular orbital motion known as the l=1 diocotron mode. The slow application of a perturbing potential to a patch on the trap wall distorts the orbit into a noncircular closed path. Experiments and a simple theoretical model indicate that the area by the loop is an adiabatic invariant. Detailed studies are made of the breaking of the invariant when perturbations are rapidly applied. When the perturbation is applied with discontinuous time derivatives, the invariant breaking greatly exceeds the predictions of the standard theory for smooth perturbations.
[Bond selective chemistry beyond the adiabatic approximation
Butler, L.J.
1993-02-28
The adiabatic Born-Oppenheimer potential energy surface approximation is not valid for reaction of a wide variety of energetic materials and organic fuels; coupling between electronic states of reacting species plays a key role in determining the selectivity of the chemical reactions induced. This research program initially studies this coupling in (1) selective C-Br bond fission in 1,3- bromoiodopropane, (2) C-S:S-H bond fission branching in CH[sub 3]SH, and (3) competition between bond fission channels and H[sub 2] elimination in CH[sub 3]NH[sub 2].
Local entanglement generation in the adiabatic regime
Cliche, M.; Veitia, Andrzej
2010-09-15
We study entanglement generation in a pair of qubits interacting with an initially correlated system. Using time-independent perturbation theory and the adiabatic theorem, we show conditions under which the qubits become entangled as the joint system evolves into the ground state of the interacting theory. We then apply these results to the case of qubits interacting with a scalar quantum field. We study three different variations of this setup; a quantum field subject to Dirichlet boundary conditions, a quantum field interacting with a classical potential, and a quantum field that starts in a thermal state.
Millis, C D; Cai, D Y; Stankovich, M T; Tien, M
1989-10-17
The oxidation-reduction potentials of lignin peroxidase isozymes H1, H2, H8, and H10 as well as the Mn-dependent peroxidase isozymes H3 and H4 are reported. The potentiometric titrations involving the ferrous and ferric states of the enzyme had Nernst plots indicating single-electron transfer. The Em7 values of lignin peroxidase isozymes H1, H2, H8, and H10 are -142, -135, -137, and -127 mV versus standard hydrogen electrode, respectively. The Em7 values for the Mn-dependent peroxidase isozymes H3 and H4 are -88 and -93 mV versus standard hydrogen electrode, respectively. The midpoint potential of H1, H8, and H4 remained unchanged in the presence of their respective substrates, veratryl alcohol and Mn(II). The midpoint potential between the ferric and ferrous forms of isozymes H1 and H4 exhibited a pH-dependent change between pH 3.5 and pH 6.5. These results indicate that the reductive half-reaction of the enzymes is the following: ferric peroxidase + le- + H+----ferrous peroxidase. Above pH 6.5, the effect of pH on the midpoint potential is diminished and indicates that an ionization with an apparent pKa equal to approximately 6.6-6.7 occurs in the reduced form of the enzymes. A heme-linked ionization group in the ferrous form of the enzymes was confirmed by studying the effect of pH on the absorption spectra of isozymes H1 and H4. These spectrophotometric pH titration experiments confirmed the electrochemical results indicating pKa values of 6.59 and 6.69 for reduced isozymes H1 and H4, respectively. These results indicate the presence of a heme-linked ionization of an amino acid in the reduced form of the lignin peroxidase isozymes similar to that of other plant peroxidases. PMID:2605198
Sanders, Charles L
2012-12-01
Ultra-low doses and dose- rates of ionizing radiation are effective in preventing disease which suggests that they also may be effective in treating disease. Limited experimental and anecdotal evidence indicates that low radiation doses from radon in mines and spas, thorium-bearing monazite sands and enhanced radioactive uranium ore obtained from a natural geological reactor may be useful in treating many inflammatory conditions and proliferative disorders, including cancer. Optimal therapeutic applications were identified via a literature survey as dose-rates ranging from 7 to 11μGy/hr or 28 to 44 times world average background rates. Rocks from an abandoned uranium mine in Utah were considered for therapeutic application and were examined by γ-ray and laser-induced breakdown fluorescence spectroscopy. The rocks showed the presence of transuranics and fission products with a γ-ray energy profile similar to aged spent uranium nuclear fuel (93% dose due to β particles and 7% due to γ rays). Mud packs of pulverized uranium ore rock dust in sealed plastic bags delivering bag surface β,γ dose-rates of 10-450 μGy/h were used with apparent success to treat several inflammatory and proliferative conditions in humans. PMID:23304108
Sanders, Charles L.
2012-01-01
Ultra-low doses and dose- rates of ionizing radiation are effective in preventing disease which suggests that they also may be effective in treating disease. Limited experimental and anecdotal evidence indicates that low radiation doses from radon in mines and spas, thorium-bearing monazite sands and enhanced radioactive uranium ore obtained from a natural geological reactor may be useful in treating many inflammatory conditions and proliferative disorders, including cancer. Optimal therapeutic applications were identified via a literature survey as dose-rates ranging from 7 to 11μGy/hr or 28 to 44 times world average background rates. Rocks from an abandoned uranium mine in Utah were considered for therapeutic application and were examined by γ-ray and laser-induced breakdown fluorescence spectroscopy. The rocks showed the presence of transuranics and fission products with a γ-ray energy profile similar to aged spent uranium nuclear fuel (93% dose due to β particles and 7% due to γ rays). Mud packs of pulverized uranium ore rock dust in sealed plastic bags delivering bag surface β,γ dose-rates of 10–450 μGy/h were used with apparent success to treat several inflammatory and proliferative conditions in humans. PMID:23304108
Pressure Oscillations in Adiabatic Compression
ERIC Educational Resources Information Center
Stout, Roland
2011-01-01
After finding Moloney and McGarvey's modified adiabatic compression apparatus, I decided to insert this experiment into my physical chemistry laboratory at the last minute, replacing a problematic experiment. With insufficient time to build the apparatus, we placed a bottle between two thick textbooks and compressed it with a third textbook forced…
Adiabatic dynamics of magnetic vortices
NASA Astrophysics Data System (ADS)
Papanicolaou, N.
1994-03-01
We formulate a reasonably detailed adiabatic conjecture concerning the dynamics of skew deflection of magnetic vortices in a field gradient, which is expected to be valid at sufficiently large values of the winding number. The conjecture is consistent with the golden rule used to describe the dynamics of realistic magnetic bubbles and is verified here numerically within the 2-D isotropic Heisenberg model.
Transitionless driving on adiabatic search algorithm
Oh, Sangchul; Kais, Sabre
2014-12-14
We study quantum dynamics of the adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolution is studied and visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for the short running time to inverse-square decay in asymptotic running time. The scaling of the critical running time is expressed in terms of the Lambert W function. We derive the transitionless driving Hamiltonian for the adiabatic search algorithm, which makes a quantum state follow the adiabatic path. We demonstrate that a uniform transitionless driving Hamiltonian, approximate to the exact time-dependent driving Hamiltonian, can alter the non-adiabatic transition probability from the inverse square decay to the inverse fourth power decay with the running time. This may open up a new but simple way of speeding up adiabatic quantum dynamics.
Transitionless driving on adiabatic search algorithm
NASA Astrophysics Data System (ADS)
Oh, Sangchul; Kais, Sabre
2014-12-01
We study quantum dynamics of the adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolution is studied and visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for the short running time to inverse-square decay in asymptotic running time. The scaling of the critical running time is expressed in terms of the Lambert W function. We derive the transitionless driving Hamiltonian for the adiabatic search algorithm, which makes a quantum state follow the adiabatic path. We demonstrate that a uniform transitionless driving Hamiltonian, approximate to the exact time-dependent driving Hamiltonian, can alter the non-adiabatic transition probability from the inverse square decay to the inverse fourth power decay with the running time. This may open up a new but simple way of speeding up adiabatic quantum dynamics.
Transitionless driving on adiabatic search algorithm.
Oh, Sangchul; Kais, Sabre
2014-12-14
We study quantum dynamics of the adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolution is studied and visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for the short running time to inverse-square decay in asymptotic running time. The scaling of the critical running time is expressed in terms of the Lambert W function. We derive the transitionless driving Hamiltonian for the adiabatic search algorithm, which makes a quantum state follow the adiabatic path. We demonstrate that a uniform transitionless driving Hamiltonian, approximate to the exact time-dependent driving Hamiltonian, can alter the non-adiabatic transition probability from the inverse square decay to the inverse fourth power decay with the running time. This may open up a new but simple way of speeding up adiabatic quantum dynamics. PMID:25494733
Bravaya, Ksenia B.; Kostko, Oleg; Dolgikh, Stanislav; Landau, Arie; Ahmed, Musahid; Krylov, Anna I.
2010-08-02
We report high-level ab initio calculations and single-photon ionization mass spectrometry study of ionization of adenine (A), thymine (T), cytosine (C) and guanine (G). For thymine and adenine, only the lowest-energy tautomers were considered, whereas for cytosine and guanine we characterized five lowest-energy tautomeric forms. The first adiabatic and several vertical ionization energies were computed using equation-of-motion coupled-cluster method for ionization potentials with single and double substitutions. Equilibrium structures of the cationic ground states were characterized by DFT with the {omega}B97X-D functional. The ionization-induced geometry changes of the bases are consistent with the shapes of the corresponding molecular orbitals. For the lowest-energy tautomers, the magnitude of the structural relaxation decreases in the following series G > C > A > T, the respective relaxation energies being 0.41, 0.32, 0.25 and 0.20 eV. The computed adiabatic ionization energies (8.13, 8.89, 8.51-8.67 and 7.75-7.87 eV for A,T,C and G, respectively) agree well with the onsets of the photoionization efficiency (PIE) curves (8.20 {+-} 0.05, 8.95 {+-} 0.05, 8.60 {+-} 0.05 and 7.75 {+-} 0.05 eV). Vibrational progressions for the S{sub 0}-D{sub 0} vibronic bands computed within double-harmonic approximation with Duschinsky rotations are compared with previously reported experimental photoelectron spectra.
Bond selective chemistry beyond the adiabatic approximation
Butler, L.J.
1993-12-01
One of the most important challenges in chemistry is to develop predictive ability for the branching between energetically allowed chemical reaction pathways. Such predictive capability, coupled with a fundamental understanding of the important molecular interactions, is essential to the development and utilization of new fuels and the design of efficient combustion processes. Existing transition state and exact quantum theories successfully predict the branching between available product channels for systems in which each reaction coordinate can be adequately described by different paths along a single adiabatic potential energy surface. In particular, unimolecular dissociation following thermal, infrared multiphoton, or overtone excitation in the ground state yields a branching between energetically allowed product channels which can be successfully predicted by the application of statistical theories, i.e. the weakest bond breaks. (The predictions are particularly good for competing reactions in which when there is no saddle point along the reaction coordinates, as in simple bond fission reactions.) The predicted lack of bond selectivity results from the assumption of rapid internal vibrational energy redistribution and the implicit use of a single adiabatic Born-Oppenheimer potential energy surface for the reaction. However, the adiabatic approximation is not valid for the reaction of a wide variety of energetic materials and organic fuels; coupling between the electronic states of the reacting species play a a key role in determining the selectivity of the chemical reactions induced. The work described below investigated the central role played by coupling between electronic states in polyatomic molecules in determining the selective branching between energetically allowed fragmentation pathways in two key systems.
Studies in Chaotic adiabatic dynamics
Jarzynski, C.
1994-01-01
Chaotic adiabatic dynamics refers to the study of systems exhibiting chaotic evolution under slowly time-dependent equations of motion. In this dissertation the author restricts his attention to Hamiltonian chaotic adiabatic systems. The results presented are organized around a central theme, namely, that the energies of such systems evolve diffusively. He begins with a general analysis, in which he motivates and derives a Fokker-Planck equation governing this process of energy diffusion. He applies this equation to study the {open_quotes}goodness{close_quotes} of an adiabatic invariant associated with chaotic motion. This formalism is then applied to two specific examples. The first is that of a gas of noninteracting point particles inside a hard container that deforms slowly with time. Both the two- and three-dimensional cases are considered. The results are discussed in the context of the Wall Formula for one-body dissipation in nuclear physics, and it is shown that such a gas approaches, asymptotically with time, an exponential velocity distribution. The second example involves the Fermi mechanism for the acceleration of cosmic rays. Explicit evolution equations are obtained for the distribution of cosmic ray energies within this model, and the steady-state energy distribution that arises when this equation is modified to account for the injection and removal of cosmic rays is discussed. Finally, the author re-examines the multiple-time-scale approach as applied to the study of phase space evolution under a chaotic adiabatic Hamiltonian. This leads to a more rigorous derivation of the above-mentioned Fokker-Planck equation, and also to a new term which has relevance to the problem of chaotic adiabatic reaction forces (the forces acting on slow, heavy degrees of freedom due to their coupling to light, fast chaotic degrees).
POTENTIAL HUMAN STUDY POPULATIONS FOR NON-IONIZING (RADIO FREQUENCY) RADIATION HEALTH EFFECTS
This research project was initiated to identify potential human populations for future epidemiological studies of the health effects of radio frequency radiation. Through a literature search and contacts with various groups and organizations, numerous occupations and applications...
Gallandi, Lukas; Marom, Noa; Rinke, Patrick; Körzdörfer, Thomas
2016-02-01
The performance of non-empirically tuned long-range corrected hybrid functionals for the prediction of vertical ionization potentials (IPs) and electron affinities (EAs) is assessed for a set of 24 organic acceptor molecules. Basis set-extrapolated coupled cluster singles, doubles, and perturbative triples [CCSD(T)] calculations serve as a reference for this study. Compared to standard exchange-correlation functionals, tuned long-range corrected hybrid functionals produce highly reliable results for vertical IPs and EAs, yielding mean absolute errors on par with computationally more demanding GW calculations. In particular, it is demonstrated that long-range corrected hybrid functionals serve as ideal starting points for non-self-consistent GW calculations. PMID:26731340
Cruz, C.H.B.; Fragnito, H.L.
1981-02-01
A method for increasing the efficiency of conventional CO/sub 2/ transverse electric atmospheric lasers is presented. We take advantage of the fact that by strongly doping the usual CO/sub 2/:N/sub 2/:He gas mixture with a low ionization potential additive, the plasma sustaining field can be suitably reduced to attain a value optimum for the excitation of the upper laser level of CO/sub 2/. We observed field reductions to as little as 20% of the reported value for the nondoped mixture. This permitted us to increase the CO/sub 2/ excitation efficiency by a factor of 2. We also observed that the laser operating efficiency was increased by reducing the helium concentration in the gas mixture.
Morgan, William F.; Sowa, Marianne B.
2015-01-01
Not-targeted effects represent a paradigm shift from the "DNA centric" view that ionizing radiation only elicits biological effects and subsequent health consequences as a result of an energy deposition event in the cell nucleus. While this is likely true at higher radiation doses (> 1Gy), at low doses (< 100mGy) non-targeted effects associated with radiation exposure might play a significant role. Here definitions of non-targeted effects are presented, the potential mechanisms for the communication of signals and signaling networks from irradiated cells/tissues are proposed, and the various effects of this intra- and intercellular signaling are described. We conclude with speculation on how these observations might lead to and impact long-term human health outcomes.
Su, Neil Qiang; Xu, Xin
2016-05-10
Recently, we have developed an integration approach for the calculations of ionization potentials (IPs) and electron affinities (EAs) of molecular systems at the level of second-order Møller-Plesset (MP2) (Su, N. Q.; Xu, X. J. Chem. Theory Comput. 11, 4677, 2015), where the full MP2 energy gradient with respect to the orbital occupation numbers was derived but only at integer occupations. The theory is completed here to cover the fractional occupation systems, such that Slater's transition state concept can be used to have accurate predictions of IPs and EAs. Antisymmetrized Goldstone diagrams have been employed for interpretations and better understanding of the derived equations, where two additional rules were introduced in the present work specifically for hole or particle lines with fractional occupation numbers. PMID:27010405
An ab initio study of the ionization potentials and f-f spectroscopy of europium atoms and ions.
Naleway, C.; Seth, M.; Shepard, R.; Wagner, A. F.; Tilson, J. L.; Ermler, W. C.; Brozell, S. R.; Stevens Inst. of Tech.; Ohio State Univ.
2002-04-01
The first three ionization potentials of europium and the f-f spectroscopy of the two lowest multiplets of Eu+3 have been calculated using ab initio spin-orbit configuration interaction techniques. To accomplish this, a new averaged relativistic effective core potential has been developed which leaves only the 5s, 5p, and 4f in the valence space. A series of configuration interaction calculations were carried out up through single and partial double excitations with a double-zeta quality basis set. The computed ionization values have an absolute error of about 0.1 eV from the experimental values. The computed f-f spectroscopy for the lowest {sup 7}F multiplet of Eu{sup +3} has a RMS error with experiment of about 100 cm-1. The computed f-f spectroscopy for the first excited {sup 5}D multiplet has a higher RMS error of about 350 cm{sup -1}. The computed center of gravity separation between the {sup 5}D-{sup 7}F multiplet is underestimated by 750 cm{sup -1}. Comparisons between non-spin-orbit and spin-orbit configuration interaction calculations for the separations of the centers of gravity of multiplets are very favorable up through single and double excitations with differences of a tenth of an eV or less. The spin-orbit configuration interaction calculations are among the largest ever performed for lanthanides, with expansion lengths in excess of 1.9 million double-group-adapted functions. The calculations were achieved by application of a new parallel spin-orbit configuration interaction component in the COLUMBUS Program System.
Beste, Ariana; Vazquez-Mayagoitia, Alvaro; Ortiz, J. Vincent
2013-01-01
A direct method (D-Delta-MBPT(2)) to calculate second-order ionization potentials (IPs), electron affinities (EAs), and excitation energies is developed. The Delta-MBPT(2) method is defined as the correlated extension of the Delta-HF method. Energy differences are obtained by integrating the energy derivative with respect to occupation numbers over the appropriate parameter range. This is made possible by writing the second-order energy as a function of the occupation numbers. Relaxation effects are fully included at the SCF level. This is in contrast to linear response theory, which makes the D-Delta-MBPT(2) applicable not only to single excited but also higher excited states. We show the relationship of the D-Delta-MBPT(2) method for IPs and EAs to a second-order approximation of the effective Fock-space coupled-cluster Hamiltonian and a second-order electron propagator method. We also discuss the connection between the D-Delta-MBPT(2) method for excitation energies and the CIS-MP2 method. Finally, as a proof of principle, we apply our method to calculate ionization potentials and excitation energies of some small molecules. For IPs, the Delta-MBPT(2) results compare well to the second-order solution of the Dyson equation. For excitation energies, the deviation from EOM-CCSD increases when correlation becomes more important. When using the numerical integration technique, we encounter difficulties that prevented us from reaching the Delta-MBPT(2) values. Most importantly, relaxation beyond the Hartree Fock level is significant and needs to be included in future research.
NASA Astrophysics Data System (ADS)
Mukherjee, Saikat; Adhikari, Satrajit
2014-08-01
We calculate the adiabatic potential energy surfaces (PESs) and the non-adiabatic coupling terms (NACTs) for the excited electronic states of K3 cluster by MRCI approach using MOLPRO. The NACTs are adapted with molecular symmetry to assign appropriate IREPs so that the elements of the Hamiltonian matrix are totally symmetric. We incorporate those NACTs into three-state adiabatic-to-diabatic transformation (ADT) equations to obtain ADT angles for constructing continuous, single-valued, smooth and symmetric diabatic Hamiltonian matrix, where its elements are fitted with analytic functions. Finally, we demonstrate that the dressed diabatic and adiabatic-via-dressed diabatic PECs show prominent topological effect over dressed adiabatic curves.
Ding, Yuanqing; Liu, Haining; Tekwani, Babu L; Nanayakkara, N P Dhammika; Khan, Ikhlas A; Walker, Larry A; Doerksen, Robert J
2016-07-18
The administration of primaquine (PQ), an essential drug for the treatment and radical cure of malaria, can lead to methemoglobin formation and life-threatening hemolysis for glucose-6-phosphate dehydrogenase deficient patients. The ionization potential (IP, a quantitative measure of the ability to lose an electron) of the metabolites generated by antimalarial 8-aminoquinoline (8-AQ) drugs like PQ has been believed to be correlated in part to this methemoglobinemia hemotoxicity: the lower the IP of an 8-AQ derivative, the higher the concentration of methemoglobin generated. In this work, demethoxylated primaquine (AQ02) was employed as a model, by intensive computation at the B3LYP-SCRF(PCM)/6-311++G**//B3LYP/6-31G** level in water, to study the effects of hydroxylation at various positions on the ionization potential. Compared to the parent AQ02, the IPs of AQ02's metabolites hydroxylated at N1', C5, and C7 were lower by 61, 30, and 19 kJ/mol, respectively, while differences in the IP relative to PQ were small for hydroxylation at all other positions. The C6 position, at which the IP of the hydroxylated metabolite was greater than that of AQ02, by 2 kJ/mol, was found to be unique. Several literature and proposed 8-AQ analogues were studied to evaluate substituent effects on their potential to generate methemoglobin, with the finding that hydroxylations at N1' and C5 contribute the most to the potential hemotoxicity of PQ-based antimalarials, whereas hydroxylation at C7 has little effect. Phenoxylation at C5 in PQ-based 8-AQs can block the hydroxylation at C5 and reduce the potential for methemoglobin generation, while -CF3 and chlorines attached to the phenolic ring can further reduce the risk. The H-shift at N1' during the cationization of hydroxylated metabolites of 8-AQs sharply decreased their IPs, but this effect can be significantly reduced by the introduction of an electron-withdrawing group to the quinoline core. The results and this approach may be
Fukano, Tatsuo; Motohiro, Tomoyoshi; Ida, Takashi; Hashizume, Hiroo
2005-04-15
Indium tin oxide (ITO) films deposited with single layers of monodispersive fluorine-doped tin oxide (FTO) nanoparticles of several nanometers in size were grown on glass substrates by intermittent spray pyrolysis deposition using conventional atomizers. These films have significantly higher ionization potentials than the bare ITO and FTO films grown using the same technique. The ITO films covered with FTO particles of 7 nm in average size show an ionization potential of 5.01 eV, as compared with {approx}4.76 and {approx}4.64 eV in ITO and FTO films, respectively, which decreases as the FTO particle size increases. The ionization potentials are practically invariant against oxidation and reduction treatments, promising a wide application of the films to transparent conducting oxide electrodes in organic electroluminescent devices and light-emitting devices of high efficiencies.
NASA Astrophysics Data System (ADS)
Fukano, Tatsuo; Motohiro, Tomoyoshi; Ida, Takashi; Hashizume, Hiroo
2005-04-01
Indium tin oxide (ITO) films deposited with single layers of monodispersive fluorine-doped tin oxide (FTO) nanoparticles of several nanometers in size were grown on glass substrates by intermittent spray pyrolysis deposition using conventional atomizers. These films have significantly higher ionization potentials than the bare ITO and FTO films grown using the same technique. The ITO films covered with FTO particles of 7nm in average size show an ionization potential of 5.01eV, as compared with ˜4.76 and ˜4.64eV in ITO and FTO films, respectively, which decreases as the FTO particle size increases. The ionization potentials are practically invariant against oxidation and reduction treatments, promising a wide application of the films to transparent conducting oxide electrodes in organic electroluminescent devices and light-emitting devices of high efficiencies.
Robust adiabatic sum frequency conversion.
Suchowski, Haim; Prabhudesai, Vaibhav; Oron, Dan; Arie, Ady; Silberberg, Yaron
2009-07-20
We discuss theoretically and demonstrate experimentally the robustness of the adiabatic sum frequency conversion method. This technique, borrowed from an analogous scheme of robust population transfer in atomic physics and nuclear magnetic resonance, enables the achievement of nearly full frequency conversion in a sum frequency generation process for a bandwidth up to two orders of magnitude wider than in conventional conversion schemes. We show that this scheme is robust to variations in the parameters of both the nonlinear crystal and of the incoming light. These include the crystal temperature, the frequency of the incoming field, the pump intensity, the crystal length and the angle of incidence. Also, we show that this extremely broad bandwidth can be tuned to higher or lower central wavelengths by changing either the pump frequency or the crystal temperature. The detailed study of the properties of this converter is done using the Landau-Zener theory dealing with the adiabatic transitions in two level systems. PMID:19654679
Adiabaticity in open quantum systems
NASA Astrophysics Data System (ADS)
Venuti, Lorenzo Campos; Albash, Tameem; Lidar, Daniel A.; Zanardi, Paolo
2016-03-01
We provide a rigorous generalization of the quantum adiabatic theorem for open systems described by a Markovian master equation with time-dependent Liouvillian L (t ) . We focus on the finite system case relevant for adiabatic quantum computing and quantum annealing. Adiabaticity is defined in terms of closeness to the instantaneous steady state. While the general result is conceptually similar to the closed-system case, there are important differences. Namely, a system initialized in the zero-eigenvalue eigenspace of L (t ) will remain in this eigenspace with a deviation that is inversely proportional to the total evolution time T . In the case of a finite number of level crossings, the scaling becomes T-η with an exponent η that we relate to the rate of the gap closing. For master equations that describe relaxation to thermal equilibrium, we show that the evolution time T should be long compared to the corresponding minimum inverse gap squared of L (t ) . Our results are illustrated with several examples.
Quantum dynamics by the constrained adiabatic trajectory method
Leclerc, A.; Jolicard, G.; Guerin, S.; Killingbeck, J. P.
2011-03-15
We develop the constrained adiabatic trajectory method (CATM), which allows one to solve the time-dependent Schroedinger equation constraining the dynamics to a single Floquet eigenstate, as if it were adiabatic. This constrained Floquet state (CFS) is determined from the Hamiltonian modified by an artificial time-dependent absorbing potential whose forms are derived according to the initial conditions. The main advantage of this technique for practical implementation is that the CFS is easy to determine even for large systems since its corresponding eigenvalue is well isolated from the others through its imaginary part. The properties and limitations of the CATM are explored through simple examples.
Spatial adiabatic passage: a review of recent progress
NASA Astrophysics Data System (ADS)
Menchon-Enrich, R.; Benseny, A.; Ahufinger, V.; Greentree, A. D.; Busch, Th; Mompart, J.
2016-07-01
Adiabatic techniques are known to allow for engineering quantum states with high fidelity. This requirement is currently of large interest, as applications in quantum information require the preparation and manipulation of quantum states with minimal errors. Here we review recent progress on developing techniques for the preparation of spatial states through adiabatic passage, particularly focusing on three state systems. These techniques can be applied to matter waves in external potentials, such as cold atoms or electrons, and to classical waves in waveguides, such as light or sound.
Spatial adiabatic passage: a review of recent progress.
Menchon-Enrich, R; Benseny, A; Ahufinger, V; Greentree, A D; Busch, Th; Mompart, J
2016-07-01
Adiabatic techniques are known to allow for engineering quantum states with high fidelity. This requirement is currently of large interest, as applications in quantum information require the preparation and manipulation of quantum states with minimal errors. Here we review recent progress on developing techniques for the preparation of spatial states through adiabatic passage, particularly focusing on three state systems. These techniques can be applied to matter waves in external potentials, such as cold atoms or electrons, and to classical waves in waveguides, such as light or sound. PMID:27245462
Interaction-induced adiabatic cooling for antiferromagnetism in optical lattices
Dare, A.-M.; Raymond, L.; Albinet, G.; Tremblay, A.-M. S.
2007-08-01
In the experimental context of cold-fermion optical lattices, we discuss the possibilities to approach the pseudogap or ordered phases by manipulating the scattering length or the strength of the laser-induced lattice potential. Using the two-particle self-consistent approach, as well as quantum Monte Carlo simulations, we provide isentropic curves for the two- and three-dimensional Hubbard models at half-filling. These quantitative results are important for practical attempts to reach the ordered antiferromagnetic phase in experiments on optical lattices of two-component fermions. We find that adiabatically turning on the interaction in two dimensions to cool the system is not very effective. In three dimensions, adiabatic cooling to the antiferromagnetic phase can be achieved in such a manner, although the cooling efficiency is not as high as initially suggested by dynamical mean-field theory. Adiabatic cooling by turning off the repulsion beginning at strong coupling is possible in certain cases.
The density temperature and the dry and wet virtual adiabats
NASA Technical Reports Server (NTRS)
Bartlo, J.; Betts, Alan K.
1991-01-01
A density temperature is introduced to represent virtual temperature and potential temperature on thermodynamic diagrams. This study reviews how the dry and wet virtual adiabats can be used to represent stability and air parcel density for unsaturated and cloudy air, and present formula and tabulations.
Effect of the Heat Pipe Adiabatic Region.
Brahim, Taoufik; Jemni, Abdelmajid
2014-04-01
The main motivation of conducting this work is to present a rigorous analysis and investigation of the potential effect of the heat pipe adiabatic region on the flow and heat transfer performance of a heat pipe under varying evaporator and condenser conditions. A two-dimensional steady-state model for a cylindrical heat pipe coupling, for both regions, is presented, where the flow of the fluid in the porous structure is described by Darcy-Brinkman-Forchheimer model which accounts for the boundary and inertial effects. The model is solved numerically by using the finite volumes method, and a fortran code was developed to solve the system of equations obtained. The results show that a phase change can occur in the adiabatic region due to temperature gradient created in the porous structure as the heat input increases and the heat pipe boundary conditions change. A recirculation zone may be created at the condenser end section. The effect of the heat transfer rate on the vapor radial velocities and the performance of the heat pipe are discussed. PMID:24895467
NASA Astrophysics Data System (ADS)
Li, Dafa
2016-05-01
The adiabatic theorem was proposed about 90 years ago and has played an important role in quantum physics. The quantitative adiabatic condition constructed from eigenstates and eigenvalues of a Hamiltonian is a traditional tool to estimate adiabaticity and has proven to be the necessary and sufficient condition for adiabaticity. However, recently the condition has become a controversial subject. In this paper, we list some expressions to estimate the validity of the adiabatic approximation. We show that the quantitative adiabatic condition is invalid for the adiabatic approximation via the Euclidean distance between the adiabatic state and the evolution state. Furthermore, we deduce general necessary and sufficient conditions for the validity of the adiabatic approximation by different definitions.
Etalo, Desalegn W.; De Vos, Ric C.H.; Joosten, Matthieu H.A.J.; Hall, Robert D.
2015-01-01
Laser-ablation electrospray ionization (LAESI)-mass spectrometry imaging has been applied to contrasting plant organs to assess its potential as a procedure for performing in vivo metabolomics in plants. In a proof-of-concept experiment, purple/white segmented Phalaenopsis spp. petals were first analyzed using standard liquid chromatography-mass spectrometry analyses of separate extracts made specifically from the purple and white regions. Discriminatory compounds were defined and putatively annotated. LAESI analyses were then performed on living tissues, and these metabolites were then relocalized within the LAESI-generated data sets of similar tissues. Maps were made to illustrate their locations across the petals. Results revealed that, as expected, anthocyanins always mapped to the purple regions. Certain other (nonvisible) polyphenols were observed to colocalize with the anthocyanins, whereas others were found specifically within the white tissues. In a contrasting example, control and Cladosporium fulvum-infected tomato (Solanum lycopersicum) leaves were subjected to the same procedures, and it could be observed that the alkaloid tomatine has clear heterogeneous distribution across the tomato leaf lamina. Furthermore, LAESI analyses revealed perturbations in alkaloid content following pathogen infection. These results show the clear potential of LAESI-based imaging approaches as a convenient and rapid way to perform metabolomics analyses on living tissues. However, a range of limitations and factors have also been identified that must be taken into consideration when interpreting LAESI-derived data. Such aspects deserve further evaluation before this approach can be applied in a routine manner. PMID:26392264
Continuum ionization transition probabilities of atomic oxygen
NASA Technical Reports Server (NTRS)
Samson, J. R.; Petrosky, V. E.
1973-01-01
The technique of photoelectron spectroscopy was used to obtain the relative continuum transition probabilities of atomic oxygen at 584 A for transitions from 3P ground state into the 4S, D2, and P2 states of the ion. Transition probability ratios for the D2 and P2 states relative to the S4 state of the ion are 1.57 + or - 0.14 and 0.82 + or - 0.07, respectively. In addition, transitions from excited O2(a 1 Delta g) state into the O2(+)(2 Phi u and 2 Delta g) were observed. The adiabatic ionization potential of O2(+)(2 Delta g) was measured as 18.803 + or - 0.006 eV.
Adiabatic Wankel type rotary engine
NASA Technical Reports Server (NTRS)
Kamo, R.; Badgley, P.; Doup, D.
1988-01-01
This SBIR Phase program accomplished the objective of advancing the technology of the Wankel type rotary engine for aircraft applications through the use of adiabatic engine technology. Based on the results of this program, technology is in place to provide a rotor and side and intermediate housings with thermal barrier coatings. A detailed cycle analysis of the NASA 1007R Direct Injection Stratified Charge (DISC) rotary engine was performed which concluded that applying thermal barrier coatings to the rotor should be successful and that it was unlikely that the rotor housing could be successfully run with thermal barrier coatings as the thermal stresses were extensive.
Adiabatic Mass Loss Model in Binary Stars
NASA Astrophysics Data System (ADS)
Ge, H. W.
2012-07-01
onset of dynamical time scale mass transfer; if the ratio of donor to accretor masses exceeds this critical value, the dynamical time scale mass transfer ensues. The grid of criterion for all stars can be used to be the basic input as the binary population synthetic method, which will be improved absolutely. In common envelope evolution, the dissipation of orbital energy of the binary provides the energy to eject the common envelope; the energy budget for this process essentially consists of the initial orbital energy of the binary and the initial binding energies of the binary components. We emphasize that, because stellar core and envelope contribute mutually to each other's gravitational potential energy, proper evaluation of the total energy of a star requires integration over the entire stellar interior, not the ejected envelope alone as commonly assumed. We show that the change in total energy of the donor star, as a function of its remaining mass along an adiabatic mass-loss sequence, can be calculated. This change in total energy of the donor star, combined with the requirement that both remnant donor and its companion star fit within their respective Roche lobes, then circumscribes energetically possible survivors of common envelope evolution. It is the first time that we can calculate the accurate total energy of the donor star in common envelope evolution, while the results with the old method are inconsistent with observations.
Pathak, Himadri; Sasmal, Sudip; Nayak, Malaya K; Vaval, Nayana; Pal, Sourav
2016-08-21
The open-shell reference relativistic equation-of-motion coupled-cluster method within its four-component description is successfully implemented with the consideration of single- and double- excitation approximations using the Dirac-Coulomb Hamiltonian. At the first attempt, the implemented method is employed to calculate ionization potential value of heavy atomic (Ag, Cs, Au, Fr, and Lr) and molecular (HgH and PbF) systems, where the effect of relativity does really matter to obtain highly accurate results. Not only the relativistic effect but also the effect of electron correlation is crucial in these heavy atomic and molecular systems. To justify the fact, we have taken two further approximations in the four-component relativistic equation-of-motion framework to quantify how the effect of electron correlation plays a role in the calculated values at different levels of theory. All these calculated results are compared with the available experimental data as well as with other theoretically calculated values to judge the extent of accuracy obtained in our calculations. PMID:27544090
Rooman, Marianne; Wintjens, René
2014-04-01
DNA is subject to oxidative damage due to radiation or by-products of cellular metabolism, thereby creating electron holes that migrate along the DNA stacks. A systematic computational analysis of the dependence of the electronic properties of nucleobase stacks on sequence and conformation was performed here, on the basis of single- and double-stranded homo-nucleobase stacks of 1-10 bases or 1-8 base pairs in standard A-, B-, and Z-conformation. First, several levels of theory were tested for calculating the vertical ionization potentials of individual nucleobases; the M06-2X/6-31G* hybrid density functional theory method was selected by comparison with experimental data. Next, the vertical ionization potential, and the Mulliken charge and spin density distributions were calculated and considered on all nucleobase stacks. We found that (1) the ionization potential decreases with the number of bases, the lowest being reached by Gua≡Cyt tracts; (2) the association of two single strands into a double-stranded tract lowers the ionization potential significantly (3) differences in ionization potential due to sequence variation are roughly three times larger than those due to conformational modifications. The charge and spin density distributions were found (1) to be located toward the 5'-end for single-stranded Gua-stacks and toward the 3'-end for Cyt-stacks and basically delocalized over all bases for Ade- and Thy-stacks; (2) the association into double-stranded tracts empties the Cyt- and Thy-strands of most of the charge and all the spin density and concentrates them on the Gua- and Ade-strands. The possible biological implications of these results for transcription are discussed. PMID:23582046
Rooman, Marianne; Wintjens, René
2013-01-01
DNA is subject to oxidative damage due to radiation or by-products of cellular metabolism, thereby creating electron holes that migrate along the DNA stacks. A systematic computational analysis of the dependence of the electronic properties of nucleobase stacks on sequence and conformation was performed here, on the basis of single- and double-stranded homo-nucleobase stacks of 1–10 bases or 1–8 base pairs in standard A-, B-, and Z-conformation. First, several levels of theory were tested for calculating the vertical ionization potentials of individual nucleobases; the M06-2X/6-31G* hybrid density functional theory method was selected by comparison with experimental data. Next, the vertical ionization potential, and the Mulliken charge and spin density distributions were calculated and considered on all nucleobase stacks. We found that (1) the ionization potential decreases with the number of bases, the lowest being reached by Gua≡Cyt tracts; (2) the association of two single strands into a double-stranded tract lowers the ionization potential significantly (3) differences in ionization potential due to sequence variation are roughly three times larger than those due to conformational modifications. The charge and spin density distributions were found (1) to be located toward the 5′-end for single-stranded Gua-stacks and toward the 3′-end for Cyt-stacks and basically delocalized over all bases for Ade- and Thy-stacks; (2) the association into double-stranded tracts empties the Cyt- and Thy-strands of most of the charge and all the spin density and concentrates them on the Gua- and Ade-strands. The possible biological implications of these results for transcription are discussed. PMID:23582046
Failure of geometric electromagnetism in the adiabatic vector Kepler problem
Anglin, J.R.; Schmiedmayer, J.
2004-02-01
The magnetic moment of a particle orbiting a straight current-carrying wire may precess rapidly enough in the wire's magnetic field to justify an adiabatic approximation, eliminating the rapid time dependence of the magnetic moment and leaving only the particle position as a slow degree of freedom. To zeroth order in the adiabatic expansion, the orbits of the particle in the plane perpendicular to the wire are Keplerian ellipses. Higher-order postadiabatic corrections make the orbits precess, but recent analysis of this 'vector Kepler problem' has shown that the effective Hamiltonian incorporating a postadiabatic scalar potential ('geometric electromagnetism') fails to predict the precession correctly, while a heuristic alternative succeeds. In this paper we resolve the apparent failure of the postadiabatic approximation, by pointing out that the correct second-order analysis produces a third Hamiltonian, in which geometric electromagnetism is supplemented by a tensor potential. The heuristic Hamiltonian of Schmiedmayer and Scrinzi is then shown to be a canonical transformation of the correct adiabatic Hamiltonian, to second order. The transformation has the important advantage of removing a 1/r{sup 3} singularity which is an artifact of the adiabatic approximation.
Entropy in Adiabatic Regions of Convection Simulations
NASA Astrophysics Data System (ADS)
Tanner, Joel D.; Basu, Sarbani; Demarque, Pierre
2016-05-01
One of the largest sources of uncertainty in stellar models is caused by the treatment of convection in stellar envelopes. One-dimensional stellar models often make use of the mixing length or equivalent approximations to describe convection, all of which depend on various free parameters. There have been attempts to rectify this by using 3D radiative-hydrodynamic simulations of stellar convection, and in trying to extract an equivalent mixing length from the simulations. In this Letter, we show that the entropy of the deeper, adiabatic layers in these simulations can be expressed as a simple function of {log}g and {log}{T}{{eff}}, which holds potential for calibrating stellar models in a simple and more general manner.
Sliding seal materials for adiabatic engines
NASA Technical Reports Server (NTRS)
Lankford, J.
1985-01-01
The sliding friction coefficients and wear rates of promising carbide, oxide, and nitride materials were measured under temperature, environmental, velocity, loading conditions that are representative of the adiabatic engine environment. In order to provide guidance needed to improve materials for this application, the program stressed fundamental understanding of the mechanisms involved in friction and wear. Microhardness tests were performed on the candidate materials at elevated temperatures, and in atmospheres relevant to the piston seal application, and optical and electron microscopy were used to elucidate the micromechanisms of wear following wear testing. X-ray spectroscopy was used to evaluate interface/environment interactions which seemed to be important in the friction and wear process. Electrical effects in the friction and wear processes were explored in order to evaluate the potential usefulness of such effects in modifying the friction and wear rates in service. However, this factor was found to be of negligible significance in controlling friction and wear.
NASA Astrophysics Data System (ADS)
Kimura, Jun-Ichi; Kawabata, Hiroshi
2014-06-01
numerical mass balance calculation model for the adiabatic melting of a dry to hydrous peridotite has been programmed in order to simulate the trace element compositions of basalts from mid-ocean ridges, back-arc basins, ocean islands, and large igneous provinces. The Excel spreadsheet-based calculator, Hydrous Adiabatic Mantle Melting Simulator version 1 (HAMMS1) uses (1) a thermodynamic model of fractional adiabatic melting of mantle peridotite, with (2) the parameterized experimental melting relationships of primitive to depleted mantle sources in terms of pressure, temperature, water content, and degree of partial melting. The trace element composition of the model basalt is calculated from the accumulated incremental melts within the adiabatic melting regime, with consideration for source depletion. The mineralogic mode in the primitive to depleted source mantle in adiabat is calculated using parameterized experimental results. Partition coefficients of the trace elements of mantle minerals are parameterized to melt temperature mostly from a lattice strain model and are tested using the latest compilations of experimental results. The parameters that control the composition of trace elements in the model are as follows: (1) mantle potential temperature, (2) water content in the source mantle, (3) depth of termination of adiabatic melting, and (4) source mantle depletion. HAMMS1 enables us to obtain the above controlling parameters using Monte Carlo fitting calculations and by comparing the calculated basalt compositions to primary basalt compositions. Additionally, HAMMS1 compares melting parameters with a major element model, which uses petrogenetic grids formulated from experimental results, thus providing better constraints on the source conditions.
Ionization Thresholds of Small Carbon Clusters: Tunable VUVExperiments and Theory
Belau, Leonid; Wheeler, Steven E.; Ticknor, Brian W.; Ahmed,Musahid; Leone, Stephen R.; Allen, Wesley D.; Schaefer III, Henry F.; Duncan, Michael A.
2007-07-31
Small carbon clusters (Cn, n = 2-15) are produced in amolecular beam by pulsed laser vaporization and studied with vacuumultraviolet (VUV) photoionization mass spectrometry. The required VUVradiation in the 8-12 eV range is provided by the Advanced Light Source(ALS) at the Lawrence Berkeley National Laboratory. Mass spectra atvarious ionization energies reveal the qualitative relative abundances ofthe neutral carbon clusters produced. By far the most abundant species isC3. Using the tunability of the ALS, ionization threshold spectra arerecorded for the clusters up to 15 atoms in size. The ionizationthresholds are compared to those measured previously with charge-transferbracketing methods. To interpret the ionization thresholds for differentcluster sizes, new ab initio calculations are carried out on the clustersfor n = 4-10. Geometric structures are optimized at the CCSD(T) levelwith cc-pVTZ (or cc-pVDZ) basis sets, and focal point extrapolations areapplied to both neutral and cation species to determine adiabatic andvertical ionization potentials. The comparison of computed and measuredionization potentials makes it possible to investigate the isomericstructures of the neutral clusters produced in this experiment. Themeasurements are inconclusive for the n = 4-6 species because ofunquenched excited electronic states. However, the data provide evidencefor the prominence of linear structures for the n = 7, 9, 11, 13 speciesand the presence of cyclic C10.