Zhang Yuanjiang; Zhao Qiang
2010-02-01
We investigate the DD production in e{sup +}e{sup -} annihilations near threshold in an effective Lagrangian approach. This shows that the lineshape of the cross section near threshold is sensitive to the contributions from {psi}{sup '}, though it is below the DD threshold. The recent experimental data from the BES and Belle collaborations allow us to determine the {psi}{sup '}DD coupling constant, which appears to be consistent with other theoretical studies. As a consequence, the {psi}{sup '}-{psi}(3770) mixing parameter can be extracted around the {psi}(3770) mass region. Resonance parameters for {psi}(3770), X(3900), {psi}(4040), and {psi}(4160) are also investigated. The X(3900) appears as an enhancement at around 3.9 GeV in the Belle data. In addition to treating it as a resonance, we also study the mechanism through which the enhancement is produced by the DD*+c.c. open channel effects. Our result shows that such a possibility cannot be eliminated.
Low-lying resonances and relativistic screening in Big Bang nucleosynthesis
NASA Astrophysics Data System (ADS)
Famiano, M. A.; Balantekin, A. B.; Kajino, T.
2016-04-01
We explore effects of the screening due to the relativistic electron-positron plasma and presence of resonances in the secondary reactions leading to A =7 nuclei during the Big Bang nucleosynthesis. In particular, we investigate and examine possible low-lying resonances in the 7Be (3He,γ ) 10C reaction and examine the resultant destruction of 7Be for various resonance locations and strengths. While a resonance in the 10C compound nucleus is thought to have negligible effects we explore the possibility of an enhancement from plasma screening that may adjust the final 7Be abundance. We find the effects of relativistic screening and possible low-lying resonances to be relatively small in the standard Early Universe models.
{sup 10}Li low-lying resonances populated by one-neutron transfer
Cavallaro, M. Agodi, C.; Carbone, D.; Cunsolo, A.; De Napoli, M.; Cappuzzello, F.; Bondì, M.; Davids, B.; Galinski, N.; Ruiz, C.; Davinson, T.; Sanetullaev, A.; Foti, A.; Kanungo, R.; Lenske, H.; Orrigo, S. E. A.
2015-10-15
The {sup 9}Li + {sup 2}H → {sup 10}Li + {sup 1}H one-neutron transfer reaction has been performed at 100 MeV incident energy at TRIUMF using a {sup 9}Li beam delivered by the ISAC-II facility. A setup based on double-sided silicon strip detectors has been used in order to detect and identify the outgoing {sup 9}Li produced by the {sup 10}Li breakup at forward angles and the recoil protons emitted at backward angles. The {sup 10}Li low-lying resonances, whose energies, widths and configurations are still unclear, have been populated with significant statistics.
10Li low-lying resonances populated by one-neutron transfer
NASA Astrophysics Data System (ADS)
Cavallaro, M.; De Napoli, M.; Cappuzzello, F.; Agodi, C.; Bondı, M.; Carbone, D.; Cunsolo, A.; Davids, B.; Davinson, T.; Foti, A.; Galinski, N.; Kanungo, R.; Lenske, H.; Orrigo, S. E. A.; Ruiz, C.; Sanetullaev, A.
2015-10-01
The 9Li + 2H → 10Li + 1H one-neutron transfer reaction has been performed at 100 MeV incident energy at TRIUMF using a 9Li beam delivered by the ISAC-II facility. A setup based on double-sided silicon strip detectors has been used in order to detect and identify the outgoing 9Li produced by the 10Li breakup at forward angles and the recoil protons emitted at backward angles. The 10Li low-lying resonances, whose energies, widths and configurations are still unclear, have been populated with significant statistics.
Low-lying even-parity meson resonances and spin-flavor symmetry
Garcia-Recio, C.; Geng, L. S.; Nieves, J.; Salcedo, L. L.
2011-01-01
Based on a spin-flavor extension of chiral symmetry, a novel s-wave meson-meson interaction involving members of the {rho} nonet and of the {pi} octet is introduced, and its predictions are analyzed. The starting point is the SU(6) version of the SU(3)-flavor Weinberg-Tomozawa Lagrangian. SU(6) symmetry-breaking terms are then included to account for the physical meson masses and decay constants in a way that preserves (broken) chiral symmetry. Next, the T-matrix amplitudes are obtained by solving the Bethe-Salpeter equation in a coupled-channel scheme, and the poles are identified with their possible Particle Data Group counterparts. It is shown that most of the low-lying even-parity Particle Data Group meson resonances, especially in the J{sup P}=0{sup +} and 1{sup +} sectors, can be classified according to multiplets of SU(6). The f{sub 0}(1500), f{sub 1}(1420), and some 0{sup +}(2{sup ++}) resonances cannot be accommodated within this scheme, and thus they would be clear candidates to be glueballs or hybrids. Finally, we predict the existence of five exotic resonances (I{>=}3/2 and/or |Y|=2) with masses in the range of 1.4-1.6 GeV, which would complete the 27{sub 1}, 10{sub 3}, and 10{sub 3}* multiplets of SU(3) x SU(2).
Anharmonic Resonances among Low-Lying Vibrational Levels of Methyl Iso-Cyanide (H_3CNC)
NASA Astrophysics Data System (ADS)
Pracna, P.; Urban, J.; Urban, V. S.; Varga, J.; Horneman, V.-M.
2010-06-01
Vibrational levels up to 1000 wn of H_3C-N≡C are currently studied in FTIR spectra together with rotational transitions within these levels. This investigation comprises the low-lying excited vibrational levels of the CNC doubly degenerate bending vibration v8=1^± 1 (267.3 wn), v8=20,± 2 (524.6 wn (A), 545.3 wn (E)), and v8=3^± 1,± 3 (792.5 wn (A1+A2), 833.9 wn (E)), respectively, and the next higher fundamental level of the C-N valence vibration v4=1 (945 wn). All these vibrational levels exhibit cubic and quartic anharmonic resonances localized to moderate values of the rotational quantum number K≤10. Therefore the system of rovibrational levels has to be treated as a global polyad in order to describe all the available data quantitatively. The ground state constants have been improved considerably by extending the assignments to higher J/K rotational states both in the purely rotational spectra recorded in the ground vibrational level and in the ground state combination differences generated from the wavenumbers assigned in the fundamental ν_4 band. Similarities and differences with respect to isoelectronic molecules CH_3CN and CH_3CCH are discussed.
Testing the tetraquark structure for the X resonances in the low-lying region
NASA Astrophysics Data System (ADS)
Kim, Hungchong; Kim, K. S.; Cheoun, Myung-Ki; Jido, Daisuke; Oka, Makoto
2016-07-01
Assuming the four-quark structure for the X resonances in the low-lying region, we calculate their masses using the color-spin interaction. Specifically, the hyperfine masses of the color-spin interaction are calculated for the possible states in spin-0, spin-1, spin-2 channels. The two states in spin-0 channel as well as the two states in spin-1 channel are diagonalized in order to generate the physical hyperfine masses. By matching the difference in hyperfine masses with the splitting in corresponding hadron masses and using the X(3872) mass as an input, we estimate the masses corresponding to the states J^{PC}=0^{++} , 1^{+-} , 2^{++} . We find that the masses of two states in 1^{+-} are close to those of X(3823) , X(3900) , and the mass of the 2^{++} state is close to that of X(3940) . For them, the discrepancies are about ˜ 10 MeV. This may suggest that the quantum numbers of the controversial states are X(3823)=1^{+-} , X(3900)=1^{+-} , X(3940)=2^{++} . In this work, we use the same inputs parameters, the constituent quark masses and the strength of the color-spin interaction, that have been adopted in the previous work on the D - or B -meson excited states. There, it was shown that the four-quark structure can be manifested in their excited states. Thus, our results in this work provide a consistent treatment on open- and hidden-charm mesons as far as the four-quark model is concerned.
Giacoppo, F.; Bello Garrote, F. L.; Eriksen, T. K.; Görgen, A.; Guttormsen, M.; Hagen, T. W.; Larsen, A. C.; Kheswa, B. V.; Klintefjord, M.; Koehler, P. E.; et al
2015-05-28
An excess of strength on the low-energy tail of the giant dipole resonance recently has been observed in the γ-decay from the quasicontinuum of 195,196Pt. The nature of this phenomenon is not yet fully investigated. If this feature is present also in the γ-ray strength of the neutron-rich isotopes, it can affect the neutron-capture reactions involved in the formation of heavy-elements in stellar nucleosynthesis. The experimental level density and γ-ray strength function of 195,196Pt are presented together with preliminary calculations of the corresponding neutron-capture cross sections.
NASA Astrophysics Data System (ADS)
Raeder, S.; Sonnenschein, V.; Gottwald, T.; Moore, I. D.; Reponen, M.; Rothe, S.; Trautmann, N.; Wendt, K.
2011-08-01
In-source resonance ionization spectroscopy was used to identify an efficient and selective three-step excitation/ionization scheme of thorium, suitable for titanium:sapphire (Ti:sa) lasers. The measurements were carried out in the preparation of laser spectroscopic investigations for an identification of the low-lying 229mTh isomer predicted at 7.6 ± 0.5 eV above the nuclear ground state. Using a sample of 232Th, a multitude of optical transitions leading to over 20 previously unknown intermediate states of even parity as well as numerous high-lying odd parity auto-ionizing (AI) states were identified. Level energies were determined with an accuracy of 0.06 cm-1 for intermediate and 0.15 cm-1 for AI states. Using different excitation pathways, an assignment of total angular momenta for several energy levels was possible. One particularly efficient ionization scheme of thorium, exhibiting saturation in all three optical transitions, was studied in detail. For all three levels in this scheme, the isotope shifts of the isotopes 228Th, 229Th and 230Th relative to 232Th were measured. An overall efficiency including ionization, transport and detection of 0.6% was determined, which was predominantly limited by the transmission of the mass spectrometer ion optics.
Giacoppo, F.; Bello Garrote, F. L.; Eriksen, T. K.; Görgen, A.; Guttormsen, M.; Hagen, T. W.; Larsen, A. C.; Kheswa, B. V.; Klintefjord, M.; Koehler, P. E.; Moretto, L. G.; Nyhus, H. T.; Renstrøm, T.; Sahin, E.; Siem, S.; Tornyi, T. G.; Schwengner, R.; Zuber, K.
2015-05-28
An excess of strength on the low-energy tail of the giant dipole resonance recently has been observed in the γ-decay from the quasicontinuum of ^{195,196}Pt. The nature of this phenomenon is not yet fully investigated. If this feature is present also in the γ-ray strength of the neutron-rich isotopes, it can affect the neutron-capture reactions involved in the formation of heavy-elements in stellar nucleosynthesis. The experimental level density and γ-ray strength function of ^{195,196}Pt are presented together with preliminary calculations of the corresponding neutron-capture cross sections.
Coupling vector and pseudoscalar mesons to study baryon resonances
Khemchandani, K. P.; Kaneko, H.; Hosaka, A.; Martinez Torres, A.; Nagahiro, H.
2011-11-01
A study of meson-baryon systems with total strangeness -1 is made within a framework based on the chiral and hidden local symmetries. These systems consist of octet baryons, pseudoscalar and vector mesons. The pseudoscalar meson-baryon (PB) dynamics has been earlier found determinant for the existence of some strangeness -1 resonances, for example, {Lambda}(1405), {Lambda}(1670), etc. The motivation of the present work is to study the effect of coupling the closed vector meson-baryon (VB) channels to these resonances. To do this, we obtain the PB{yields}PB and VB{yields}VB amplitudes from the t-channel diagrams and the PB{r_reversible}VB amplitudes are calculated using the Kroll-Ruddermann term where, considering the vector meson dominance phenomena, the photon is replaced by a vector meson. The calculations done within this formalism reveal a very strong coupling of the VB channels to the {Lambda}(1405) and {Lambda}(1670). In the isospin 1 case, we find evidence for a double pole structure of the {Sigma}(1480) which, like the isospin 0 resonances, is also found to couple strongly to the VB channels. The strong coupling of these low-lying resonances to the VB channels can have important implications on certain reactions producing them.
Vector resonances and electromagnetic nucleon structure
Robert Williams; Siegfried Krewald; Kevin Linen
1995-02-01
Motivated by new, precise magnetic proton form factor data in the timelike region, a hybrid vector meson dominance (hVMD) formalism is employed to investigate the significance of excited vector meson resonances on electromagnetic nucleon structure. We find that the rho (1700), omega (1600), and two previously unobserved states are required to reproduce the local structure seen in the new LEAR data just above the pp-bar threshold. We also investigate sensitivity to the phi meson. The model dependence of our result is tested by introducing an alternative model which couples the isoscalar vector meson states to a hypothetical vector glueball resonance. We obtain nearly identical results from both models, except for GnE(q2) in the spacelike region which is very sensitive to the glueball mass and the effective phi NN coupling.
NASA Astrophysics Data System (ADS)
Morales, A. I.; Benzoni, G.; Watanabe, H.; Nishimura, S.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y.; Lorusso, G.; Patel, Z.; Rice, S.; Sinclair, L.; Söderström, P.-A.; Sumikama, T.; Wu, J.; Xu, Z. Y.; Yagi, A.; Yokoyama, R.; Baba, H.; Avigo, R.; Bello Garrote, F. L.; Blasi, N.; Bracco, A.; Camera, F.; Ceruti, S.; Crespi, F. C. L.; de Angelis, G.; Delattre, M.-C.; Dombradi, Zs.; Gottardo, A.; Isobe, T.; Kojouharov, I.; Kurz, N.; Kuti, I.; Matsui, K.; Melon, B.; Mengoni, D.; Miyazaki, T.; Modamio-Hoyborg, V.; Momiyama, S.; Napoli, D. R.; Niikura, M.; Orlandi, R.; Sakurai, H.; Sahin, E.; Sohler, D.; Shaffner, H.; Taniuchi, R.; Taprogge, J.; Vajta, Zs.; Valiente-Dobón, J. J.; Wieland, O.; Yalcinkaya, M.
2016-03-01
Low-lying excited states in 72Ni have been investigated in an in-flight fission experiment at the RIBF facility of the RIKEN Nishina Center. The combination of the state-of-the-art BigRIPS and EURICA setups has allowed for a very accurate study of the β decay from 72Co to 72Ni, and has provided first experimental information on the decay sequence 72Fe→72Co→72Ni and on the delayed neutron-emission branch 73Co→72Ni . Accordingly, we report nearly 60 previously unobserved γ transitions which deexcite 21 new levels in 72Ni. Evidence for the location of the so-sought-after (42+) ,(62+) , and (81+) seniority states is provided. As well, the existence of a low-spin β -decaying isomer in odd-odd neutron-rich Co isotopes is confirmed for mass A =72 . The new experimental information is compared to simple shell-model calculations including only neutron excitations across the f p g shells. It is shown that, in general, the calculations reproduce well the observed states.
Resonance vector soliton of the Rayleigh wave.
Adamashvili, G T
2016-02-01
A theory of acoustic vector solitons of self-induced transparency of the Rayleigh wave is constructed. A thin resonance transition layer on an elastic surface is considered using a model of a two-dimensional gas of impurity paramagnetic atoms or quantum dots. Explicit analytical expressions for the profile and parameters of the Rayleigh vector soliton with two different oscillation frequencies is obtained, as well as simulations of this nonlinear surface acoustic wave with realistic parameters, which can be used in acoustic experiments. It is shown that the properties of a surface vector soliton of the Rayleigh wave depend on the parameters of the resonance layer, the elastic medium, and the transverse structure of the surface acoustic wave. PMID:26986400
Electron Paramagnetic Resonance -- Nuclear Magnetic Resonance Three Axis Vector Magnetometer
NASA Astrophysics Data System (ADS)
Bulatowicz, Michael; Clark, Philip; Griffith, Robert; Larsen, Michael; Mirijanian, James
2012-06-01
The Northrop Grumman Corporation is leveraging the technology developed for the Nuclear Magnetic Resonance Gyroscope (NMRG) to build a combined Electron Paramagnetic Resonance -- Nuclear Magnetic Resonance (EPR-NMR) magnetometer. The EPR-NMR approach provides a high bandwidth and high sensitivity simultaneous measurement of all three vector components of the magnetic field averaged over the small volume of the sensor's one vapor cell. This poster will describe the history, operational principles, and design basics of the EPR-NMR magnetometer including an overview of the NSD designs developed and demonstrated to date. General performance results will also be presented.
On the low-lying states of TiC
NASA Technical Reports Server (NTRS)
Bauschlicher, C. W., Jr.; Siegbahn, P. E. M.
1984-01-01
The ground and low-lying excited states of TiC are investigated using a CASSCF-externally contracted CI approach. The calculations yield a 3Sigma(+) ground state, but the 1Sigma(+) state is only 780/cm higher and cannot be ruled out. The low-lying states have some triple bond character. The nature of the bonding and origin of the states are discussed.
Low-lying Gamow-Teller transitions in spherical nuclei
Cakmak, N.; Uenlue, S.; Selam, C.
2012-01-15
The Pyatov Method has been used to study the low-lying Gamow-Teller transitions in the mass region of 98 Less-Than-Or-Slanted-Equal-To A Less-Than-Or-Slanted-Equal-To 130. The eigenvalues and eigenfunctions of the total Hamiltonian have been solved within the framework of proton-neutron quasiparticle random-phase approximation. The low-lying {beta} decay log(ft) values have been calculated for the nuclei under consideration.
Low-lying lattice modes of highly uniform pentacene monolayers
NASA Astrophysics Data System (ADS)
He, Rui; Tassi, Nancy G.; Blanchet, Graciela B.; Pinczuk, Aron
2009-06-01
The authors report that monolayers of pentacene grown on a functionalized polymeric substrate display high uniformity that enable observations of Raman spectra of low-lying optical vibrations. The evolution of the frequencies and widths of the modes has been studied in films reaching the single monolayer level. Raman spectra of low-lying lattice modes display major changes when the film thickness changes from 1 to 2 monolayers, revealing that a phase akin to a thin film phase of pentacene already emerges in films of only 2 monolayers.
Experimental investigation of low-lying states of pionic atoms
Amian, W.B.; Cloth, P.; Djaloeis, A.; Filges, D.; Gotta, D.; Kilian, K.; Machner, H.; Morsch, H.P.; Protic, D.; Riepe, G.; Roderburg, E.; von Rossen, P.; Turek, P.; Watzlawik, K.H. ); Jarczyk, L.; Smyrski, J.; Stralkowski, A. ); Budzanowski, A.; Dabrowski, H.; Skwirczynska, I. ); Plendl, H. ); Konijn, J. )
1991-04-10
We propose to study pionic atoms in low-lying states. The pions will be produced with the help of recoil free kinematics at small energies in the laboratory. A dedicated detector will be applied allowing the measurements of the width as well as the energy shift of these states.
The Low-Lying Electronic States of Mg2(+)
NASA Technical Reports Server (NTRS)
Ricca, Alessandra; Bauschlicher, Charles W., Jr.
1994-01-01
The low-lying doublet and quartet states of Mg+ have been studied using a multireference configuration interaction approach. The effect of inner-shell correlation has been included using the core-polarization potential method. The computed spectroscopic constants, lifetimes, and oscillator strengths should help resolve the difference between the recent experiments and previous theoretical calculations.
Organic semiconductor interfaces: low-lying lattice modes of pentacene monolayers
NASA Astrophysics Data System (ADS)
He, Rui; Blanchet, Graciela; Pinczuk, Aron
2010-03-01
Highly uniform monolayers of pentacene that are grown on polymeric substrate of poly alpha-methylstyrene exhibit sharp and intense free exciton luminescence. Large enhancements of Raman scattering intensities at the free exciton resonance enable the first observations of low-lying lattice vibration modes in films reaching the single monolayer level.footnotetextRui He, et al. Appl. Phys. Lett. 94, 223310 (2009). The low- lying modes display characteristic changes when going from a single monolayer to two layers, revealing that a phase akin to a thin film phase of pentacene already emerges in structures of only two monolayers. A simple analysis of mode splittings offers estimates of the strength of inter-layer interactions. The results demonstrate novel venues for ultra-thin film characterization and studies of interface effects in organic molecular semiconductor structures.
Testing resonating vector strength: Auditory system, electric fish, and noise
NASA Astrophysics Data System (ADS)
Leo van Hemmen, J.; Longtin, André; Vollmayr, Andreas N.
2011-12-01
Quite often a response to some input with a specific frequency ν○ can be described through a sequence of discrete events. Here, we study the synchrony vector, whose length stands for the vector strength, and in doing so focus on neuronal response in terms of spike times. The latter are supposed to be given by experiment. Instead of singling out the stimulus frequency ν○ we study the synchrony vector as a function of the real frequency variable ν. Its length turns out to be a resonating vector strength in that it shows clear maxima in the neighborhood of ν○ and multiples thereof, hence, allowing an easy way of determining response frequencies. We study this "resonating" vector strength for two concrete but rather different cases, viz., a specific midbrain neuron in the auditory system of cat and a primary detector neuron belonging to the electric sense of the wave-type electric fish Apteronotus leptorhynchus. We show that the resonating vector strength always performs a clear resonance correlated with the phase locking that it quantifies. We analyze the influence of noise and demonstrate how well the resonance associated with maximal vector strength indicates the dominant stimulus frequency. Furthermore, we exhibit how one can obtain a specific phase associated with, for instance, a delay in auditory analysis.
Vector resonances and electromagnetic nucleon structure
Williams, R.A.; Krewald, S.; Linen, K. )
1995-02-01
Motivated by new, precise magnetic proton form factor data in the timelike reigon, a hybrid vector meson dominance (hVMD) formalism is employed to investigate the significance of excited vector meson rsonances on electromagnetic nucleon structure. We find that the [rho](1700), [omega](1600), and two previously unobserved states are required to reproduce the local structure seen in the new LEAR data just above the [ital p[bar p
A theoretical study of the low-lying states of Ti2 and Zr2
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Partridge, Harry; Langhoff, Stephen R.; Rosi, Marzio
1991-01-01
The low-lying states of Ti2 and the valence isoelectronic Zr2 are examined theoretically by means of a multireference configuration-interaction (MRCI) method. MRCI calculations demonstrate that two of the Zr2 states are very low-lying and that the resulting vertical excitation is consistent with the optical spectrum of Zr2. The ground state is predicted for Ti2 on the basis of valence correlation with the MRCI method and the average coupled-pair functional technique. Calculations of the inner-shell correlation effects are estimated and found to lower the 3Delta g state to a ground state, and another to a very low-lying state. The ground state of Ti2 is assigned to 3Delta g since it is lower than the other state at all levels of correlation and is derived from the same atomic asymptote. This conclusion is supported by the lack of an electron-spin resonance signal but contradicts the absence of subcomponents on the Raman spectral lines.
Transition properties of low-lying states in atomic indium
Sahoo, B. K.; Das, B. P.
2011-07-15
We present here the results of our relativistic many-body calculations of various properties of the first six low-lying excited states of indium. The calculations were performed using the relativistic coupled-cluster method in the framework of the singles, doubles, and partial triples approximation. The lifetime of the [4p{sup 6}]5s{sup 2}5p{sub 3/2} state in this atom is determined. Our results could be used to shed light on the reliability of the lifetime measurements of the excited states of atomic indium that we have considered in the present work.
Spectroscopic study of low-lying {sup 16}N levels
Bardayan, D. W.; Nesaraja, C. D.; Pain, S. D.; Smith, M. S.; O'Malley, P. D.; Cizewski, J. A.; Hatarik, R.; Peters, W. A.; Blackmon, J. C.; Chae, K. Y.; Jones, K. L.; Moazen, B. H.; Paulauskas, S.; Pittman, S. T.; Schmitt, K. T.; Chipps, K. A.; Kozub, R. L.; Shriner, J. F. Jr.; Matei, C.
2008-11-15
The magnitude of the {sup 15}N(n,{gamma}){sup 16}N reaction rate in asymptotic giant branch stars depends directly on the neutron spectroscopic factors of low-lying {sup 16}N levels. A new study of the {sup 15}N(d,p){sup 16}N reaction is reported populating the ground and first three excited states in {sup 16}N. The measured spectroscopic factors are near unity as expected from shell model calculations, resolving a long-standing discrepancy with earlier measurements that had never been confirmed or understood. Updated {sup 15}N(n,{gamma}){sup 16}N reaction rates are presented.
Noncollisional excitation of low-lying states in gaseous nebulae
NASA Technical Reports Server (NTRS)
Rubin, Robert H.
1986-01-01
Consideration is given to the effects of processes other than electron collisional excitation on the energy level populations of species of C, N, and O. It is found that dielectronic as well as direct-radiative recombination may contribute significantly and in some cases be the major input to populating the low-lying metastable levels. It is concluded that the most pronounced changes occur when there is a large effective recombination coefficient to a level and when T(e) is low. The most dramatic change among the forbidden lines occurs for the O II forbidden lines.
Low-lying Collective States in {sup 136}Ba
Scheck, M.; Mukhopadhyay, S.; Crider, B.; Choudry, S. N.; Elhami, E.; Peters, E. E.; McEllistrem, M. T.; Orce, J. N.; Yates, S. W.
2009-01-28
Low-lying collective states in {sup 136}Ba were investigated with (n,n'{gamma}) techniques, including Doppler-shift attenuation lifetime measurements. The level spins, lifetimes, branching ratios, multipole-mixing ratios and transition strengths reveal candidates for symmetric-phonon states up to third order. The 2{sub ms}{sup +} mixed-symmetry state was confirmed as unfragmented and a candidate for a [2{sub 1}{sup +} x 2{sub ms}{sup +}]{sub 3}{sup +} two-phonon mixed-symmetry state is proposed.
Low-lying Level Structure of 150Nd
NASA Astrophysics Data System (ADS)
Chakraborty, A.; Prados-Estévez, F. M.; Yates, S. W.; Choudry, S. N.; Crider, B. P.; Kumar, A.; McEllistrem, M. T.; Mukhopadhyay, S.; Orce, J. N.; Mynk, M. G.; Peters, E. E.; Garrett, P. E.; Kulp, W. D.; Wood, J. L.
2011-10-01
To address the issue of whether the 150Nd nucleus represents an example of a phase transition in the shape degree of freedom or a complex example of shape coexistence, its level structure, up to about 2 MeV excitation and 6 ℏ, has been explored via the (n ,n' γ) reaction at the University of Kentucky accelerator facility. Level lifetimes, in the sub-picosecond regime, were extracted with a Doppler-shift attenuation analysis. A significant extension of the level scheme was possible, and the observed low-lying level structure of 150Nd indicates a close resemblance to its neighboring 152Sm isotone. Results from the ongoing analysis will be presented. This material is based on work supported by the U.S. National Science Foundation under Grant No. PHY-0956310.
On the low lying singlet states of BeO
NASA Technical Reports Server (NTRS)
Bauschlicher, C. W., Jr.; Lengsfield, B. H.; Yarkony, D. R.
1980-01-01
Calculations of the ground and low-lying singlet states of BeO are performed in order to gain an understanding of the techniques needed to treat the excited states of other, more complex, ionic molecules. The MCSCF and CI calculations are based on a Gaussian basis set of slightly better than double zeta plus polarization quality for single configuration descriptions of the states. The calculated X-A and X-B state separations are found to be in agreement with experimental measurements. The 1 Sigma - and 1 Delta states are predicted to lie approximately 40,000 kaysers above the ground state and are identified as the C and D states.The 2 1 Pi state is found to be approximately 15,000 kaysers and the 3 1 Sigma + state is found to be approximately 65,000 kaysers above the ground state.
Fully vectorial laser resonator modeling by vector extrapolation methods
NASA Astrophysics Data System (ADS)
Asoubar, Daniel; Kuhn, Michael; Wyrowski, Frank
2015-02-01
The optimization of multi-parameter resonators requires flexible simulation techniques beyond the scalar approximation. Therefore we generalize the scalar Fox and Li algorithm for the transversal eigenmode calculation to a fully vectorial model. This modified eigenvalue problem is solved by two polynomial-type vector extrapolation methods, namely the minimal polynomial extrapolation and the reduced rank extrapolation. Compared to other eigenvalue solvers these techniques can also be applied to resonators including nonlinear components. As an example we show the calculation of an azimuthally polarized eigenmode emitted by a resonator containing a discontinuous phase element and a nonlinear active medium. The simulation is verified by experiments.
Low-lying continuum states of drip-line oxygen isotopes
NASA Astrophysics Data System (ADS)
Tsukiyama, Koshiroh; Otsuka, Takaharu; Fujimoto, Rintaro
2015-09-01
Low-lying continuum states of exotic oxygen isotopes with A=23-26 are studied, by introducing the continuum-coupled shell model (CCSM) characterized by an infinite wall placed very far away and by an interaction for continuum coupling constructed in a close relation to the realistic shell-model Hamiltonian. Neutron-emission spectra from exotic oxygen isotopes are calculated by the doorway-state approach in heavy-ion multi-nucleon transfer reactions. The results agree with experiment remarkably well, providing evidence that the continuum effects are stronger than ˜ 1 MeV, consistent with the shell evolution in exotic nuclei. The peaks in the neutron spectra are understood as doorway-state resonances. The results by this CCSM doorway-state approach are compared with calculations on neutron-scattering resonance peaks made within the CCSM phase-shift approach and also with those obtained in the Gamow shell model, by taking the same Hamiltonian.
Low-Lying Electronic States of CuAu.
Alizadeh Sanati, Davood; Andrae, Dirk
2016-07-28
Coinage metal diatomic molecules are building blocks for nanostructured materials, electronic devices, and catalytically or photochemically active systems that are currently receiving lively interest in both fundamental and applied research. The theoretical study presented here elucidates the electronic structure in the ground and several low-lying excited states of the diatomic molecule CuAu that result from the combination of the atoms in their ground states nd(10)(n + 1)s(1 2)S and lowest excited d-hole states nd(9)(n + 1)s(2 2)D (n = 3 for Cu, n = 5 for Au). Full and smooth potential energy curves, obtained at the multireference configuration interaction (MRCI) level of theory, are presented for the complete set of the thus resulting 44 Λ-S terms and 86 Ω terms. Our approach is based on a scalar relativistic description using the Douglas-Kroll-Hess (DKH) Hamiltonian, with subsequent perturbative inclusion of spin-orbit (SO) coupling via the spin-orbit terms of the Breit-Pauli (BP) Hamiltonian. The Ω terms span an energy interval of about 7 eV at the ground state's equilibrium distance. Spectroscopic constants, calculated for all terms, are shown to accurately reproduce the observation for those nine terms that are experimentally known. PMID:27379475
Low-lying excitations in a strongly interacting Fermi gas
NASA Astrophysics Data System (ADS)
Vale, Christopher; Hoinka, Sascha; Dyke, Paul; Lingham, Marcus
2016-05-01
We present measurements of the low-lying excitation spectrum of a strongly interacting Fermi gas across the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) crossover using Bragg spectroscopy. By focussing the Bragg lasers onto the central volume of the cloud we can probe atoms at near-uniform density allowing measurement of the homogeneous density-density response function. The Bragg wavevector is set to be approximately half of the Fermi wavevector to probe the collective response. Below the superfluid transition temperature the Bragg spectra dominated by the Bogoliubov-Anderson phonon mode. Single particle excitations become visible at energies greater than twice the pairing gap. As interactions are tuned from the BCS to BEC regime the phonon and single particle modes separate apart and both the pairing gap and speed of sound can be directly read off in certain regions of the crossover. Single particle pair-breaking excitations become heavily suppressed as interactions are tuned from the BCS to BEC regimes.
Low-lying isomeric levels in 75Cu
Daugas, J. M.; Faul, T.; Grawe, H.; Pfutzner, M.; Grzywacz, R.; Lewitowicz, M.; Achouri, N. L.; Bentida, R.; Beraud, R.; Borcea, C.; Bingham, C. R.; Catford, W.; Emsallem, A.; De France, G.; Grzywacz, K. L.; Lemmon, R.; Lopez Jimenez, M. J.; de Oliveira Santos, F.; Regan, P. H.; Rykaczewski, Krzysztof Piotr; Sauvestre, J. E.; Sawicka, M.; Stanoiu, M.; Sieja, K.; Nowacki, F.
2010-01-01
Isomeric low-lying states were identified and investigated in the 75Cu nucleus. Two states at 61.8(5)- and 128.3(7)-keV excitation energies with half-lives of 370(40)- and 170(15)-ns were assigned as 75m1Cu and 75m2Cu, respectively. The measured half-lives combined with the recent spin assignment of the ground state allow one to deduce tentatively spin and parity of the two isomers and the dominant multipolarities of the isomeric transitions with respect to the systematics of the Cu isotopes. Shell-model calculations using an up-to-date effective interaction reproduce the evolution of the 1/2 , 3/2 , and 5/2 states for the neutron-rich odd-mass Cu isotopes when filling the g9/2. The results indicate a significant change in the nuclear structure in this region, where a single-particle 5/2 state coexists with more and more collective 3/2 and 1/2 levels at low excitation energies.
Low-lying isomeric levels in {sup 75}Cu
Daugas, J. M.; Faul, T.; Sauvestre, J. E.; Grawe, H.; Pfuetzner, M.; Sawicka, M.; Grzywacz, R.; Lewitowicz, M.; France, G. de; Lopez Jimenez, M. J.; Oliveira Santos, F. de; Baiborodin, D.; Bentida, R.; Beraud, R.; Emsallem, A.; Bingham, C. R.; Grzywacz, K. L.
2010-03-15
Isomeric low-lying states were identified and investigated in the {sup 75}Cu nucleus. Two states at 61.8(5)- and 128.3(7)-keV excitation energies with half-lives of 370(40)- and 170(15)-ns were assigned as {sup 75m1}Cu and {sup 75m2}Cu, respectively. The measured half-lives combined with the recent spin assignment of the ground state allow one to deduce tentatively spin and parity of the two isomers and the dominant multipolarities of the isomeric transitions with respect to the systematics of the Cu isotopes. Shell-model calculations using an up-to-date effective interaction reproduce the evolution of the 1/2{sup -}, 3/2{sup -}, and 5/2{sup -} states for the neutron-rich odd-mass Cu isotopes when filling the nug{sub 9/2}. The results indicate a significant change in the nuclear structure in this region, where a single-particle 5/2{sup -} state coexists with more and more collective 3/2{sup -} and 1/2{sup -} levels at low excitation energies.
On the low-lying states of CuO
NASA Technical Reports Server (NTRS)
Bagus, P. S.; Nelin, C. J.; Bauschlicher, C. W., Jr.
1984-01-01
Self consistent field and correlated wave functions have been computed for the ground and for several low-lying states of CuO. The ground state is X(2)PI and the lowest excited state, at approximately 8,000/cm above X(2)PI, is a previously unidentified 2-sigma(+) state. The separation of these states is compared to that for the similar states of KO and is analysed in terms of integrals between orbitals of the separated free ions. A classification of the states of the molecule based on states of Cu(+) and O(-) which leads to a division into manifolds of states arising from Cu(+) 3d(10) and Cu(+) 3d(9) 4s(1) is considered. It is predicted that the state of the 3d(9) 4s(1) manifold are 10,000 to 30,000/cm above the ground state and assign the observed A2-sigma(+) state at 16,500/cm to this manifold.
Black holes with a single Killing vector field: black resonators
NASA Astrophysics Data System (ADS)
Dias, Óscar J. C.; Santos, Jorge E.; Way, Benson
2015-12-01
We numerically construct asymptotically anti-de Sitter (AdS) black holes in four dimensions that contain only a single Killing vector field. These solutions, which we coin black resonators, link the superradiant instability of Kerr-AdS to the nonlinear weakly turbulent instability of AdS by connecting the onset of the superradiance instability to smooth, horizonless geometries called geons. Furthermore, they demonstrate non-uniqueness of Kerr-AdS by sharing asymptotic charges. Where black resonators coexist with Kerr-AdS, we find that the black resonators have higher entropy. Nevertheless, we show that black resonators are unstable and comment on the implications for the endpoint of the superradiant instability.
Park, In Ja; Yu, Chang Sik; Lim, Seok-Byung; Lee, Jong Lyul; Kim, Chan Wook; Yoon, Yong Sik; Park, Seong Ho; Kim, Jin Cheon
2016-01-01
Abstract The present study explored the benefit of preoperative chemoradiotherapy (PCRT) for sphincter preservation in locally advanced low-lying rectal cancer patients who underwent stapled anastomosis, especially in those with deep and narrow pelvises determined by magnetic resonance imaging. Patients with locally advanced low-lying rectal cancer (≤5 cm from the anal verge) who underwent stapled anastomosis were included. Patients were categorized into two groups (PCRT+ vs. PCRT–) according to PCRT application. Patients in the PCRT+ group were matched to those in the PCRT– group according to potential confounding factors (age, gender, clinical stage, and body mass index) for sphincter preservation. Sphincter preservation, permanent stoma, and anastomosis-related complications were compared between the groups. Pelvic magnetic resonance imaging was used to measure 12 dimensions representing pelvic cavity depth and width with which deep and narrow pelvis was defined. The impact of PCRT on sphincter preservation and permanent stoma in pelvic dimensions defined as deep and narrow pelvis was evaluated, and factors associated with sphincter preservation and permanent stoma were analyzed. One hundred sixty-six patients were one-to-one matched between the PCRT+ and PCRT− groups. Overall, sphincter-saving surgery was performed in 66.3% and the rates were not different between the 2 groups. Anastomotic complications and permanent stoma occurred nonsignificantly more frequently in the PCRT+ group. PCRT was not associated with higher rate of sphincter preservation in all pelvic dimensions defined as deep and narrow pelvis, while PCRT was related to higher rate of permanent stoma in shorter transverse diameter and interspinous distance. On logistic regression analysis, PCRT was not shown to influence both sphincter preservation and permanent stoma, while longer transverse diameter and interspinous distance were associated with lower rate of permanent stoma. PCRT had
Bounding wide composite vector resonances at the LHC
NASA Astrophysics Data System (ADS)
Barducci, Daniele; Delaunay, Cédric
2016-02-01
In composite Higgs models (CHMs), electroweak precision data generically push colourless composite vector resonances to a regime where they dominantly decay into pairs of light top partners. This greatly attenuates their traces in canonical collider searches, tailored for narrow resonances promptly decaying into Standard Model final states. By reinterpreting the CMS same-sign dilepton (SS2 ℓ) analysis at the Large Hadron Collider (LHC), originally designed to search for top partners with electric charge 5/3, we demonstrate its significant coverage over this kinematical regime. We also show the reach of the 13 TeV run of the LHC, with various integrated luminosity options, for a possible upgrade of the SS2ℓ search. The top sector of CHMs is found to be more fine-tuned in the presence of colourless composite resonances in the few TeV range.
Vector and scalar charmonium resonances with lattice QCD
Lang, C. B.; Leskovec, Luka; Mohler, Daniel; Prelovsek, Sasa
2015-09-15
We perform an exploratory lattice QCD simulation of DD¯ scattering, aimed at determining the masses as well as the decay widths of charmonium resonances above open charm threshold. Neglecting coupling to other channels, the resulting phase shift for DD¯scattering in p-wave yields the well-known vector resonance ψ(3770). For m π = 156 MeV, the extracted resonance mass and the decay width agree with experiment within large statistical uncertainty. The scalar charmonium resonances present a puzzle, since only the ground state χ c0(1P ) is well understood, while there is no commonly accepted candidate for its first excitation. We then simulatemore » DD¯scattering in s-wave in order to shed light on this puzzle. The resulting phase shift supports the existence of a yet-unobserved narrow resonance with a mass slightly below 4 GeV. A scenario with this narrow resonance and a pole at χ c0(1P), we found, agrees with the energy-dependence of our phase shift. Further lattice QCD simulations and experimental efforts are needed to resolve the puzzle of the excited scalar charmonia.« less
Vector and scalar charmonium resonances with lattice QCD
Lang, C. B.; Leskovec, Luka; Mohler, Daniel; Prelovsek, Sasa
2015-09-15
We perform an exploratory lattice QCD simulation of DD¯ scattering, aimed at determining the masses as well as the decay widths of charmonium resonances above open charm threshold. Neglecting coupling to other channels, the resulting phase shift for DD¯scattering in p-wave yields the well-known vector resonance ψ(3770). For m _{π} = 156 MeV, the extracted resonance mass and the decay width agree with experiment within large statistical uncertainty. The scalar charmonium resonances present a puzzle, since only the ground state χ _{c0}(1P ) is well understood, while there is no commonly accepted candidate for its first excitation. We then simulate DD¯scattering in s-wave in order to shed light on this puzzle. The resulting phase shift supports the existence of a yet-unobserved narrow resonance with a mass slightly below 4 GeV. A scenario with this narrow resonance and a pole at χ _{c0}(1P), we found, agrees with the energy-dependence of our phase shift. Further lattice QCD simulations and experimental efforts are needed to resolve the puzzle of the excited scalar charmonia.
Low-lying dipole strength of the open-shell nucleus 94Mo
NASA Astrophysics Data System (ADS)
Romig, C.; Beller, J.; Glorius, J.; Isaak, J.; Kelley, J. H.; Kwan, E.; Pietralla, N.; Ponomarev, V. Yu.; Sauerwein, A.; Savran, D.; Scheck, M.; Schnorrenberger, L.; Sonnabend, K.; Tonchev, A. P.; Tornow, W.; Weller, H. R.; Zilges, A.; Zweidinger, M.
2013-10-01
The low-lying dipole strength of the open-shell nucleus 94Mo was studied via the nuclear resonance fluorescence technique up to 8.7 MeV excitation energy at the bremsstrahlung facility at the Superconducting Darmstadt Electron Linear Accelerator (S-DALINAC), and with Compton backscattered photons at the High Intensity γ-ray Source (HIγS) facility. In total, 83 excited states were identified. Exploiting polarized quasi-monoenergetic photons at HIγS, parity quantum numbers were assigned to 41 states excited by dipole transitions. The electric dipole-strength distribution was determined up to 8.7 MeV and compared to microscopic calculations within the quasiparticle phonon model. Calculations and experimental data are in good agreement for the fragmentation, as well as for the integrated strength. The average decay pattern of the excited states was investigated exploiting the HIγS measurements at five energy settings. Mean branching ratios to the ground state and first excited 21+ state were extracted from the measurements with quasi-monoenergetic photons and compared to γ-cascade simulations within the statistical model. The experimentally deduced mean branching ratios exhibit a resonance-like maximum at 6.4 MeV which cannot be reproduced within the statistical model. This indicates a nonstatistical structure in the energy range between 5.5 and 7.5 MeV.
Resonance energy transfer: The unified theory via vector spherical harmonics.
Grinter, Roger; Jones, Garth A
2016-08-21
In this work, we derive the well-established expression for the quantum amplitude associated with the resonance energy transfer (RET) process between a pair of molecules that are beyond wavefunction overlap. The novelty of this work is that the field of the mediating photon is described in terms of a spherical wave rather than a plane wave. The angular components of the field are constructed in terms of vector spherical harmonics while Hankel functions are used to define the radial component. This approach alleviates the problem of having to select physically correct solution from non-physical solutions, which seems to be inherent in plane wave derivations. The spherical coordinate system allows one to easily decompose the photon's fields into longitudinal and transverse components and offers a natural way to analyse near-, intermediate-, and far-zone RET within the context of the relative orientation of the transition dipole moments for the two molecules. PMID:27544087
Two-photon excitation of low-lying electronic quadrupole states in atomic clusters
Nesterenko, V. O.; Reinhard, P.-G.; Halfmann, T.; Pavlov, L. I.
2006-02-15
A simple scheme of population and detection of low-lying electronic quadrupole modes in free small deformed metal clusters is proposed. The scheme is analyzed in terms of the time-dependent local density approximation calculations. As a test case, the deformed cluster Na{sub 11}{sup +} is considered. Long-living quadrupole oscillations are generated via resonant two-photon (two-dipole) excitation and then detected through the appearance of satellites in the photoelectron spectra generated by a probe pulse. Femtosecond pump and probe pulses with intensities I=2x10{sup 10}-2x10{sup 11} W/cm{sup 2} and pulse duration T=200-500 fs are found to be optimal. The modes of interest are dominated by a single electron-hole pair and so their energies, being combined with the photoelectron data for hole states, allow us to gather full mean-field spectra of valence electrons near the Fermi energy. Besides, the scheme allows us to estimate the lifetime of electron-hole pairs and hence the relaxation time of electronic energy into ionic heat.
Barborini, Matteo; Sorella, Sandro; Guidoni, Leonardo
2014-01-01
We present full structural optimizations of the ground state and of the low lying triplet state of the ethylene molecule by means of Quantum Monte Carlo methods. Using the efficient structural optimization method based on renormalization techniques and on adjoint differentiation algorithms recently proposed [Sorella, S.; Capriotti, L. J. Chem. Phys. 2010, 133, 234111], we present the variational convergence of both wave function parameters and atomic positions. All of the calculations were done using an accurate and compact wave function based on Pauling’s resonating valence bond representation: the Jastrow Antisymmetrized Geminal Power (JAGP). All structural and wave function parameters are optimized, including coefficients and exponents of the Gaussian primitives of the AGP and the Jastrow atomic orbitals. Bond lengths and bond angles are calculated with a statistical error of about 0.1% and are in good agreement with the available experimental data. The Variational and Diffusion Monte Carlo calculations estimate vertical and adiabatic excitation energies in the ranges 4.623(10)–4.688(5) eV and 3.001(5)–3.091(5) eV, respectively. The adiabatic gap, which is in line with other correlated quantum chemistry methods, is slightly higher than the value estimated by recent photodissociation experiments. Our results demonstrate how Quantum Monte Carlo calculations have become a promising and computationally affordable tool for the structural optimization of correlated molecular systems. PMID:24634617
Vector resonances from a strong electroweak sector at linear colliders
NASA Astrophysics Data System (ADS)
Casalbuoni, R.; Chiappetta, P.; Deandrea, A.; de Curtis, S.; Dominici, D.; Gatto, R.
1993-06-01
We explore the usefulness of very energetic linear e + e - colliders in the TeV range in studying an alternative scheme of electroweak symmetry breaking based on a strong interacting sector. The calculations are performed within the BESS model which contains new vector resonances. If the mass M V of the new boson multiplet lies not far from the maximum machine energy, or if it is lower, such a resonant contribution would be quite manifest. A result of our analysis is that also virtual effects are important. It appears that annihilation into a fermion pair in such machines, at the considered luminosities, would improve only marginally on existing limits if polarized beams are available and left-right asymmetries are measured. On the other hand, the process of W-pair production by e + e - annihilation would allow for sensitive tests of the hypothesized strong sector, especially if the W polarizations are reconstructed from their decay distributions, and the more so the higher the energy of the machine. An e + e - collider with c.m. energysqrt s = 500 GeV could improve the limits on the model for the range 500< M V (GeV)<1000 when W polarization is not reconstructed. If W polarizations are reconstructed, then the bounds improve for the entire expected range of M V . These bounds become more stringent for larger energy of the collider. We have also studied the detectability of the new resonances through the fusion subprocesses, but this channel does not seem to be interesting even for a collider with a c.m. energysqrt s = 2 TeV.
Low-lying states of valence-hole nuclei in the 208Pb region
NASA Astrophysics Data System (ADS)
Jiang, H.; Shen, J. J.; Zhao, Y. M.; Arima, A.
2011-04-01
Systematic calculations of low-lying states for Ir, Pt, Au, Hg and Tl isotopes with neutron numbers between 120 and 125 have been performed within the framework of the SDG-pair approximation of the shell model. We employ a monopole and quadrupole pairing plus quadrupole-quadrupole-type interaction with optimized parameters, which are assumed to be constants for nuclei with the same proton number or neutron number. We calculate binding energies of the ground states, low energy level schemes, electric quadrupole and magnetic dipole moments, and E2 transition rates. Our results are reasonably consistent with the available experimental data as well as previous theoretical studies, in particular, for low-lying yrast states. We also demonstrate that low-lying states of nuclei studied here are usually well represented by very simple configurations in collective nucleon-pair basis.
Low-lying states of ruthenium isotopes within the nucleon pair approximation
NASA Astrophysics Data System (ADS)
Jiang, H.; Li, B.; Lei, Y.
2016-05-01
Low-lying states of even-even and odd-mass ruthenium isotopes with mass numbers from 95 to 102, including level schemes, electric quadrupole and magnetic dipole moments, and E 2 transition rates, are studied within the framework of the nucleon pair approximation (NPA) of the shell model, by using the phenomenological pairing plus quadrupole interactions. Good agreement is obtained between the calculated results and experimental data. The interesting behaviors of g (J1+) factors versus nuclear spin J (and mass number A ) in even-even Ru-10296 nuclei are analyzed. The dominant configurations of yrast low-lying states in odd-mass Ru-10195 isotopes are discussed in the collective nucleon-pair subspace. The calculated electric quadrupole moments and magnetic moments of low-lying states, many of which have not yet been measured for these nuclei, are useful for future studies.
Energies and Electric Dipole Transitions for Low-Lying Levels of Protactinium IV and Uranium V
NASA Astrophysics Data System (ADS)
Ürer, Güldem; Özdemir, Leyla
2012-02-01
We have reported a relativistic multiconfiguration Dirac-Fock (MCDF) study on low-lying level structures of protactinium IV (Z =91) and uranium V (Z =92) ions. Excitation energies and electric dipole (E1) transition parameters (wavelengths, oscillator strengths, and transition rates) for these low-lying levels have been given. We have also investigated the influence of the transverse Breit and quantum electrodynamic (QED) contributions besides correlation effects on the level structure. A comparison has been made with a few available data for these ions in the literature.
Effects of tensor correlations on low-lying collective states in finite nuclei
Cao Ligang; Sagawa, H.; Colo, G.
2011-03-15
We present a systematic analysis of the effects induced by tensor correlations on low-lying collective states of magic nuclei, by using the fully self-consistent random phase approximation (RPA) model with Skyrme interactions. The role of the tensor correlations is analyzed in detail in the case of quadrupole (2{sup +}) and octupole (3{sup -}) low-lying collective states in {sup 208}Pb. The example of {sup 40}Ca is also discussed, as well as the case of magnetic dipole states (1{sup +}).
Low-lying 1- and 2+ states in 124Sn via inelastic scattering of 17O
NASA Astrophysics Data System (ADS)
Pellegri, L.; Bracco, A.; Crespi, F. C. L.
2016-05-01
The γ decay of low-lying 1-and 2+ states up to the neutron separation energy in 124Sn populate by the inelastic scattering of 17O was measured. The Angular distributions were measured both for the γ rays and the scattered 17O ions. The results are presented.
NASA Astrophysics Data System (ADS)
Margolis, Jack S.; Liu, Karen Y.; Moynihan, Philip I.
1999-01-01
The sensitivity of spectroscopic detection of low-lying gas clouds by an arbitrary spectrometer may be determined by simulating the observation using a high spectral resolution radiative transfer code. The instrumental characteristics may be superimposed on the simulation and the accuracy of the retrieval of the desired parameters may be estimated by use of the covariance matrix.
New extrapolation method for low-lying states of nuclei in the sd and the pf shells
Shen, J. J.; Zhao, Y. M.; Arima, A.; Yoshinaga, N.
2011-04-15
We study extrapolation approaches to evaluate energies of low-lying states for nuclei in the sd and pf shells, by sorting the diagonal matrix elements of the nuclear shell-model Hamiltonian. We introduce an extrapolation method with perturbation and apply our new method to predict both low-lying state energies and E2 transition rates between low-lying states. Our predicted results arrive at an accuracy of the root-mean-squared deviations {approx}40-60 keV for low-lying states of these nuclei.
Low-lying structure of neutron-rich Zn and Ga isotopes
NASA Astrophysics Data System (ADS)
Jiang, H.; Fu, G. J.; Zhao, Y. M.; Arima, A.
2011-09-01
Low-lying states of even-even Zn and odd-mass Ga nuclei with neutron numbers between 42 and 50 have been calculated within the framework of the SDG-pair approximation of the nuclear shell model. We employ a monopole and quadrupole pairing plus quadrupole-quadrupole interaction with optimized parameters, which are assumed to be constants for nuclei with the same proton number or neutron number. We calculate low-lying level schemes, electric quadrupole and magnetic dipole moments, and E2 and M1 transition rates. Reasonable agreement is achieved between the calculated results and experimental data. Dominant configurations in the ground states of odd-mass Ga nuclei are discussed in terms of pair correlations. The weak-coupling picture for some states of odd-mass Ga nuclei is studied.
Calculations of energy levels and lifetimes of low-lying states of barium and radium
Dzuba, V. A.; Ginges, J. S. M.
2006-03-15
We use the configuration-interaction method and many-body perturbation theory to perform accurate calculations of energy levels, transition amplitudes, and lifetimes of low-lying states of barium and radium. Calculations for radium are needed for the planning of measurements of parity- and time-invariance-violating effects which are strongly enhanced in this atom. Calculations for barium are used to control the accuracy of the calculations.
Spectroscopic Properties and Potential Energy Curves of Low-lying electronic States of RuC
Balasubramanian, K; Guo, R
2003-12-22
The RuC molecule has been a challenging species due to the open-shell nature of Ru resulting in a large number of low-lying electronic states. We have carried out state-of-the-art calculations using the complete active space multi-configuration self-consistent field (CASSCF) followed by multireference configuration interaction (MRCI) methods that included up 18 million configurations, in conjunction with relativistic effects. We have computed 29 low-lying electronic states of RuC with different spin multiplicities and spatial symmetries with energy separations less than 38 000 cm{sup -1}. We find two very closely low-lying electronic states for RuC, viz., {sup 1}{Sigma}{sup +} and {sup 3}{Delta} with the {sup 1}{Sigma}{sup +} being stabilized at higher levels of theory. Our computed spectroscopic constants and dipole moments are in good agreement with experiment although we have reported more electronic states than those that have been observed experimentally. Our computations reveal a strongly bound X{sup 1}{Sigma}{sup +} state with a large dipole moment and an energetically close {sup 3}{Delta} state with a smaller dipole moment. Overall our computed spectroscopic constants of the excited states with energy separations less than 18000 cm{sup -1} agree quite well with those of the corresponding observed states.
Scalar Resonance at 750 GeV as Composite of Heavy Vector-Like Fermions
NASA Astrophysics Data System (ADS)
Liao, Wei; Zheng, Han-Qing
2016-08-01
We study a model of scalars which includes both the SM Higgs and a scalar singlet as composites of heavy vector-like fermions. The vector-like fermions are bounded by the super-strong four-fermion interactions. The scalar singlet decays to SM vector bosons through loop of heavy vector-like fermions. We show that the surprisingly large production cross section of di-photon events at 750 GeV resonance and the odd decay properties can all be explained. This model serves as a good model for both SM Higgs and a scalar resonance at 750 GeV. Supported by National Natural Science Foundation of China (NSFC) under Grant Nos. 11135009, 11375065 and 10925522
Wolf, A.; Zamfir, N.V.; Caprio, M.A.; Berant, Z.; Brenner, D.S.; Pietralla, N.; Gill, R.L.; Casten, R.F.; Beausang, C.W.; Kruecken, R.; Zyromski, K.E.; Barton, C.J.; Cooper, J.R.; Hecht, A.A.; Newman, H.; Novak, J.R.; Cederkall, J.
2002-08-27
A study of the low-lying levels of 128Ba was performed using three clover detectors in a compact arrangement. The decay properties of several low-lying states were investigated, spin assignments were made for two states, and several E2/M1 mixing ratios were determined.
Microscopic study of low-lying collective bands in 77 Kr
NASA Astrophysics Data System (ADS)
Tripathy, K. C.; Sahu, R.; Mishra, S.
2006-02-01
The structure of the collective bands in ^{77}Kr is investigated within our deformed shell model (DSM) based on Hartree-Fock states. The different levels are classified into collective bands on the basis of their B(E2) values. The calculated K= 5/2^+ ground band agrees reasonably well with the experiment. An attempt has been made to study the structure of the 3-quasiparticle band based on large J state in this nucleus. The calculated collective bands, the B(E2), and B(M1) values are compared with available experimental data. The nature of alignments in the low-lying bands is also analyzed.
Regularities of low-lying states with random interactions in the fermion dynamical symmetry model
NASA Astrophysics Data System (ADS)
Fu, G. J.; Zhao, Y. M.; Arima, A.
2014-12-01
In this paper we study low-lying states under random interactions in the framework of the fermion dynamical symmetry model (FDSM), regardless of the ground state spin. Very strong correlations are found for R6 versus R4 (where RI≡EI1+/E21+ ) for the entire ensemble. We present arguments on the origin of these regular patterns in terms of the dynamical symmetries of the FDSM. The regular patterns of B (E 2 ;41+→21+) versus B (E 2 ;21+→01+) are found.
Origin of low-lying enhanced E1 strength in rare-Earth nuclei.
Spieker, M; Pascu, S; Zilges, A; Iachello, F
2015-05-15
The experimental E1 strength distribution below 4 MeV in rare-earth nuclei suggests a local breaking of isospin symmetry. In addition to the octupole states, additional J^{π}=1^{-} states with enhanced E1 strength have been observed in rare-earth nuclei by means of (γ,γ') experiments. By reproducing the experimental results, the spdf interacting boson model calculations provide further evidence for the formation of an α cluster in medium-mass nuclei and might provide a new understanding of the origin of low-lying E1 strength. PMID:26024168
Low-Lying Structure of 132,134Xe from Inelastic Neutron Scattering
NASA Astrophysics Data System (ADS)
Peters, E. E.; Chakraborty, A.; Crider, B. P.; Kumar, A.; Prados-Estèvez, F. M.; Ashley, S. F.; Elhami, E.; Mukhopadhyay, S.; Orce, J. N.; McEllistrem, M. T.; Yates, S. W.
2013-03-01
The low-lying structure of 132Xe and 134Xe has been studied using the (n, n' γ) reaction at the University of Kentucky 7-MV Van de Graaff accelerator facility. Gamma-ray excitation function and angular distribution measurements were performed. Lifetimes were measured using the Doppler-shift attenuation method, and transition probabilities were obtained. Previous assignments of mixed-symmetry states in each nucleus are supported. Also, a tentative Jπ = 0+ state is supported for 134Xe, and a new one is proposed for 134Xe.
Low-Lying Dirac Eigenmodes, Topological Charge Fluctuations and the Instanton Liquid Model
I. Horvath; S.J. Dong; T. Draper; F.X. Lee; H.B. Thacker; J.B. Zhang
2002-05-01
The local structure of low-lying eigenmodes of the overlap Dirac operator is studied. It is found that these modes cannot be described as linear combinations of 't Hooft ''would-be'' zeromodes associated with instanton excitations that underly the Instanton Liquid Model. This implies that the instanton liquid scenario for spontaneous chiral symmetry breaking in QCD is not accurate. More generally, our data suggests that the vacuum fluctuations of topological charge are not effectively dominated by localized lumps of unit charge with which the topological ''would-be'' zeromodes could be associated.
STS-31 Discovery, OV-103, rockets through low-lying clouds after KSC liftoff
NASA Technical Reports Server (NTRS)
1990-01-01
STS-31 Discovery, Orbiter Vehicle (OV) 103, rides above the firey glow of the solid rocket boosters (SRBs) and space shuttle main engines (SSMEs) and a long trail of exhaust as it heads toward Earth orbit. Kennedy Space Center (KSC) Launch Complex (LC) Pad 39B is covered in an exhaust cloud moments after the liftoff of OV-103 at 8:33:51.0492 am (Eastern Daylight Time (EDT)). The exhaust plume pierces the low-lying clouds as OV-103 soars into the clear skies above. A nearby waterway appears in the foreground.
STS-31 Discovery, OV-103, is hidden in low-lying clouds after KSC liftoff
NASA Technical Reports Server (NTRS)
1990-01-01
STS-31 Discovery, Orbiter Vehicle (OV) 103, is hidden in low-lying cloud cover as it rises above Kennedy Space Center (KSC) Launch Complex (LC) Pad 39B just after its liftoff at 8:33:51.0492 am (Eastern Daylight Time (EDT)). The glow of the solid rocket booster (SRB) and the space shuttle main engine (SSME) firings appears just below the cloud cover and is reflected in the nearby waterway (foreground). An exhaust plume trails from OV-103 and its SRBs and covers the launch pad area.
Computed potential surfaces for six low-lying states of Ni3
NASA Technical Reports Server (NTRS)
Walch, Stephen P.
1987-01-01
Selected portions of the potential surfaces for six low lying states of Ni3 are the subject of the present SCF/CCI calculations using the effective core potentials developed by Hay and Wadt (1985); the four states are studied for near-equilateral triangle geometries are within 0.04 eV of each other. Two states are studied for linear geometries, of which the first is 0.16 eV higher than the corresponding near-equilateral triangle state and the second is estimated to be nearly degenerate with the near-equilateral triangle structures.
A numerical study of the thermal stability of low-lying coronal loops
NASA Technical Reports Server (NTRS)
Klimchuk, J. A.; Antiochos, S. K.; Mariska, J. T.
1986-01-01
The nonlinear evolution of loops that are subjected to a variety of small but finite perturbations was studied. Only the low-lying loops are considered. The analysis was performed numerically using a one-dimensional hydrodynamical model developed at the Naval Research Laboratory. The computer codes solve the time-dependent equations for mass, momentum, and energy transport. The primary interest is the active region filaments, hence a geometry appropriate to those structures was considered. The static solutions were subjected to a moderate sized perturbation and allowed to evolve. The results suggest that both hot and cool loops of the geometry considered are thermally stable against amplitude perturbations of all kinds.
NASA Astrophysics Data System (ADS)
Es'kin, V. A.; Ivoninsky, A. V.; Kudrin, A. V.; Krafft, C.
2016-01-01
The energy-flow structure during the resonance scattering of a normally incident plane electromagnetic H wave by a gyrotropic cylinder is studied. The main attention is focused on the bifurcations of the time-averaged Poynting vector field at the surface and volume plasmon resonances in the case where the cylinder is aligned with a gyrotropy axis. The behaviour of the Poynting vector field in this case is compared with that observed during the scattering by an isotropic cylinder, and significant differences in the energy-flow structures in the two cases are revealed. Conditions are found under which the maximum magnitude of the Poynting vector at the boundary of a gyrotropic cylinder turns out to be much greater than that at the boundary of an isotropic scatterer of the same shape and size.
Low-Lying Structure of 50Ar and the N =32 Subshell Closure
NASA Astrophysics Data System (ADS)
Steppenbeck, D.; Takeuchi, S.; Aoi, N.; Doornenbal, P.; Matsushita, M.; Wang, H.; Utsuno, Y.; Baba, H.; Go, S.; Lee, J.; Matsui, K.; Michimasa, S.; Motobayashi, T.; Nishimura, D.; Otsuka, T.; Sakurai, H.; Shiga, Y.; Shimizu, N.; Söderström, P.-A.; Sumikama, T.; Taniuchi, R.; Valiente-Dobón, J. J.; Yoneda, K.
2015-06-01
The low-lying structure of the neutron-rich nucleus 50Ar has been investigated at the Radioactive Isotope Beam Factory using in-beam γ -ray spectroscopy with 9Be (54Ca, 50Ar +γ )X , 9Be (55Sc, 50Ar +γ )X , and 9Be (56Ti, 50Ar +γ )X multinucleon removal reactions at ˜220 MeV /u . A γ -ray peak at 1178(18) keV is reported and assigned as the transition from the first 2+ state to the 0+ ground state. A weaker, tentative line at 1582(38) keV is suggested as the 41+→21+ transition. The experimental results are compared to large-scale shell-model calculations performed in the s d p f model space using the SDPF-MU effective interaction with modifications based on recent experimental data for exotic calcium and potassium isotopes. The modified Hamiltonian provides a satisfactory description of the new experimental results for 50Ar and, more generally, reproduces the energy systematics of low-lying states in neutron-rich Ar isotopes rather well. The shell-model calculations indicate that the N =32 subshell gap in 50Ar is similar in magnitude to those in 52Ca and 54Ti and, notably, predict an N =34 subshell closure in 52Ar that is larger than the one recently reported in 54Ca.
Low-lying {Lambda} baryons with spin 1/2 in two-flavor lattice QCD
Takahashi, Toru T.; Oka, Makoto
2010-02-01
Low-lying {Lambda} baryons with spin 1/2 are analyzed in full (unquenched) lattice QCD. We construct 2x2 cross correlators from flavor SU(3) octet and singlet baryon operators, and diagonalize them so as to extract information of two low-lying states for each parity. The two-flavor CP-PACS gauge configurations are used, which are generated in the renormalization-group improved gauge action and the O(a)-improved quark action. Three different {beta}'s, {beta}=1.80, 1.95, and 2.10, are employed, whose corresponding lattice spacings are a=0.2150, 0.1555, and 0.1076 fm. For each cutoff, we use four hopping parameters, ({kappa}{sub val},{kappa}{sub sea}), which correspond to the pion masses ranging about from 500 MeV to 1.1 GeV. Results indicate that there are two negative-parity {Lambda} states nearly degenerate at around 1.6 GeV, while no state as low as {Lambda}(1405) is observed. By decomposing the flavor components of each state, we find that the lowest (1st-excited) negative-parity state is dominated by flavor-singlet (flavor-octet) component. We also discuss meson-baryon components of each state, which has drawn considerable attention in the context of multiquark pictures of {Lambda}(1405).
On the nature of an emergent symmetry in QCD with low-lying Dirac modes removed
NASA Astrophysics Data System (ADS)
Cohen, Thomas D.
2016-02-01
Remarkable symmetry properties appear to arise in lattice calculations of correlation functions in which the lowest-lying eigenmodes of the Dirac operator in quark propagators are removed by hand. The Banks-Casher relation ties the chiral condensate to the density of low-lying modes; thus, it is plausible that removal of such modes could lead to a regime where spontaneous chiral symmetry breaking does not occur. Surprising, a pattern of identical correlation functions was observed that is larger than can be explained by a restoration of chiral symmetry. This suggests that a larger symmetry—one that is not present in the QCD Lagrangian—emerges when these modes are removed. Previously it was argued that this emergent symmetry was SU(4). However, when the low-lying modes are removed, the correlation functions of sources in the SU(4) 15-plet of spin-1 mesons appear to coincide with the correlation function of the SU(4) singlet. A natural explanation for this is an emergent symmetry larger than SU(4). In this work, it is shown that there exists no continuous symmetry whose generators in the field theory are spatial integrals of local operators that can account for the full pattern of identical correlation functions unless the apparent coincidence of the singlet channel with the 15-plet is accidental.
Ozone absorption spectroscopy in search of low-lying electronic states
NASA Technical Reports Server (NTRS)
Anderson, S. M.; Mauersberger, K.
1995-01-01
A spectrometer capable of detecting ozone absorption features 9 orders of magnitude weaker than the Hartley band has been employed to investigate the molecule's near-infrared absorption spectrum. At this sensitivity a wealth of information on the low-lying electronically excited states often believed to play a role in atmospheric chemistry is available in the form of vibrational and rotational structure. We have analyzed these spectra using a combination of digital filtering and isotope substitution and find evidence for three electronically excited states below 1.5 eV. The lowest of these states is metastable, bound by approximately 0.1 eV and probably the (3)A2 rather than the (3)B2 state. Its adiabatic electronic energy is 1.24 +/- 0.01 eV, slightly above the dissociation energy of the ground state. Two higher states, at 1.29 +/- 0.03 and 1.48 +/- 0.03 eV are identified as the (3)B2 and the (3)B1, respectively. Combined with other recent theoretical and experimental data on the low-lying electronic states of ozone, these results imply that these are, in fact, the lowest three excited states; that is, there are no electronically excited states of ozone lying below the energy of O(3P) + O2((3)Sigma(-), v = 0). Some of the implications for atmospheric chemistry are considered.
Kohstall, C.; Belic, D.; Kneissl, U.; Nord, A.; Pitz, H.H.; Scheck, M.; Stedile, F.; Brentano, P. von; Fransen, C.; Gade, A.; Herzberg, R.-D.; Jolie, J.; Linnemann, A.; Pietralla, N.; Werner, V.; Yates, S.W.
2005-09-01
High-resolution nuclear resonance fluorescence experiments (NRF) were performed on {sup 110,111,112,114,116}Cd at the bremsstrahlung facility of the 4.3-MV Dynamitron accelerator in Stuttgart to study the low-lying dipole strength distributions in these vibrational nuclei. Numerous excited states, most of them previously unknown, were observed in the excitation energy range up to 4 MeV. Detailed spectroscopic information has been obtained on excitation energies, spins, decay widths, decay branchings, and transition probabilities. For states in the even-even isotopes {sup 110,112,114,116}Cd, parities could be assigned from linear polarization measurements. Together with our previous results for {sup 108,112,113,114}Cd from NRF studies without polarization measurements, systematics was established for the dipole strength distributions of the stable nuclei within the Cd isotopic chain. The results are discussed with respect to the systematics of E1 two-phonon excitations and mixed-symmetry states in even-even nuclei near the Z=50 shell closure and the fragmentation of these excitation modes in the odd-mass Cd isotopes.
Spectroscopy of low-lying states in neutron-deficient astatine and francium nuclei
NASA Astrophysics Data System (ADS)
Jakobsson, U.; Uusitalo, J.; Auranen, K.; Badran, H.; Cederwall, B.; Cox, D. M.; Grahn, T.; Greenlees, P. T.; Julin, R.; Juutinen, S.; HerzáÅ, A.; Konki, J.; Leino, M.; Mallaburn, M.; Pakarinen, J.; Papadakis, P.; Partanen, J.; Rahkila, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Sorri, J.; Stolze, S.
2015-10-01
Low-lying states in neutron-deficient astatine and francium nuclei have been studied by means of in-beam and delayed spectroscopy. The 13/2+ state has been observed in francium nuclei with a similar down-sloping trend as in neighbouring astatine and bismuth isotopes, as a function of decreasing neutron number. A systematic trend can also now be seen for the 1/2+ state both in astatine and francium nuclei, where the level energy decreases steeply as a function of neutron number when moving further away from the neutron shell closure. This trend is very similar between astatine nuclei and their francium isotones. Moreover, shape coexistence has been observed between the 13/2+ state and the spherical 9/2- ground state in 203Fr and 205Fr.
RDDS lifetime measurements of low-lying superdeformed states in {sup 194}Hg
Kuehn, R.; Dewald, A.; Kruecken, R.
1996-12-31
The lifetimes of three low-lying states in the superdeformed (SD) yrast band of {sup 194}Hg were measured by the recoil-distance Doppler-shift method. The deduced transition quadrupole moments, Q{sub t}, equal those extracted from a DSAM measurement for the high-lying states of the band corroborate the assumption that the decay out of SD bands does not strongly affect the structure of the corresponding states. By a simple mixing-model the decay can be described assuming a very small admixture of normal-deformed (ND) states to the decaying SD states. The deduced ND mixing amplitudes for the yrast SD bands in {sup 192,194}Hg and {sup 194}Pb are presented along with average transition quadrupole moments for the lower parts of the excited SD bands.
Spectroscopy of low-lying states in neutron-deficient astatine and francium nuclei
Jakobsson, U. Cederwall, B.; Uusitalo, J.; Auranen, K.; Badran, H.; Cox, D. M.; Grahn, T.; Greenlees, P. T.; Julin, R.; Juutinen, S.; Herzáň, A.; Konki, J.; Leino, M.; Mallaburn, M.; Pakarinen, J.; Papadakis, P.; Partanen, J.; Rahkila, P.; Sandzelius, M.; Sarén, J.; and others
2015-10-15
Low-lying states in neutron-deficient astatine and francium nuclei have been studied by means of in-beam and delayed spectroscopy. The 13/2{sup +} state has been observed in francium nuclei with a similar down-sloping trend as in neighbouring astatine and bismuth isotopes, as a function of decreasing neutron number. A systematic trend can also now be seen for the 1/2{sup +} state both in astatine and francium nuclei, where the level energy decreases steeply as a function of neutron number when moving further away from the neutron shell closure. This trend is very similar between astatine nuclei and their francium isotones. Moreover, shape coexistence has been observed between the 13/2{sup +} state and the spherical 9/2{sup −} ground state in {sup 203}Fr and {sup 205}Fr.
Regularities in low-lying states of atomic nuclei with random interactions
NASA Astrophysics Data System (ADS)
Fu, G. J.; Shen, J. J.; Zhao, Y. M.; Arima, A.
2015-05-01
In this paper we study low-lying states of atomic nuclei with random interactions, within the framework of the nuclear shell model. The distributions of R6 versus R4 (where RI≡EI1+/E21+ ), empirical proton-neutron interaction, and charge radius are investigated by using a two-body random ensemble. The Mallmann plot exhibits statistical correlations between R6 and R4. The proton-neutron interaction between the last proton and the last neutron in even-A nuclei is found to be stronger than that in odd-A nuclei, and that in N =Z nuclei is even stronger. Simple relations of nuclear charge radii for neighboring nuclei are found to survive remarkably for the random ensemble.
Low-lying hypernuclei in the relativistic quark-gluon model
NASA Astrophysics Data System (ADS)
Gerasyuta, S. M.; Matskevich, E. E.
2013-06-01
Low-lying hypernuclei HΛ3, Σ30H, HeΛ3, Σ30He are described by the relativistic nine-quark equations in the framework of the dispersion relation technique. The approximate solutions of these equations are obtained using a method based on the extraction of leading singularities of the amplitudes. The relativistic nine-quark amplitudes of hypernuclei, including the quarks of three flavors (u,d,s), are calculated. The poles of these amplitudes determine the masses of hypernuclei. The mass of state HΛ3 with the isospin projection I3=0 and the spin-parity JP=(1)/(2)(+)/() is equal to M=2991MeV.
Investigation of solvatochromism in the low-lying singlet states of dithienyl polyenes
NASA Astrophysics Data System (ADS)
Cooper, Thomas M.; Natarajan, Lalgudi V.; Sowards, Laura A.; Spangler, Charles W.
1999-09-01
To understand the low-lying singlet states of dithienyl polyenes, we investigated the solvatochromism of a series of α,ω-di(2-dithienyl 3,4-butyl) polyenes having n=1-5 double bonds. Absorption and emission spectra were collected in a series of aprotic solvents. The absorption energy dispersion effect sensitivity increased smoothly with n, reaching asymptotic behavior as n approached 5. The emission energy had less solvent sensitivity. The trends gave evidence for the existence of a 1B∗u absorbing state and a 1A∗g emitting state. We observed sensitivity of the absorbing and emitting states to solute-solvent electrostatic interactions, suggesting the dithienyl polyenes had a polar ground state conformation.
Low-lying Structure of 132Xe from Inelastic Neutron Scattering
NASA Astrophysics Data System (ADS)
Peters, E. E.; Chakraborty, A.; Crider, B. P.; Kumar, A.; Prados-Estévez, F. M.; Ashley, S. F.; McEllistrem, M. T.; Yates, S. W.
2011-10-01
The stable isotopes of xenon span a region which exhibits the transition from spherical vibrators to gamma-soft nuclei and could thus provide some insight into this lesser understood shape transition. Many measurements to examine the nuclear structure of the xenon isotopes are constrained, however, as xenon is a gas under ambient conditions. Recently, highly enriched samples of 132Xe and 134Xe were converted to solid XeF2 and were studied at the University of Kentucky 7-MV Van de Graaff accelerator facility using inelastic neutron scattering with gamma-ray detection. Lifetimes for some of the low-lying levels were determined via the Doppler-shift attenuation method and reduced transition probabilities were determined. First results of the experiments on 132Xe will be presented. This material is based on work supported by the U.S. National Science Foundation under grant no. PHY-0956310.
Low-lying Structure of ^134Xe from Inelastic Neutron Scattering
NASA Astrophysics Data System (ADS)
Peters, E. E.; Crider, B. P.; Ashley, S. F.; McEllistrem, M. T.; Yates, S. W.
2010-11-01
Unlike the transition from spherical vibrators to axially symmetric rotors, little is known about the transition from spherical vibrators to gamma-soft nuclei. The stable isotopes of xenon span a region which exhibits this lesser understood shape transition. While ^136Xe shows evidence of being a spherical vibrator, the lighter xenon nuclei demonstrate gamma-soft behavior. Measurements to determine the nuclear structure of the xenon isotopes are difficult, however, since they are gases under ambient conditions, and solid targets are much more amenable to typical methods. Recently, highly enriched (>99.9%) samples of ^132Xe and ^134Xe were converted to solid XeF2. These isotopes were studied at the University of Kentucky 7-MV Van de Graaff accelerator facility using the inelastic neutron scattering reaction with gamma-ray detection. Both excitation function and angular distribution data were obtained for the low-lying levels. First results of the experiments on ^134Xe will be presented.
Microscopic structure of low-lying states in {sup 188,190,192}Os
Lo Iudice, N.; Sushkov, A. V.
2008-11-15
The phonon and quasiparticle structure of the low-lying states in {sup 188,190,192}Os is investigated within the microscopic quasiparticle-phonon model. An overall agreement with the data is obtained for energies and transitions. The properties of the 0{sup +} states are found to be correlated with the evolution of the nuclear shape toward the {gamma}-soft region. Special attention is devoted at the 4{sub 3}{sup +} state. This state is found to be composed of a large double-{gamma} phonon component coexisting with an even larger one-phonon hexadecapole piece. Such a mixed phonon structure explains the observed, apparently contradictory, properties of the 4{sub 3}{sup +} states in Os isotopes.
Study of low-lying electronic states of ozone by anion photoelectron spectroscopy of O - 3
NASA Astrophysics Data System (ADS)
Arnold, Don W.; Xu, Cangshan; Kim, Eun H.; Neumark, Daniel M.
1994-07-01
The low-lying electronic states of ozone are studied using anion photoelectron spectroscopy of O-3. The spectra show photodetachment transitions from O-3 to the X˜ 1A1 ground state and to the five lowest lying electronic states of the ozone molecule, namely the 3A2, 3B2, 1A2, 3B1, and 1B1 states. The geometry of the ozonide anion determined from a Franck-Condon analysis of the O3 X 1A1 ground state spectrum agrees reasonably well with previous work. The excited state spectra are dominated by bending vibrational progressions which, for some states, extend well above the dissociation asymptote without noticeable lifetime broadening effects. Preliminary assignments are based upon photoelectron angular distributions and comparison with ab initio calculations. None of the excited states observed lies below the ground state dissociation limit of O3 as suggested by previous experimental and theoretical results.
Low-lying states in 96Nb from the (t,α) reaction
NASA Astrophysics Data System (ADS)
Cloessner, Paul F.; Stöffl, Wolfgang; Sheline, Raymond K.; Lanier, Robert G.
1984-02-01
The nuclear structure of 96Nb has been studied with the (t,α) reaction at 17 MeV on an isotopically enriched target of 97Mo using a quadrupole-three-dipole spectrometer. Measured angular distributions were compared with distorted-wave Born approximation calculations to assign l transfer values. The results are combined with published data and shell model considerations to reassign the 3- state of the low-lying π(p12)1ν(d52)-1 configuration and to confirm the assignments of the spins and parities of the other levels observed. [NUCLEAR REACTIONS 97Mo(t,α)96Nb, Et=17 MeV, enriched target; measured Eα,σ(θ). DWBA analysis. 96Nb deduced levels, Jπ. Compared 96Nb and 92Nb using Pandya relation.
Theoretical study of the low-lying excited states of ABCO, DABCO and homologous cage amines
NASA Astrophysics Data System (ADS)
Galasso, V.
1997-02-01
The electronic spectra of 1-azabicyclo[2.2.2]octane (ABCO), 1,4-diazabicyclo[2.2.2]octane (DABCO), and their [1.1.1] and [3.3.3] congeners have been studied at the ab initio level using the symmetry adapted cluster configuration interaction method. A comprehensive theoretical prediction of the discrete excitation spectra, up to the HOMO → 5s transition, is presented. All the low-lying singlet and triplet electronic states of these symmetric cage amines are found to have essentially Rydberg nature and originate from excitations out of the n-type molecular orbitals. The theoretical results correlate with the available spectroscopic data satisfactorily and provide quantitative support to a number of experimental assignments based on REMPI and MCD measurements.
Ab initio study of low-lying electronic states of SnCl2+.
Lee, Edmond P F; Dyke, John M; Chow, Wan-ki; Mok, Daniel K W; Chau, Foo-tim
2007-12-20
Complete active space self-consistent field (CASSCF), multireference configuration interaction (MRCI), and restricted-spin coupled-cluster singles-doubles with perturbative triples [RCCSD(T)] calculations have been carried out on low-lying doublet and quartet states of SnCl2+, employing basis sets of up to aug-cc-pV5Z quality. Effects of core correlation and off-diagonal spin-orbit interaction on computed vertical ionization energies were investigated. The best theoretical estimate of the adiabatic ionization energy (including zero-point vibrational energy correction) to the X2A1 state of SnCl2+ is 10.093+/-0.010 eV. The first photoelectron band of SnCl2 has also been simulated by employing RCCSD(T)/aug-cc-pV5Z potential energy functions and including Duschinsky rotation and anharmonicity. PMID:18034464
Excitation of the Yb II transitions terminating on the low-lying odd levels
NASA Astrophysics Data System (ADS)
Smirnov, Yu. M.
2007-10-01
Excitation of the transitions from the even levels of a singly charged ytterbium ion that terminate on the low-lying odd levels 4 f 13(2 F °)6 s 2 2 F °, 4 f 14(1 S)6 p 2 P °, and 4 f 13(2 F °7/2) 5 d6 p(3 D)3[3/2]° is experimentally studied by measuring 51 excitation cross sections at an electron energy of 50 eV, and 16 optical excitation functions are determined within the electron energy range 0 200 eV. The largest magnitudes of the measured cross sections exceed 3 × 10-17 cm2.
Low-lying isovector 2+ valence-shell excitations of 212Po
NASA Astrophysics Data System (ADS)
Kocheva, D.; Rainovski, G.; Jolie, J.; Pietralla, N.; Stahl, C.; Petkov, P.; Blazhev, A.; Hennig, A.; Astier, A.; Braunroth, Th.; Cortés, M. L.; Dewald, A.; Djongolov, M.; Fransen, C.; Gladnishki, K.; Karayonchev, V.; Litzinger, J.; Müller-Gatermann, C.; Scheck, M.; Scholz, Ph.; Stegmann, R.; Thöle, P.; Werner, V.; Witt, W.; Wölk, D.; Van Isacker, P.
2016-01-01
We present the results from an experiment dedicated to search for quadrupole-collective isovector valence-shell excitations, states with so-called mixed proton-neutron symmetry (MSS), of 212Po. This nucleus was studied in an α -transfer reaction. The lifetimes of two short-lived excited states, candidates for the one-phonon MSS, were determined by utilizing the Doppler shift attenuation method. The experimental results are in qualitative agreement with a simple single-j shell model calculation, which, together with the observed lack of quadrupole collectivity, indicates that the isovector nature of low-lying states is a property of the leading single-particle valence shell configuration.
Low-Lying ππ* States of Heteroaromatic Molecules: A Challenge for Excited State Methods.
Prlj, Antonio; Sandoval-Salinas, María Eugenia; Casanova, David; Jacquemin, Denis; Corminboeuf, Clémence
2016-06-14
The description of low-lying ππ* states of linear acenes by standard electronic structure methods is known to be challenging. Here, we broaden the framework of this problem by considering a set of fused heteroaromatic rings and demonstrate that standard electronic structure methods do not provide a balanced description of the two (typically) lowest singlet state (La and Lb) excitations. While the Lb state is highly sensitive to correlation effects, La suffers from the same drawbacks as charge transfer excitations. We show that the comparison between CIS/CIS(D) can serve as a diagnostic for detecting the two problematic excited states. Standard TD-DFT and even its spin-flip variant lead to inaccurate excitation energies and interstate gaps, with only a double hybrid functional performing somewhat better. The complication inherent to a balanced description of these states is so important that even CC2 and ADC(2) do not necessarily match the ADC(3) reference. PMID:27144975
Semirelativistic potential model for low-lying three-gluon glueballs
Mathieu, Vincent; Semay, Claude; Silvestre-Brac, Bernard
2006-09-01
The three-gluon glueball states are studied with the generalization of a semirelativistic potential model giving good results for two-gluon glueballs. The Hamiltonian depends only on 3 parameters fixed on two-gluon glueball spectra: the strong coupling constant, the string tension, and a gluon size which removes singularities in the potential. The Casimir scaling determines the structure of the confinement. Low-lying J{sup PC} states are computed and compared with recent lattice calculations. A good agreement is found for 1{sup --} and 3{sup --} states, but our model predicts a 2{sup --} state much higher in energy than the lattice result. The 0{sup -+} mass is also computed.
Electron-impact excitation of the low-lying electronic states of HCN
NASA Technical Reports Server (NTRS)
Chutjian, A.; Tanaka, H.; Srivastava, S. K.; Wicke, B. G.
1977-01-01
The first study of the low-energy electron-impact excitation of low-lying electronic transitions in the HCN molecule is reported. Measurements were made at incident electron energies of 11.6 and 21.6 eV in the energy-loss range of 3-10 eV, and at scattering angles of 20-130 deg. Inelastic scattering spectra were placed on the absolute cross-section scale by determining first the ratio of inelastic-to-elastic scattering cross sections, and then separately measuring the absolute elastic scattering cross section. Several new electronic transitions are observed which are intrinsically overlapped in the molecule itself. Assignments of these electronic transitions are suggested. These assignments are based on present spectroscopic and cross-sections measurements, high-energy electron scattering spectra, optical absorption spectra, and ab initio molecular orbital calculations.
The fate of water deposited in the low-lying northern plains
NASA Technical Reports Server (NTRS)
Carr, M. H.
1993-01-01
Many large outflow channels terminate in the low-lying northern plains. If the outflow channels formed by running water, as appears likely, then standing bodies of water must have accumulated at the ends of the channels. Most of the observed channels, and hence the bodies of water, are post-Noachian. They formed after the period for which we have the most abundant evidence of climate change. While it has been speculated that the post-Noachian period has experienced large, episodic, climatic excursions, this paper takes the more conservative view that the climatic conditions on Mars, at least from mid-Hesperian onward, were mostly similar to the climatic conditions that prevail in the present epoch. Thus obliquity variations are taken into account, but massive climate changes induced by the floods are considered so improbable that they are ignored.
On the low-lying states of MgO. II
NASA Technical Reports Server (NTRS)
Bauschlicher, C. W., Jr.; Lengsfield, B. H., III; Silver, D. M.; Yarkony, D. R.
1981-01-01
Using a double zeta plus polarization basis set of Slater orbitals, full valence MCSCF (FVMCSCF) calculations were performed for the low-lying states of MgO. For each state the FVMCSCF calculations were used to identify the important configurations which are then used in the MCSCF calculation and subsequently as references in a single and double excitation CI calculation. This approach is found to treat all states equivalently, with the maximum error in the computed transition energies and equilibrium bond lengths of 800/cm and approximately 0.03 A, respectively. The b 3 Sigma + state which has yet to be characterized experimentally is predicted to have a transition energy of approximately 8300/cm and a bond length of 1.79 A. A spectroscopic analysis of the potential curves indicates that their shapes are in quite reasonable agreement with the range of experimental results.
Theoretical Study of the Low-Lying States of MgN+2
NASA Technical Reports Server (NTRS)
Maitre, Philippe; Bauschlicher, Charles W., Jr.; Gross, Anthony R. (Technical Monitor)
1994-01-01
The structure and binding energies of the low-lying states of MgN2+ have been computed at the multireference configuration interaction level of theory. The effect of Mg inner-shell correlation have been included using the core-polarization potential method. The charge-quadrupole interaction results in a linear 2Sigma+ ground state as expected. The excited states can arise from either the interaction of the 2-P state of Mg+ with N2 or from charge transfer states with Mg(sup 2+)N2- bonding character. The lowest lying excited state, 2-B2, is mixture of these two mechanisms, which results in a C2v, geometry with Mg atoms sitting at the N2 bond midpoint. The small barrier in the bending potential exists between this state and the 2-II State which is the lowest lying linear excited state.
Ground and Low-Lying Collective States of Rotating Three-Boson System
NASA Astrophysics Data System (ADS)
Imran, Mohd.; Ahsan, M. A. H.
2016-04-01
The ground and low-lying collective states of a rotating system of N = 3 bosons harmonically confined in quasi-two-dimension and interacting via repulsive finite-range Gaussian potential is studied in weakly to moderately interacting regime. The N-body Hamiltonian matrix is diagonalized in subspaces of quantized total angular momenta 0 ≥ L ≥ 4N to obtain the ground and low-lying eigenstates. Our numerical results show that breathing modes with N-body eigenenergy spacing of 2ħω⊥, known to exist in strictly 2D system with zero-range (δ-function) interaction potential, may as well exist in quasi-2D system with finite-range Gaussian interaction potential. To gain an insight into the many-body states, the von Neumann entropy is calculated as a measure of quantum correlation and the conditional probability distribution is analyzed for the internal structure of the eigenstates. In the rapidly rotating regime the ground state in angular momentum subspaces L = (q/2)N (N ‑ 1) with q = 2, 4 is found to exhibit the anticorrelation structure suggesting that it may variationally be described by a Bose-Laughlin like state. We further observe that the first breathing mode exhibits features similar to the Bose-Laughlin state in having eigenenergy, von Neumann entropy and internal structure independent of interaction for the three-boson system considered here. On the contrary, for eigenstates lying between the Bose-Laughlin like ground state and the first breathing mode, values of eigenenergy, von Neumann entropy and internal structure are found to vary with interaction.
Cluster correlations for low-lying intruder states of 12Be
NASA Astrophysics Data System (ADS)
Ito, M.; Itagaki, N.; Ikeda, K.
2012-01-01
The formation of intruder states in the low-lying states of 12Be=α+α+4N is studied by applying the generalized two-center cluster model, which can optimize the excess neutrons' orbits depending on the α-α distance. The correlation energy for the intruder states is analyzed from the viewpoint of two different pictures based on the cluster structure: the covalent picture around two α clusters and the binary He-cluster picture. In the covalent picture, the binding energy of (π32-)2(σ12+)2, corresponding to ν(0p)4(1s0d)2 in a naive shell model, gains largely owing to the spin-triplet pairing of the 0d-wave neutrons, which is induced by the two-body spin-orbit interaction. The spin-triplet pairing gives rise to the reduction of the kinetic energy and the increase of the attractive spin-orbit interaction for the excess neutrons. As a result of these correlation energies, the ν(0p)4(1s0d)2 configuration becomes dominant in the ground state. In the binary cluster picture, the correlation energy is investigated from the coupled channels among α+8He, 6He+6He, and 5He+7He. The coupling to 5He+7He, which is neglected in usual binary-cluster models, plays an important role for a large reduction of kinetic energy and the formation of a pair of the low-lying 0+ states with a close energy spacing recently observed in experiment. The rotational bands are also discussed from the viewpoint of these two cluster pictures.
Mirmiran, Roya; Squire, Chad; Wassell, Daniel
2015-01-01
A low lying peroneus brevis muscle belly is a rare anomaly. There are few published studies that support presence of this anomaly as an etiology for peroneal tendon tear. However, the association between a low lying peroneus muscle belly (LLMB) and tendon subluxation is not well explored. In this retrospective study, the magnetic resonance imaging (MRI) and intraoperative findings of 50 consecutive patients undergoing a primary peroneal tendon surgery, in a five year period, were assessed. The sensitivity and specificity of MRI, in comparison to intraoperative findings for identifying peroneal tendon disease was investigated. Presence of associated peroneal tendon pathologies in patients with and without LLMB was compared. Sensitivity of MRI was high in identifying peroneal tenosynovitis (81.58%) and tear (85.71%). Although the sensitivity of MRI for detecting a LLMB (3.23%) and tendon subluxation (10.00%) was low, MRI had high specificity at 94.74% and 100%, respectively. Intraoperatively, LLMB was seen in 62.00% of patients with chronic lateral ankle pain and was associated with 64.52% cases of tenosynovitis, 29.03% cases of tendon subluxation, and 80.65% cases of peroneus brevis tendon tear. While presence of a LLMB did not show any statistically significant association with peroneus brevis tendon subluxation, among the 10 patients with intraoperatively observed tendon subluxation, 9 had a concomitant LLMB. More studies with a larger patient population are needed to better study the role of a low lying muscle belly as a mass occupying lesion resulting in peroneal tendon subluxation. PMID:25998478
Plant, Nathaniel G.; Thompson, David M.; Elias, Edwin
2011-01-01
Using Delft3D, a Chandeleur Island model was constructed to examine the sediment-transport patterns and morphodynamic change caused by Hurricane Katrina and similar storm events. The model setup included a coarse Gulf of Mexico domain and a nested finer-resolution Chandeleur Island domain. The finer-resolution domain resolved morphodynamic processes driven by storms and tides. A sensitivity analysis of the simulated morphodynamic response was performed to investigate the effects of variations in surge levels. The Chandeleur morphodynamic model reproduced several important features that matched observed morphodynamic changes. A simulation of bathymetric change driven by storm surge alone (no waves) along the central portion of the Chandeleur Islands showed (1) a general landward retreat and lowering of the island chain and (2) multiple breaches that increased the degree of island dissection. The locations of many of the breaches correspond with the low-lying or narrow sections of the initial bathymetry. The major part of the morphological change occurred prior to the peak of the surge when overtopping of the islands produced a strong water-level gradient and induced significant flow velocities.
Numerical simulation of a low-lying barrier island's morphological response to Hurricane Katrina
Lindemer, C.A.; Plant, N.G.; Puleo, J.A.; Thompson, D.M.; Wamsley, T.V.
2010-01-01
Tropical cyclones that enter or form in the Gulf of Mexico generate storm surge and large waves that impact low-lying coastlines along the Gulf Coast. The Chandeleur Islands, located 161. km east of New Orleans, Louisiana, have endured numerous hurricanes that have passed nearby. Hurricane Katrina (landfall near Waveland MS, 29 Aug 2005) caused dramatic changes to the island elevation and shape. In this paper the predictability of hurricane-induced barrier island erosion and accretion is evaluated using a coupled hydrodynamic and morphodynamic model known as XBeach. Pre- and post-storm island topography was surveyed with an airborne lidar system. Numerical simulations utilized realistic surge and wave conditions determined from larger-scale hydrodynamic models. Simulations included model sensitivity tests with varying grid size and temporal resolutions. Model-predicted bathymetry/topography and post-storm survey data both showed similar patterns of island erosion, such as increased dissection by channels. However, the model under predicted the magnitude of erosion. Potential causes for under prediction include (1) errors in the initial conditions (the initial bathymetry/topography was measured three years prior to Katrina), (2) errors in the forcing conditions (a result of our omission of storms prior to Katrina and/or errors in Katrina storm conditions), and/or (3) physical processes that were omitted from the model (e.g., inclusion of sediment variations and bio-physical processes). ?? 2010.
Low-Lying S-States of Two-Electron Systems
NASA Astrophysics Data System (ADS)
Khan, Md. Abdul
2014-04-01
The energies of the low-lying bound S-states of some two-electron systems (treating them as three-body systems) like negatively charged hydrogen, neutral helium, positively charged-lithium, beryllium, carbon, oxygen, neon, argon and negatively charged muonium and exotic positronium ions have been calculated employing hyperspherical harmonics expansion method. The matrix elements of two-body interactions involve Raynal-Revai coefficients which are particularly essential for the numerical solution of three-body Schrődinger equation when the two-body potentials are other from Coulomb or harmonic. The technique has been applied for to two-electron ions 1H- (Z = 1) to 40Ar16+ (Z = 18), negatively charged-muonium Mu- and exotic positronium ion Ps-(e + e - e -) considering purely Coulomb interaction. The available computer facility restricted reliable calculations up to 28 partial waves (i.e. K m = 28) and energies for higher K m have been obtained by applying an extrapolation scheme suggested by Schneider.
Potential energy curves for the ground and low-lying excited states of CuAg
Alizadeh, Davood; Shayesteh, Alireza E-mail: ashayesteh@ut.ac.ir; Jamshidi, Zahra E-mail: ashayesteh@ut.ac.ir
2014-10-21
The ground and low-lying excited states of heteronuclear diatomic CuAg are examined by multi-reference configuration interaction (MRCI) method. Relativistic effects were treated and probed in two steps. Scalar terms were considered using the spin-free DKH Hamiltonian as a priori and spin-orbit coupling was calculated perturbatively via the spin-orbit terms of the Breit-Pauli Hamiltonian based on MRCI wavefunctions. Potential energy curves of the spin-free states and their corresponding Ω components correlating with the separated atom limits {sup 2}S(Cu) + {sup 2}S(Ag) and {sup 2}D(Cu) + {sup 2}S(Ag) are obtained. The results are in fine agreement with the experimental measurements and tentative conclusions for the ion-pair B0{sup +} state are confirmed by our theoretical calculations. Illustrative results are presented to reveal the relative importance and magnitude of the scalar and spin-orbit effects on the spectroscopic properties of this molecule. Time dependent density functional theory calculations, using the LDA, BLYP, B3LYP, and SAOP functionals have been carried out for CuAg and the accuracy of TD-DFT has been compared with ab initio results.
A theoretical study on low-lying electronic states and spectroscopic properties of PH
NASA Astrophysics Data System (ADS)
Gao, Yufeng; Gao, Tao
2014-01-01
The low-lying electronic states (X3∑-, a1Δ, b1Σ+, A3Π, c1Π and 5∑-) of the PH species correlating with the first three dissociation channels have been investigated at the MRCI + Q/aug-cc-PV5Z level of theory. Accurate adiabatic potential energy curves and spectroscopic constants (Te, Re, ωeχe, ωe, Be, De) of these electronic states have been reported. Effect of the spin-orbit coupling on the A3Π and 5∑- states of the PH has been calculated, which lead to the spin-orbit-induced predissociation of the A3Π state. Electronic transition moment, Einstein coefficients and Franck-Condon factors for the A3Π - X3∑- system have been calculated. Dipole moment functions (μe) and radiative lifetime (τv‧) for the A3Π state has also been determined. The radiative lifetime for A3Π - X3∑- transition is computed and compared with the available data.
The low-lying electronic states of pentacene and their roles in singlet fission.
Zeng, Tao; Hoffmann, Roald; Ananth, Nandini
2014-04-16
We present a detailed study of pentacene monomer and dimer that serves to reconcile extant views of its singlet fission. We obtain the correct ordering of singlet excited-state energy levels in a pentacene molecule (E (S1) < E (D)) from multireference calculations with an appropriate active orbital space and dynamical correlation being incorporated. In order to understand the mechanism of singlet fission in pentacene, we use a well-developed diabatization scheme to characterize the six low-lying singlet states of a pentacene dimer that approximates the unit cell structure of crystalline pentacene. The local, single-excitonic diabats are not directly coupled with the important multiexcitonic state but rather mix through their mutual couplings with one of the charge-transfer configurations. We analyze the mixing of diabats as a function of monomer separation and pentacene rotation. By defining an oscillator strength measure of the coherent population of the multiexcitonic diabat, essential to singlet fission, we find this population can, in principle, be increased by small compression along a specific crystal direction. PMID:24697685
Properties of the low-lying electronic states of phenanthrene: Exact PPP results
Chakrabarti, A.; Ramasesha, S.
1996-10-05
The authors report properties of the exact low-lying states of phenanthrene, its anion and dianion within the Pariser-Parr-Pople (PPP) model. The experimentally known singlet states of the neutral molecule are well reproduced by the model. The intensities for one and two photon absorption to various single states are also in good agreement with experiment. From the bond orders of these states, the authors predict the equilibrium geometries. The relaxation energies of these states, computed from charge-charge correlations and bond orders, are presented. The authors also present results of ring current calculations in the singlet ground state of phenanthrene. The authors have also reported energies, spin densities, bond orders, and relaxation energies of several triplet states and compared then with experiments as well as with other calculations, where available. The fine structure constants D and E, computed in the lowest triplet state, compare well with those obtained from experiments. These properties are also presented for the anions and the dianions. The PPP model in these cases predicts a low-energy (< 1 eV) dipole excitation. 31 refs., 4 figs., 9 tabs.
Low-lying electronic states of LiF molecule with inner electrons correlation
NASA Astrophysics Data System (ADS)
Wan, Ming-jie; Huang, Duo-hui; Yang, Jun-sheng; Cao, Qi-long; Jin, Cheng-guo; Wang, Fan-hou
2015-06-01
The potential energy curves and dipole moments of the low-lying electronic states of LiF molecule are performed by using highly accurate multi-reference configuration interaction with Awcv5z basis sets. 1s, the inner shell of Li is considered as the closed orbit, which is used to characterise the spectroscopic properties of a manifold of singlet and triplet states. 16 electronic states correlate with two lowest dissociation channels Li(2S)+F(2P) and Li(2P)+F(2P) are investigated. Spectroscopic parameters of the ground state X1Σ+ have been evaluated and critically compared with the available experimental values and the other theoretical data. However, spectroscopic parameters of 13Π, 11Δ, 11Σ-, 11Π, 13Σ+, 23Σ+, 13Δ, 13Σ-, 23Π, 21Π, 33Π, 31Π and 33Σ+ states are studied for the first time. These 13 excited states have shallow potential wells, and the dispersion coefficients of these excited states are predicted. In additional, oscillator strengths of excited states at equilibrium distances are also predicted.
Low-lying stepwise paths for ethylene 1,3-dipolar cycloadditions: A DFT study
NASA Astrophysics Data System (ADS)
Kavitha, K.; Venuvanalingam, P.
Ethylene reacts with 1,3-dipoles such as diazomethane, nitrile oxide, and nitrone to give a single adduct and the potential energy surfaces of these reactions were completely surveyed with Density Functional Theory at the B3LYP/6-31G(d) level; B3LYP/6-311+G(d,p), QCISD/6-31G(d) level calculations were performed for comparison. These reactions were found to have one concerted and four stepwise paths and all of them were thoroughly examined. Calculations show that anti and syn approaches in the stepwise paths merge at one point in the potential energy surface and the stepwise processes (i.e., through syn transition states) are low-lying and concerted paths that are in close competition with them. A closer examination of the computed barriers of the reactions of ethylene with the above dipoles, cyclopentadiene, 1,3-butadiene, and allyl anion reveals that there is a mechanistic cross-over from concerted to stepwise path. While the neutral cycloaddition partners prefer a concerted path, the charged partners strongly favor a stepwise path. The dipoles have both concerted and stepwise (syn) paths in close competition. Such a mechanistic cross-over has been induced by the polar influence of the charged species and this change-over in mechanism could not be observed with allene cycloadditions with the same set of partners because allene is strongly biased towards the stepwise mechanism.
Structure and spectroscopic properties of low-lying states of the HOC(O)O radical.
Linguerri, Roberto; Puzzarini, Cristina; Francisco, Joseph S
2016-02-28
The HOC(O)O radical is a product of the reaction of HOCO radicals with oxygen atoms. The present study provides theoretical prediction of critical spectroscopic features of this radical that should aid in its experimental characterization. Energies, structures, rotational constants, and harmonic frequencies are presented for the ground and two low-lying excited electronic states of HOC(O)O. The energies for the Ã(2)A(″)←X̃(2)A(') and B̃(2)A(')←X̃(2)A(') electronic transitions are reported. The band origin of the B̃←X̃ transition of HOC(O)O is predicted to occur in the near infrared region of the spectrum at around 1.5 eV and it is suggested to be the most promising one for observing this radical spectroscopically. The structural and spectroscopic similarities between HOC(O)O and the isoelectronic radical FC(O)O are discussed. The abundance of experimental data on the FC(O)O radical should guide the spectroscopic characterization of HOC(O)O and serve as a benchmark for the structural and spectroscopic parameters obtained from theory. PMID:26931701
Theoretical calculation of low-lying states of NaAr and NaXe
NASA Technical Reports Server (NTRS)
Laskowski, B. C.; Langhoff, S. R.; Stallcop, J. R.
1981-01-01
Potential curves as well as dipole moments and linking transition moments are calculated for the ground X 2 Sigma + and low lying excited A 2 Pi, B 2 Sigma +, C 2 Sigma +, (4) 2 Sigma +, (2) 2 Pi and (1) 2 Delta states of NaAr and NaXe. Calculations are performed using a self-consistent field plus configuration-interaction procedure with the core electrons replaced by an ab initio effective core potential. The potential curves obtained are found to be considerably less repulsive than the semiempirical curves of Pascale and Vandeplanque (1974) and to agree well with existing experimental data, although the binding energies of those states having potential minima due to van der Waals interactions are underestimated. Emission bands are also calculated for the X 2 Sigma + - C 2 Sigma + excimer transitions of NaAr and NaXe using the calculated transition moments and potential curves, and shown to agree well with experiment on the short-wavelength side of the maximum.
Impulsive thermal x-ray emission from a low-lying coronal loop
Liu, Siming; Li, Youping; Fletcher, Lyndsay
2013-06-01
Understanding the relationship among different emission components plays an essential role in the study of particle acceleration and energy conversion in solar flares. In flares where gradual and impulsive emission components can be readily identified, the impulsive emission has been attributed to non-thermal particles. We carry out detailed analysis of Hα and X-ray observations of a GOES class B microflare loop on the solar disk. The impulsive hard X-ray emission, however, is found to be consistent with a hot, quasi-thermal origin, and there is little evidence of emission from chromospheric footpoints, which challenges conventional models of flares and reveals a class of microflares associated with dense loops. Hα observations indicate that the loop lies very low in the solar corona or even in the chromosphere and both emission and absorption materials evolve during the flare. The enhanced Hα emission may very well originate from the photosphere when the low-lying flare loop heats up the underlying chromosphere and reduces the corresponding Hα opacity. These observations may be compared with detailed modeling of flare loops with the internal kink instability, where the mode remains confined in space without apparent change in the global field shape, to uncover the underlying physical processes and to probe the structure of solar atmosphere.
Pauli blocking in the low-lying, low-spin states of {sup 141}Pr
Scheck, M.; Choudry, S. N.; Elhami, E.; McEllistrem, M. T.; Mukhopadhyay, S.; Orce, J. N.; Yates, S. W.
2008-09-15
The low-lying, low-spin levels of {sup 141}Pr were investigated using (n,n{sup '}{gamma}) techniques. Level energies, branching ratios, and tentative spin assignments for more than 100 states, linked by nearly 300 transitions, were obtained from two angular distributions (E{sub n}=2.0 and 3.0 MeV) and an excitation function measurement (E{sub n}=1.5-3.2 MeV). The application of the Doppler-shift attenuation method led to the determination of lifetimes. The obtained spectroscopic data provide insight into the wave functions of the states observed. A detailed analysis of the [2{sub 1}{sup +} x d{sub 5/2}] and [2{sub 1}{sup +} x g{sub 7/2}] multiplets provides the first quantitative evidence for Pauli blocking in a spherical odd-mass nucleus. The unpaired particle is used to probe the microscopic structure of the first 2{sup +} state of the adjacent core nuclei {sup 140}Ce and {sup 142}Nd.
Theoretical studies of the low-lying states of ScO, ScS, VO, and VS
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.
1986-01-01
Bonding in the low-lying states of ScO, ScS, VO, and VS is theoretically studied. Excellent agreement is obtained with experimental spectroscopic constants for the low-lying states of ScO and VO. The results for VS and ScS show that the bonding in the oxides and sulfides is similar, but that the smaller electronegativity in S leads to a smaller ionic component in the bonding. The computed D0 of the sulfides are about 86 percent of the corresponding oxides, and the low-lying excited states are lower in the sulfides than in the corresponding oxides. The CPF method is shown to be an accurate and cost-effective method for obtaining reliable spectroscopic constants for these systems.
Propagation of vector solitons in a quasi-resonant medium with stark deformation of quantum states
Sazonov, S. V.; Ustinov, N. V.
2012-11-15
The nonlinear dynamics of a vector two-component optical pulse propagating in quasi-resonance conditions in a medium of nonsymmetric quantum objects is investigated for Stark splitting of quantum energy levels by an external electric field. We consider the case when the ordinary component of the optical pulse induces {sigma} transitions, while the extraordinary component induces the {pi} transition and shifts the frequencies of the allowed transitions due to the dynamic Stark effect. It is found that under Zakharov-Benney resonance conditions, the propagation of the optical pulse is accompanied by generation of an electromagnetic pulse in the terahertz band and is described by the vector generalization of the nonlinear Yajima-Oikawa system. It is shown that this system (as well as its formal generalization with an arbitrary number of optical components) is integrable by the inverse scattering transformation method. The corresponding Darboux transformations are found for obtaining multisoliton solutions. The influence of transverse effects on the propagation of vector solitons is investigated. The conditions under which transverse dynamics leads to self-focusing (defocusing) of solitons are determined.
Theoretical spectroscopic constants for the low-lying states of the oxides and sulfides of Mo and Tc
NASA Technical Reports Server (NTRS)
Langhoff, Stephen R.; Bauschlicher, Charles W., Jr.; Pettersson, Lars G. M.; Siegbahn, Per E. M.
1989-01-01
Spectroscopic results were determined for the ground and low-lying states of the oxides and sulfides of Mo and Tc, using the single-reference-based modified coupled pair functional method of Ahlrichs et al. (1985) and Chong et al. (1986) and the multireference-based state-averaged CASSCF/MRCI method. Spectroscopic constants, dipole moments, Mulliken populations, and radiative lifetimes were calculated for selected low-lying states of these molecular systems. The spectroscopy of the MoS and TcS molecules was found to be quite analogous to the corresponding oxides.
Generalized Eigenvectors for Resonances in the Friedrichs Model and Their Associated Gamov Vectors
NASA Astrophysics Data System (ADS)
Baumgärtel, Hellmut
A Gelfand triplet for the Hamiltonian H of the Friedrichs model on ℝ with multiplicity space { K}, dim { K}<∞ , is constructed such that exactly the resonances (poles of the inverse of the Livšic-matrix) are (generalized) eigenvalues of H. The corresponding eigen(anti)linear forms are calculated explicitly. Using the wave matrices for the wave (Möller) operators the corresponding eigen(anti)linear forms on the Schwartz space { S} for the unperturbed Hamiltonian H0 are also calculated. It turns out that they are of pure Dirac type and can be characterized by their corresponding Gamov vector λ → k/(ζ0 - λ)-1, ζ0 resonance, k∈ { K}, which is uniquely determined by restriction of { S} to { S} cap { H}+2, where { H}+2 denotes the Hardy space of the upper half-plane. Simultaneously this restriction yields a truncation of the generalized evolution to the well-known decay semigroup for t ≥ 0 of the Toeplitz type on { H}+2. That is: Exactly those pre-Gamov vectors λ → k/(ζ - λ)-1, ζ from the lower half-plane, k in { K}, have an extension to a generalized eigenvector of H if ζ is a resonance and if k is from that subspace of { K} which is uniquely determined by its corresponding Dirac type antilinear form.
Fourier Transform Emission Spectroscopy of the Low-Lying Electronic States of NbN
NASA Astrophysics Data System (ADS)
Ram, R. S.; Bernath, P. F.
2000-06-01
The high-resolution spectrum of NbN has been investigated in emission in the 3000-15 000 cm-1 region using a Fourier transform spectrometer. The bands were excited in a microwave discharge through a mixture of NbCl5 vapor, ∼5 mTorr of N2, and 3 Torr of He. Numerous bands observed in the near-infrared region have been classified into the following transitions: f1Φ-c1Γ, e1Π-a1Δ, C3Π0+-A3Σ-1, C3Π0--A3Σ-1, C3Π1-a1Δ, C3Π1-A3Σ-0, d1Σ+-A3Σ-0, and d1Σ+-b1Σ+. These observations are consistent with the energy level diagram provided by laser excitation and emission spectroscopy [Y. Azuma, G. Huang, M. P. J. Lyne, A. J. Merer, and V. I. Srdanov, J. Chem. Phys. 100, 4138-4155 (1993)]. The missing d1Σ+ state has been observed for the first time and its spectroscopic parameters are consistent with the theoretical predictions of S. R. Langhoff and W. Bauschlicher, Jr. [J. Mol. Spectrosc. 143, 169-179 (1990)]. Rotational analysis of a number of bands has been obtained and improved spectroscopic parameters have been extracted for the low-lying electronic states. The observation of several vibrational bands with v = 1 has enabled us to determine the vibrational intervals and equilibrium bond lengths for the A3Σ-0, a1Δ, b1Σ+, d1Σ+, and C3Π1 states.
Low-lying levels of 76Ge, a candidate for neutrinoless double- β decay
NASA Astrophysics Data System (ADS)
Mukhopadhyay, S.; B. P. Crider Team; E. E. Peters Team; F. M. Prados-Este'vez Team; M. T. McEllistrem Team; S. W. Yates Team
2015-10-01
The low-spin structure of 76Ge was studied at the University of Kentucky with the (n,n' γ) reaction. This nucleus is a parent in double- β decay and is also a rare example of a nucleus to exhibit rigid triaxial deformation in the low-lying states. Excitation function measurements performed with neutrons from 1.6 to 3.7 MeV helped determine the threshold for the γ rays and hence their placement in the level scheme. Lifetimes, spins,multipolarities, and branching ratios were obtained from angular distributions measured at neutron energies of 3.0 and 3.5 MeV. New levels identified around 2 MeV will give insight to the nuclear structure aspects of 76Ge. It is also important to identify any γ rays around 2039 keV, as the experimental signature for neutrinoless double- β decay is a weak peak at this energy. In a recent study with 4.9-MeV neutrons, a reported 2039-keV γ ray from the 3952-keV level was not observed. However, definitely a new level at 3147 keV with 2584- and 2038-keV γ rays to the 21+ and 22+ states, respectively was established. These findings indicate that backgrounds in the search for the neutrinoless double- β decay of 76Ge may be more complex. This material is based upon work supported by the U.S. National Science Foundation under Grant No. PHY-1305801.
Searching for low-lying multi-particle thresholds in lattice spectroscopy
Mahbub, M. Selim; Kamleh, Waseem; Leinweber, Derek B.; Williams, Anthony G.
2014-03-15
We explore the Euclidean-time tails of odd-parity nucleon correlation functions in a search for the S-wave pion–nucleon scattering-state threshold contribution. The analysis is performed using 2+1 flavor 32{sup 3}×64 PACS-CS gauge configurations available via the ILDG. Correlation matrices composed with various levels of fermion source/sink smearing are used to project low-lying states. The consideration of 25,600 fermion propagators reveals the presence of more than one state in what would normally be regarded as an eigenstate-projected correlation function. This observation is in accord with the scenario where the eigenstates contain a strong mixing of single and multi-particle states but only the single particle component has a strong coupling to the interpolating field. Employing a two-exponential fit to the eigenvector-projected correlation function, we are able to confirm the presence of two eigenstates. The lower-lying eigenstate is consistent with a Nπ scattering threshold and has a relatively small coupling to the three-quark interpolating field. We discuss the impact of this small scattering-state contamination in the eigenvector projected correlation function on previous results presented in the literature. -- Highlights: • Correlation-matrix projected correlators reveal more than one state contributing. • Results are associated with strong mixing of single and multi-particle states in QCD. • A two-exponential fit confirms the presence of two QCD eigenstates. •The lower-lying eigenstate is consistent with a nucleon–pion scattering threshold. •The impact of this small contamination on the higher-lying state is examined.
Tricking Landau-Yang: How to obtain the diphoton excess from a vector resonance
NASA Astrophysics Data System (ADS)
Chala, Mikael; Duerr, Michael; Kahlhoefer, Felix; Schmidt-Hoberg, Kai
2016-04-01
We show that contrary to naive expectations the recently observed diphoton excess can be explained by a vector resonance, which decays to a photon and a light scalar s, followed by a decay of the scalar into two photons: Z‧ → γs → 3 γ. As the two photons from the scalar decay are highly boosted, the experimental signature is an apparent diphoton final state. In fact all the necessary ingredients are naturally present in Z‧ models: Additional fermions with electroweak quantum numbers are required in order to render the theory anomaly free and naturally induce the required effective couplings, while the hidden Higgs which gives mass to the Z‧ can be very light. In particular no new coloured states are required in this framework. We also show that in such a setup the width of the resonance can be rather large, while all couplings remain perturbative.
Yoshinaga, N.; Arima, A.
2010-04-15
We propose some new, efficient, and practical extrapolation methods to obtain a few low-lying eigenenergies of a large-dimensional Hamiltonian matrix in the nuclear shell model. We obtain those energies at the desired accuracy by extrapolation after diagonalizing small-dimensional submatrices of the sorted Hamiltonian matrix.
Vector leptoquarks and the 750 GeV diphoton resonance at the LHC
NASA Astrophysics Data System (ADS)
Murphy, Christopher W.
2016-06-01
The ATLAS and CMS Collaborations recently presented evidence of a resonance decaying to pairs of photons around 750 GeV. In addition, the BaBar, Belle, and LHCb Collaborations have evidence of lepton non-universality in the semileptonic decays of B mesons. In this work, we make a first step towards a unified explanation of these anomalies. Specifically, we extend the Standard Model by including vector leptoquarks and a scalar singlet that couples linearly to pairs of the leptoquarks. We find there is parameter space that gives the correct cross section for a putative 750 GeV resonance decaying to photons that is consistent with unitarity, measurements of the properties of the 125 GeV Higgs boson, and direct searches for resonances in other channels. In addition, we also show that constraints can be derived on any Beyond the Standard Model explanation of the 750 GeV resonance where the only new particles are scalars, which are strong enough to rule out certain types of models entirely.
Novel triaxial structure in low-lying states of neutron-rich nuclei around A ≈100
NASA Astrophysics Data System (ADS)
Xiang, J.; Yao, J. M.; Fu, Y.; Wang, Z. H.; Li, Z. P.; Long, W. H.
2016-05-01
Background: In recent years, the study of triaxiality in the low-lying states of atomic nuclei with transition character or shape coexistence has been of great interest. Previous studies indicate that the neutron-rich nuclei in the A ˜100 mass region with Z ˜40 ,N ˜60 serve as good grounds for examining the role of triaxiality in nuclear low-lying states. Purpose: The aim of this work is to provide a microscopic study of low-lying states for nuclei in the A ˜100 mass regions and to examine in detail the role of triaxiality in the shape-coexistence phenomena and the variation of shape with the isospin and spin values at the beyond mean-field level. Method: The starting point of our method is a set of relativistic mean-field plus BCS wave functions generated with a constraint on triaxial deformations (β ,γ ) . The excitation energies and electric multipole transition strengths of low-lying states are calculated by solving a five-dimensional collective Hamiltonian (5DCH) with parameters determined by the mean-field wave functions. Results: The low-lying states of Mo isotopes and of N =60 isotones in the A ˜100 mass region are calculated. The results indicate that triaxiality is essential to reproduce the data of excitation energies and electric quadrupole transition strengths in low-lying states and plays an important role in the shape evolution as a function of nucleon number. However, the decrease of nuclear collectivity with the increase of angular momentum in neutron-rich Mo isotopes has not been reproduced. Conclusions: The evolution of nuclear collectivity in the low-lying states of neutron-rich nuclei in the A ˜100 mass region as a function of nucleon number is governed by the novel triaxial structure. However, the mechanism that governs the variation of nuclear shape with spin in Mo isotopes remains unclear and deserves further investigation by taking into account the effects other than the collective motions.
Sea Level Rise Enhanced Halocarbon Production in Low-lying Coastal Ecosystem in the Southeastern US
NASA Astrophysics Data System (ADS)
Chow, A. T.; Conner, W.; Williams, T.; Song, B.
2010-12-01
Saltwater tides bring high concentrations of chloride and bromide inland where it mixes with terrestrial humic substances from surrounding forested watersheds and ferric/ferrous ions from shallow groundwater. With all the essential precursors (i.e., chloride, bromide, and humic substances) and catalysts (ferric/ferrous ions with sunlight), low-lying coastal ecosystems could be a hotspot for halocarbon formation. Fluctuating water levels and salinity due to the tidal cycle alter both redox reactions and water chemistry, influencing the formation and fate of halocarbons. A controlled study was conducted to confirm the abiotic formation of trihalomethanes (THMs) by the photo-Fenton reaction and the effects of the precursors on their formation. Four THM species, including chloroform (CHCl3), bromodichloromethane (CHBrCl2), dibromochloromethane (CHBr2Cl), and bromoform (CHBr3), were examined. Sets of aqueous solutions were prepared using filtered Waccamaw River samples and synthesized NaCl / NaBr, and Fe2(SO4)3 and H2O2 solutions. Solutions were enclosed in quartz tubes and exposed for 7 days to natural sunlight. Although total THM formation increased with DOC concentration, the reactivity of C in forming THM was relatively consistent across DOC concentrations, with an average of 2.6 nmol-THM mmol-C-1. The reactivity in forming THMs through the photo-Fenton reaction was significantly lower than that in chlorinated water. Reactivity generally ranged from 3-20 mmol-THM mol-C-1. The differences in reactivity suggested that greater yield of THMs could be produced under the right reaction condition. In particular, the study showed that bromide increases the reactivity of DOC in forming THMs and enhances the formation of brominated THMs. The bromine substitution factor in the NaCl treatment ranged from 19 to 24% but increased to 43 and 46% when NaBr was added. Results suggest that increased salinity and bromide concentration in saltwater-impacted coastal ecosystems could
Taming the low-lying electronic states of FeH.
DeYonker, Nathan J; Allen, Wesley D
2012-12-21
The low-lying electronic states (X (4)Δ, A (4)Π, a (6)Δ, b (6)Π) of the iron monohydride radical, which are especially troublesome for electronic structure theory, have been successfully described using a focal point analysis (FPA) approach that conjoined a correlation-consistent family of basis sets up to aug-cc-pwCV5Z-DK with high-order coupled cluster theory through hextuple (CCSDTQPH) excitations. Adiabatic excitation energies (T(0)) and spectroscopic constants (r(e), r(0), B(e), B(0), D(e), ω(e), v(0), α(e), ω(e)x(e)) were extrapolated to the valence complete basis set Douglas-Kroll (DK) aug-cc-pwCV∞Z-DK CCSDT level of theory, and additional treatments accounted for higher-order valence electron correlation, core correlation, spin-orbit coupling, and the diagonal Born-Oppenheimer correction. The purely ab initio FPA approach yields the following T(0) results (in eV) for the lowest spin-orbit components of each electronic state: 0 (X (4)Δ) < 0.132 (A (4)Π) < 0.190 (a (6)Δ) < 0.444 (b (6)Π). The computed anharmonic fundamental vibrational frequencies (v(0)) for the (4,6)Δ electronic states are within 3 cm(-1) of experiment and provide reliable predictions for the (4,6)Π states. With the cc-pVDZ basis set, even CCSDTQPH energies give an incorrect ground state of FeH, highlighting the importance of combining high-order electron correlation treatments with robust basis sets when studying transition-metal radicals. The FPA computations provide D(0) = 1.86 eV (42.9 kcal mol(-1)) for the 0 K dissociation energy of FeH and Δ(f)H(298) (∘) [FeH((g))] = 107.7 kcal mol(-1) for the enthalpy of formation at room temperature. Despite sizable multireference character in the quartet states, high-order single-reference coupled cluster computations improve the spectroscopic parameters over previous multireference theoretical studies; for example, the X (4)Δ → A (4)Π and a (6)Δ → b (6)Π transition energies are reproduced to 0
NASA Astrophysics Data System (ADS)
Zhang, Guojun; Zhao, Peng; Zhang, Wendong
2015-04-01
The MEMS vector hydrophone developed by the North University of China has advantages of high Signal to Noise Ratio, ease of array integration, etc. However, the resonance frequency of the MEMS device in the liquid is different from that in the air due to the fluid-structure interaction (FSI). Based on the theory of Fluid-Solid Coupling, a generalized distributed mass attached on the micro-structure has been found, which results in the resonance frequency of the microstructure in the liquid being lower than that in the air. Then, an FSI simulation was conducted by ANSYS software. Finally, the hydrophone was measured by using a shaking table and a vector hydrophone calibration system respectively. Results show that, due to the FSI, the resonance frequency of the MEMS devices of the bionic vector hydrophone in the liquid declines approximately 30% compared to the case in the air.
The water budget of a coastal low-lying wetland area at the German Baltic Coast
NASA Astrophysics Data System (ADS)
Bronstert, Axel; Graeff, Thomas; Selle, Benny; Salzmann, Thomas; Franck, Christian; Miegel, Konrad
2016-04-01
that despite low slope, sandy soils and forest vegetation, the catchment's hydrology is dominated by quick discharge components, for which the near-surface groundwater and the reaction for open water surfaces are the main cause. The seasonality of the area's discharge is characterized by the formation of quick discharge components mainly during the winter half-year, and by the retention effect of the lowland/fen. This retention is especially high in summer, when the surface and ground water levels have decreased due to high evaporation rates and the discharge out of the area may cease. The magnitude of the area's outflow thus generally depends on the catchment's water level. Due to the possible backlog of surface water caused by high water levels of the Baltic Sea, the direction of flow may reverse episodically. In the subareas between the trenches of the lowland, vertical exchange processes from precipitation and evaporation dominate. The lateral sub-surface interaction from/to the Baltic Sea is rather small due to the particular low local subsurface hydraulic conductivity and the very small hydraulic gradient. In summary, it can be said that this coastal low-lying wetland in the restoration phase shows rather heterogeneous hydrological processes and water balance. Characteristic are the high relevance of the subsurface processes and a strong seasonal variation, i.e. very low discharge rates in summer (except for summer convective rain storms) and considerable discharge rates in winter. The anthropogenic interventions in those coastal areas during the last two centuries have changed their water balance exceedingly. The interaction with the Baltic Sea via groundwater exchange under the dunes is very small.
Das, Mousumi
2014-03-28
We studied the nature of the ground state and low-lying excited states of armchair polyacene oligomers (Polyphenanthrene) within long-range Pariser-Parr-Pople model Hamiltonian with up to 14 monomers using symmetrized density matrix renormalization group technique. The ground state of all armchair polyacenes studied is found to be singlet. The results show that lowest singlet dipole allowed excited state has higher energy for armchair polyacenes as compared to linear fused polyacenes. Moreover, unlike linear fused polyacenes, the lowest singlet excited state of these oligomers is always found to lie below the lowest dipole forbidden two-photon state indicating that these armchair polyacene oligomers strongly fluoresce. The calculations of low-lying excitations on singly and triply electron doped armchair polyacene oligomers show a low energy band with strong transition dipole moment that coupled to charge conductivity. This implies armchair polyacene posses novel field-effect transistor properties. PMID:24697451
Das, Mousumi
2014-03-28
We studied the nature of the ground state and low-lying excited states of armchair polyacene oligomers (Polyphenanthrene) within long-range Pariser-Parr-Pople model Hamiltonian with up to 14 monomers using symmetrized density matrix renormalization group technique. The ground state of all armchair polyacenes studied is found to be singlet. The results show that lowest singlet dipole allowed excited state has higher energy for armchair polyacenes as compared to linear fused polyacenes. Moreover, unlike linear fused polyacenes, the lowest singlet excited state of these oligomers is always found to lie below the lowest dipole forbidden two-photon state indicating that these armchair polyacene oligomers strongly fluoresce. The calculations of low-lying excitations on singly and triply electron doped armchair polyacene oligomers show a low energy band with strong transition dipole moment that coupled to charge conductivity. This implies armchair polyacene posses novel field-effect transistor properties.
Dixit, Gopal; Majumder, Sonjoy; Sahoo, Bijaya K.; Chaudhuri, Rajat K.
2007-10-15
We report electric quadrupole (E2) and magnetic dipole (M1) transition amplitudes of the first few low-lying states of quadruply ionized vanadium (V{sup 4+}), which are important in various experimental applications and astrophysics. To our knowledge, most of these presented results are determined for the first time in the literature. A relativistic multireference Fock-space coupled-cluster theory with single (S), double (D), and partial triple (T) excitations is employed to compute the forbidden transition probabilities and lifetimes of the low-lying states in V{sup 4+}. Estimations of different correlation effects arising through the above formalism have been highlighted by investigating core and valence electron excitations. A long lifetime is found for the first excited 3d {sup 2}D{sub 5/2} state, which suggests that V{sup 4+} may be one of the useful candidates for many important studies.
NASA Technical Reports Server (NTRS)
Langhoff, Stephen R.; Pettersson, Lars G. M.; Bauschlicher, Charles W., Jr.; Partridge, Harry
1987-01-01
A systematic analysis of the low-lying states of all of the second-row transition metal (TM) hydrides except CdH is reported. The calculations included the dominant relativistic contributions through the use of the relativistic effective core potentials of Hay and Wadt (1985). Electron correlation was incorporated, using single-plus-double configuration interaction, the coupled pair functional (CPF) formalism of Ahlrichs et al. (1985), and the Chong and Langhoff (1986) modified version of the CPF method. The spectroscopic parameters D(e), r(e), and mu(e) determined for the low-lying states are compared with the available experimental data and previous theoretical results. In contrast to the first-row TM hydrides studied earlier (Chong et al., 1986), the spectroscopic constants for the second-row TM hydrides were found to be much less sensitive to the level of correlation treatment.
Impact of the electron environment on the lifetime of the {sup 229}Th{sup m} low-lying isomer
Karpeshin, F. F.; Trzhaskovskaya, M. B.
2007-11-15
The question of the lifetime of the {sup 229}Th{sup m} low-lying isomer is considered in light of current experimental research. A strong effect of the electron shell on lifetime is demonstrated, depending on the energy of the isomer. Calculations are performed within the framework of the multiconfiguration Dirac-Fock method. The calculated lifetime ranges from around 1 min down to 10{sup -5} s. Prospects for further experimental research of the isomer are discussed.
Rajesh Sharma, R.; Marikkannu, P.
2015-01-01
A novel hybrid approach for the identification of brain regions using magnetic resonance images accountable for brain tumor is presented in this paper. Classification of medical images is substantial in both clinical and research areas. Magnetic resonance imaging (MRI) modality outperforms towards diagnosing brain abnormalities like brain tumor, multiple sclerosis, hemorrhage, and many more. The primary objective of this work is to propose a three-dimensional (3D) novel brain tumor classification model using MRI images with both micro- and macroscale textures designed to differentiate the MRI of brain under two classes of lesion, benign and malignant. The design approach was initially preprocessed using 3D Gaussian filter. Based on VOI (volume of interest) of the image, features were extracted using 3D volumetric Square Centroid Lines Gray Level Distribution Method (SCLGM) along with 3D run length and cooccurrence matrix. The optimal features are selected using the proposed refined gravitational search algorithm (RGSA). Support vector machines, over backpropagation network, and k-nearest neighbor are used to evaluate the goodness of classifier approach. The preliminary evaluation of the system is performed using 320 real-time brain MRI images. The system is trained and tested by using a leave-one-case-out method. The performance of the classifier is tested using the receiver operating characteristic curve of 0.986 (±002). The experimental results demonstrate the systematic and efficient feature extraction and feature selection algorithm to the performance of state-of-the-art feature classification methods. PMID:26509188
Blum, H; Salerno, J C; Prince, R C; Leigh, J S; Ohnishi, T
1977-01-01
The temperature dependence of the EPR spectrum of oxidized high-potential iron protein from Chromatium vinosum has been studied. From line width and intensity measurements it is possible to determine the position of the first excited unoccupied state, 160 +/- 10 cm-1 above the ground state orbital. PMID:198036
Evaluating the 100 year floodplain as an indicator of flood risk in low-lying coastal watersheds
NASA Astrophysics Data System (ADS)
Sebastian, A.; Brody, S.; Bedient, P. B.
2013-12-01
The Gulf of Mexico is the fastest growing region in the United States. Since 1960, the number of housing units built in the low-lying coastal counties has increased by 246%. The region experiences some of the most intense rainfall events in the country and coastal watersheds are prone to severe flooding characterized by wide floodplains and ponding. This flooding is further exacerbated as urban development encroaches on existing streams and waterways. While the 100 year floodplain should play an important role in our ability to develop disaster resilient communities, recent research has indicated that existing floodplain delineations are a poor indicator of actual flood losses in low-lying coastal regions. Between 2001 and 2005, more than 30% of insurance claims made to FEMA in the Gulf Coast region were outside of the 100 year floodplain and residential losses amounted to more than $19.3 billion. As population density and investments in this region continue to increase, addressing flood risk in coastal communities should become a priority for engineers, urban planners, and decision makers. This study compares the effectiveness of 1-D and a 2-D modeling approaches to spatially capture flood claims from historical events. Initial results indicate that 2-D models perform much better in coastal environments and may serve better for floodplain modeling helping to prevent unintended losses. The results of this study encourage a shift towards better engineering practices using existing 2-D models in order to protect resources and provide guidance for urban development in low-lying coastal regions.
Hauschild, K.; Bernstein, L.A.; Becker, J.A.
1996-12-31
The observation of one-step `primary` gamma-ray transitions directly linking the superdeformed (SD) states to the normal deformed (ND) low-lying states of known excitation energies (E{sub x}), spins and parities (J{sup {pi}}) is crucial to determining the E{sub x} and J{sup {pi}} of the SD states. With this knowledge one can begin to address some of the outstanding problems associated with SD nuclei, such as the identical band issue, and one can also place more stringent restrictions on theoretical calculations which predict SD states and their properties. Brinkman, et al., used the early implementation of the GAMMASPHERE spectrometer array (32 detectors) and proposed a single, candidate {gamma} ray linking the {sup 194}Pb yrast SD band to the low-lying ND states in {sup 194}Pb. Using 55 detectors in the GAMMASPHERE array Khoo, et al., observed multiple links between the yrast SD band in {sup 194}Hg and the low-lying level scheme and conclusively determined E{sub x} and J of the yrast SD states. Here the authors report on an experiment in which Gammasphere with 88 detectors was used and the E{sub x} and J{sup {pi}} values of the yrast SD states in {sup 194}Pb were uniquely determined. Twelve one-step linking transitions between the yrast SD band and low-lying states in {sup 194}Pb have been identified, including the transition proposed by Brinkman. These transitions have been placed in the level scheme of {sup 194}Pb using coincidence relationships and agreements between the energies of the primary transitions and the energy differences in level spacings. Furthermore, measurements of angular asymmetries have yielded the multipolarities of the primaries which have allowed J{sup {pi}} assignments of the {sup 194}Pb SD states to be unambiguously determined for the first time without a priori assumptions about the character of SD bands. A study performed in parallel to this work using the EUROGAM-II array reports similar, but somewhat less extensive, results.
Sharma, Neetika; Dahiya, Harleen; Chatley, P. K.; Gupta, Manmohan
2010-04-01
Magnetic moments of the low lying and charmed spin (1/2){sup +} and spin (3/2){sup +} baryons have been calculated in the SU(4) chiral constituent quark model ({chi}CQM) by including the contribution from cc fluctuations. Explicit calculations have been carried out for the contribution coming from the valence quarks, ''quark sea'' polarizations and their orbital angular momentum. The implications of such a model have also been studied for magnetic moments of the low lying spin (3/2){sup +{yields}}(1/2){sup +} and (1/2){sup +{yields}}(1/2){sup +} transitions as well as the transitions involving charmed baryons. The predictions of {chi}CQM not only give a satisfactory fit for the baryons where experimental data is available but also show improvement over the other models. In particular, for the case of {mu}(p), {mu}({Sigma}{sup +}), {mu}({Xi}{sup 0}), {mu}({Lambda}), Coleman-Glashow sum rule for the low lying spin (1/2){sup +} baryons and {mu}({Delta}{sup +}), {mu}({Omega}{sup -}) for the low lying spin (3/2){sup +} baryons, we are able to achieve an excellent agreement with data. For the spin (1/2){sup +} and spin (3/2){sup +} charmed baryon magnetic moments, our results are consistent with the predictions of the QCD sum rules, light cone sum rules and spectral sum rules. For the cases where light quarks dominate in the valence structure, the sea and orbital contributions are found to be fairly significant however, they cancel in the right direction to give the correct magnitude of the total magnetic moment. On the other hand, when there is an excess of heavy quarks, the contribution of the quark sea is almost negligible, for example, {mu}({Omega}{sub c}{sup 0}), {mu}({Lambda}{sub c}{sup +}), {mu}({Xi}{sub c}{sup +}), {mu}({Xi}{sub c}{sup 0}), {mu}({Omega}{sub cc}{sup +}), {mu}({Omega}{sup -}), {mu}({Omega}{sub c}*{sup 0}), {mu}({Omega}{sub cc}*{sup +}), and {mu}({Omega}{sub ccc}*{sup ++}). The effects of configuration mixing and quark masses have also been
Vibronic effects on the low-lying electronic excitations in N2O induced by electron impact
NASA Astrophysics Data System (ADS)
Watanabe, Noboru; Takahashi, Masahiko
2014-08-01
We report a theoretical study on the valence-shell electronic excitations of N2O induced by electron impact. Momentum transfer-dependent generalized oscillator strengths (GOSs) or GOS profiles have been calculated for the low-lying electronic excitations using theoretical wave functions at the equation-of-motion coupled-cluster singles and doubles level. In the calculation, Herzberg-Teller vibronic effects are taken into account. The computed results are in overall agreement with experimental GOS profiles reported in the literature and reveal prominent roles of the bending vibration of N2O in the B1Δ and C1Π transitions.
On the low-lying states of WO - A comparison with CrO and MoO
NASA Technical Reports Server (NTRS)
Nelin, C. J.; Bauschlicher, C. W., Jr.
1985-01-01
The four low-lying states of WO were investigated and compared with similar states of CrO and MoO. For all these systems the ground state is 5 Pi, but the ordering of the upper states is different between WO and either CrO or MoO. The difference in the state ordering arises in part from the fact that in WO all of the states are formed from W(+) in a d4S1 configuration, whereas in both CrO and MoO some states are formed from the d5 configuration and others from the d4S1 configuration.
Discovery of low-lying E1 and M1 strengths in {sup 232}Th
Adekola, A. S.; Hammond, S. L.; Hill, A.; Karwowski, H. J.; Angell, C. T.; Howell, C. R.; Kwan, E.; Kelley, J. H.
2011-03-15
Properties of low-energy dipole states in {sup 232}Th have been investigated with the nuclear resonance fluorescence technique. The present work used monoenergetic {gamma}-ray beams at energies of 2-4 MeV from the high-intensity {gamma}-ray source at Triangle Universities Nuclear Laboratory. Over 40 transitions corresponding to deexcitation to the ground state and first excited state were observed for the first time. Excitation energies, integrated cross sections, decay widths, branching ratios, and transition strengths for those states in {sup 232}Th were determined and compared with quasiparticle random-phase-approximation calculations. A large number of E1 transitions were observed for the first time in actinide nuclei with summed strength of 3.28(69)x10{sup -3} e{sup 2} fm{sup 2}. The observed summed M1 strength of 4.26(63){mu}{sub N}{sup 2} is in good agreement with the other actinides and with the systematics of the scissors mode in deformed rare-earth nuclei.
Ab initio study of the low lying electronic states of ZnF and ZnF-.
Hayashi, Shinsuke; Léonard, Céline; Chambaud, Gilberte
2008-07-28
Highly correlated ab initio calculations have been performed for an accurate determination of the electronic structure and of the spectroscopy of the low lying electronic states of the ZnF system. Using effective core pseudopotentials and aug-cc-pVQZ basis sets for both atoms, the potential curves, the dipole moment functions, and the transition dipole moments between relevant electronic states have been calculated at the multireference-configuration-interaction level. The spectroscopic constants calculated for the X(2)Sigma(+) ground state are in good agreement with the most recent theoretical and experimental values. It is shown that, besides the X(2)Sigma(+) ground state, the B(2)Sigma(+), the C(2)Pi, and the D(2)Sigma(+) states are bound. The A(2)Pi state, which has been mentioned in previous works, is not bound but its potential presents a shoulder in the Franck-Condon region of the X(2)Sigma(+) ground state. All of the low lying quartet states are found to be repulsive. The absorption transitions from the v=0 level of the X(2)Sigma(+) ground state toward the three bound states have been evaluated and the spectra are presented. The potential energy of the ZnF(-) molecular anion has been determined in the vicinity of its equilibrium geometry and the electronic affinity of ZnF (EA=1.843 eV with the zero energy point correction) has been calculated in agreement with the photoelectron spectroscopy experiments. PMID:18681652
NASA Astrophysics Data System (ADS)
Kerkines, Ioannis S. K.; Mavridis, Aristides
2004-01-01
The ground and low-lying states of the monopositive vanadium and chromium carbides, VC+ and CrC+ have been studied by multireference methods and quantitative basis sets. Potential energy curves for 17 (VC+) and 19 (CrC+) states have been fully calculated. A variety of binding modes is revealed in the low-lying spectrum of the two molecular cations, often accompanied with an electronic charge transfer from the metal cation towards carbon. Two states compete for the ground state identity in both systems. One state comprises two π and ½σ bonds (similarly to ScC+ and TiC+), while the other state forms a genuine triple bond. After a rather intricate analysis including core electron effects, scalar relativity and curve shifts, the formal ground states of VC+ and CrC+ are found to be of 3Δ and 2Δ symmetry, with estimated energy differences from the competing 1Σ+ and 4Σ- states of 1-3 and 3-7 kcal/mol, respectively. At the highest level of theory including core/valence correlation and one-electron relativistic effects, the calculated ground-state binding energies are in satisfactory agreement with available experimental values.
Algebraic approach to the structure of the low-lying states in A ≈100 Ru isotopes
NASA Astrophysics Data System (ADS)
Kisyov, S.; Bucurescu, D.; Jolie, J.; Lalkovski, S.
2016-04-01
The structure of the low-lying states in the odd- and even-mass A ≈100 Ru isotopes is studied in the framework of two algebraic models. The even-mass Ru nuclei are first described within the interacting boson model 1 (IBM-1). The output of these calculations was then used to calculate the odd-A isotopes within the interacting boson-fermion model 1 (IBFM-1), where a coupling of the odd neutron to the even-even core is considered. The level energies and transition probabilities calculated in the present work are tested against the experimental data. One-nucleon transfer spectroscopic factors as well as electromagnetic moments were also calculated for the odd-A Ru and compared to the experimental values. The transitional character of the isotopes is studied. Most of the low-lying positive-parity states in the odd-A Ru nuclei below 2 MeV are interpreted on the basis of ν d5 /2 and ν g7 /2 configurations. The role of the ν s1 /2 orbital in the nuclear structure of the odd-mass Ru nuclei at low energies is also studied. The negative-parity states are interpreted as ν h11 /2 excitations coupled to the core. The evolution of the IBM-1 and IBFM-1 parameters is discussed.
Low-lying spectra of {sup 9}{Lambda}Be and {sup 9}Be within three-cluster model
Filikhin, I.; Suslov, V. M.; Vlahovic, B.
2011-10-24
An {alpha}-cluster model is applied to study the low-lying spectra of the {sup 9}{Lambda}Be and {sup 9}Be nuclei. The {alpha}{alpha}{Lambda} and {alpha}{alpha}n three-body problems are numerically solved by the Faddeev equations in configuration space using phenomenological pair potentials with spin-orbital {alpha}{Lambda} and {alpha}n interactions taken into account. For the {sup 9}{Lambda}Be hypernucleus we found a set of the potentials that reproduces the experimental data for the ground state (1/2 {sup +}) binding energy and excitation energy of the 5/2{sup +} and 3/2 {sup +} states, simultaneously. The LS coupling scheme is used for partial wave analysis. The total orbital momentum is fixed for each energy level. Under this assumption we calculated the {sup 9}Be spectrum within {alpha}{alpha}n model. The experiential data are well reproduced by the model, when a new classification for low-lying levels of {sup 9}Be as members of spin-flip doublets is applied.
Strong Electron-Phonon Coupling Superconductivity Induced by a Low-Lying Phonon in IrGe
Hirai, Daigorou; Ali, Mazhar N.; Cava, Robert J.
2014-02-26
The physical properties of the previously reported superconductor IrGe and the Rh_{1-x}Ir_{x}Ge solid solution are investigated. IrGe has an exceptionally high superconducting transition temperature (T_{c}=4.7 K) among the isostructural 1:1 late-metal germanides MGe (M=Rh, Pd, Ir, and Pt). Specific-heat measurements reveal that IrGe has an anomalously low Debye temperature, originating from a low-lying phonon, compared to the other MGe phases. A large jump at T_{c} in the specific-heat data clearly indicates that IrGe is a strong coupling superconductor. In the Rh_{1-x}Ir_{x}Ge solid solution, a relationship between an anomalous change in lattice constants and the Debye temperature is observed. We conclude that the unusually high T_{c} for IrGe is likely due to strong electron–phonon coupling derived from the presence of a low-lying phonon.
An investigation into low-lying electronic states of HCS{sub 2} via threshold photoelectron imaging
Qin, Zhengbo; Cong, Ran; Liu, Zhiling; Xie, Hua; Tang, Zichao E-mail: fanhj@dicp.ac.cn; Fan, Hongjun E-mail: fanhj@dicp.ac.cn
2014-06-07
Low-energy photoelectron imaging spectra of HCS{sub 2}{sup −} are reported for the first time. Vibrationally resolved photodetachment transitions from the ground state of HCS{sub 2}{sup −} to the ground state and low-lying excited states of HCS{sub 2} are observed. Combined with the ab intio calculations and Franck-Condon simulations, well-resolved vibrational spectra demonstrate definitive evidence for the resolution of the ground-state and excited states of HCS{sub 2} radical in the gaseous phase. The ground state and two low-lying excited states of HCS{sub 2} radical are assigned as {sup 2}B{sub 2}, {sup 2}A{sub 2}, and {sup 2}A{sub 1} states, respectively. The adiabatic electron affinity is determined to be 2.910 ± 0.007 eV. And the term energies of the excited states, T{sub 0} = 0.451 ± 0.009 eV and 0.553 ± 0.009 eV, are directly measured from the experimental data, respectively. Angular filtering photoelectron spectra are carried out to assist in the spectral band assignment.
Experimental study of the low-lying structure of {sup 94}Zr with the (n,n{sup '}{gamma}) reaction
Elhami, E.; Orce, J. N.; Scheck, M.; Mukhopadhyay, S.; Choudry, S. N.; McEllistrem, M. T.; Yates, S. W.; Angell, C.; Boswell, M.; Karwowski, H. J.; Fallin, B.; Howell, C. R.; Hutcheson, A.; Parpottas, Y.; Tonchev, A. P.; Tornow, W.; Kelley, J. H.
2008-12-15
The low-lying structure of {sub 40}{sup 94}Zr was studied with the (n,n{sup '}{gamma}) reaction, and a level scheme was established based on excitation function and {gamma}{gamma} coincidence measurements. Branching ratios, multipole mixing ratios, and spin assignments were determined from angular distribution measurements. Lifetimes of levels up to 3.4 MeV were measured by the Doppler-shift attenuation method, and for many transitions the reduced transition probabilities were determined. In addition to the anomalous 2{sub 2}{sup +} state, which has a larger B(E2;2{sub 2}{sup +}{yields}0{sub 1}{sup +}) value than the B(E2;2{sub 1}{sup +}{yields}0{sub 1}{sup +}), the experimental results revealed interesting and unusual properties of the low-lying states in {sup 94}Zr. In a simple interpretation, the excited states are classified in two distinct categories, i.e., those populating the 2{sub 2}{sup +} state and those decaying to the 2{sub 1}{sup +} state.
Gambacurta, D.; Catara, F.
2011-09-15
Low-energy dipole excitations are analyzed for the stable isotopes {sup 40}Ca and {sup 48}Ca in the framework of the Skyrme-second random-phase approximation. The corresponding random-phase approximation calculations provide a negligible strength distribution for both nuclei in the energy region from 5 to 10 MeV. The inclusion and the coupling of 2 particle-2 hole configurations in the second random-phase approximation lead to an appreciable dipole response at low energies for the neutron-rich nucleus {sup 48}Ca. The presence of a neutron skin in the nucleus {sup 48}Ca would suggest the interpretation of the low-lying response in terms of a pygmy excitation. The composition of the excitation modes (content of 1 particle-1 hole and 2 particle-2 hole configurations), their transition densities and their collectivity (number and coherence of the different contributions) are analyzed. This analysis indicates that, in general, these excitations cannot be clearly interpreted in terms of oscillations of the neutron skin against the core with the exception of the peak with the largest B(E1) value, which is located at 9.09 MeV. For this peak the neutron transition density dominates and the neutron and proton transition densities oscillate out of phase in the internal part of the nucleus leading to a strong mixing of isoscalar and isovector components. Therefore, this state shows some features usually associated to pygmy resonances.
Low-lying excited states and nonradiative processes of 9-methyl-2-aminopurine
Trachsel, Maria A.; Lobsiger, Simon; Schär, Tobias; Leutwyler, Samuel
2014-01-28
The UV spectrum of the adenine analogue 9-methyl-2-aminopurine (9M-2AP) is investigated with one- and two-color resonant two-photon ionization spectroscopy at 0.3 and 0.05 cm{sup −1} resolution in a supersonic jet. The electronic origin at 32 252 cm{sup −1} exhibits methyl torsional subbands that originate from the 0A{sub 1}{sup ′′} (l = 0) and 1E{sup ″} (l = ±1) torsional levels. These and further torsional bands that appear up to 0{sub 0}{sup 0}+230 cm{sup −1} allow to fit the threefold (V{sub 3}) barriers of the torsional potentials as |V{sub 3}{sup ′′}|=50 cm{sup −1} in the S{sub 0} and |V{sub 3}{sup ′}|=126 cm{sup −1} in the S{sub 1} state. Using the B3LYP density functional and correlated approximate second-order coupled cluster CC2 methods, the methyl orientation is calculated to be symmetric relative to the 2AP plane in both states, with barriers of V{sub 3}{sup ′′}=20 cm{sup −1} and V{sub 3}{sup ′}=115 cm{sup −1}. The 0{sub 0}{sup 0} rotational band contour is 75% in-plane (a/b) polarized, characteristic for a dominantly long-axis {sup 1}ππ{sup *} excitation. The residual 25% c-axis polarization may indicate coupling of the {sup 1}ππ{sup *} to the close-lying {sup 1}nπ{sup *} state, calculated at 4.00 and 4.01 eV with the CC2 method. However, the CC2 calculated {sup 1}nπ oscillator strength is only 6% of that of the {sup 1}ππ{sup *} transition. The {sup 1}ππ{sup *} vibronic spectrum is very complex, showing about 40 bands within the lowest 500 cm{sup −1}. The methyl torsion and the low-frequency out-of-plane ν{sub 1}{sup ′} and ν{sub 2}{sup ′} vibrations are strongly coupled in the {sup 1}ππ{sup *} state. This gives rise to many torsion-vibration combination bands built on out-of-plane fundamentals, which are without precedence in the {sup 1}ππ{sup *} spectrum of 9H-2-aminopurine [S. Lobsiger, R. K. Sinha, M. Trachsel, and S. Leutwyler, J. Chem. Phys. 134, 114307 (2011)]. From the Lorentzian
Theoretical spectroscopy study of the low-lying electronic states of UX and UX+, X = F and Cl
Bross, David H.; Peterson, Kirk A.
2015-11-13
Spectroscopic constants (Te, re, B0, ωe, ωexe) have been calculated for the low-lying electronic states of UF, UF+, UCl, and UCl+ using complete active space 2nd-order perturbation theory (CASPT2), with a series of correlation consistent basis sets. The latter included those based on both pseudopotential (PP) and all-electron Douglas-Kroll-Hess (DK) Hamiltonians for the U atom. Spin orbit effects were included a posteri using the state interacting method using both PP and Breit Pauli (BP) operators, as well as from exact two-component (X2C) methods for U+ and UF+. Complete basis set (CBS) limits were obtained by extrapolation where possible and themore » PP and BP calculations were compared at their respective CBS limits. The PP-based method was shown to be reliable in calculating spectroscopic constants, in particular when using the state interacting method with CASPT2 energies (SO-CASPT2). The two component calculations were limited by computational resources and could not include electron correlation from the nominally closed shell 6s and 6p orbitals of U. UF and UCl were both calculated to have Ω=9/2 ground states. The first excited state of UCl was calculated to be an Ω=7/2 state at 78 cm-1 as opposed to the same state at 435 cm-1 in UF, and the other low-lying states of UCl showed a similar compression relative to UF. Likewise UF+ and UCl+ both have Ω=4 ground states and the manifold of low-lying excited Ω = 3, 2, 1, 0 states were energetically closer together in UCl+ than in UF+, ranging up to 776 cm-1 in UF+ and only 438 cm-1 in UCl+. As in previous research, the final PP-based SO-CASPT2 results for UF+ and UF agree well with experiment, and are expected to be predictive for UCl and UCl+, which are reported here for the first time.« less
Theoretical spectroscopy study of the low-lying electronic states of UX and UX{sup +}, X = F and Cl
Bross, David H.; Peterson, Kirk A.
2015-11-14
Spectroscopic constants (T{sub e}, r{sub e}, B{sub 0}, ω{sub e}, and ω{sub e}x{sub e}) have been calculated for the low-lying electronic states of UF, UF{sup +}, UCl, and UCl{sup +} using complete active space 2nd-order perturbation theory (CASPT2), with a series of correlation consistent basis sets. The latter included those based on both pseudopotential (PP) and all-electron Douglas-Kroll-Hess Hamiltonians for the U atom. Spin orbit (SO) effects were included a posteriori using the state interacting method using both PP and Breit Pauli (BP) operators, as well as from exact two-component methods for U{sup +} and UF{sup +}. Complete basis set (CBS) limits were obtained by extrapolation where possible and the PP and BP calculations were compared at their respective CBS limits. The PP-based method was shown to be reliable in calculating spectroscopic constants, in particular when using the state interacting method with CASPT2 energies (SO-CASPT2). The two component calculations were limited by computational resources and could not include electron correlation from the nominally closed shell 6s and 6p orbitals of U. UF and UCl were both calculated to have Ω = 9/2 ground states. The first excited state of UCl was calculated to be an Ω = 7/2 state at 78 cm{sup −1} as opposed to the same state at 435 cm{sup −1} in UF, and the other low-lying states of UCl showed a similar compression relative to UF. Likewise, UF{sup +} and UCl{sup +} both have Ω = 4 ground states and the manifold of low-lying excited Ω = 3, 2, 1, 0 states was energetically closer together in UCl{sup +} than in UF{sup +}, ranging up to 776 cm{sup −1} in UF{sup +} and only 438 cm{sup −1} in UCl{sup +}. As in previous studies, the final PP-based SO-CASPT2 results for UF{sup +} and UF agree well with experiment and are expected to be predictive for UCl and UCl{sup +}, which are reported here for the first time.
Marchal, Rémi; Carbonnière, Philippe; Pouchan, Claude
2015-01-22
The study of atomic clusters has become an increasingly active area of research in the recent years because of the fundamental interest in studying a completely new area that can bridge the gap between atomic and solid state physics. Due to their specific properties, such compounds are of great interest in the field of nanotechnology [1,2]. Here, we would present our GSAM algorithm based on a DFT exploration of the PES to find the low lying isomers of such compounds. This algorithm includes the generation of an intial set of structure from which the most relevant are selected. Moreover, an optimization process, called raking optimization, able to discard step by step all the non physically reasonnable configurations have been implemented to reduce the computational cost of this algorithm. Structural properties of Ga{sub n}Asm clusters will be presented as an illustration of the method.
Electronic structure and rovibrational calculation of the low-lying states of the RbYb molecule
NASA Astrophysics Data System (ADS)
Tohme, S. N.; Korek, M.
2013-01-01
Complete Active Space Self Consistent Field (CASSCF) method with Multi Reference Configuration Interaction (MRCI) calculations is used to investigate the potential energy curves of the low-lying 29 electronic states in the representation 2s+1Λ(+/-) of the RbYb molecule (single and double excitations with Davidson corrections). The harmonic frequency ωe, the internuclear distance Re and the electronic energy with respect to the ground state Te have been calculated. The eigenvalues Ev, the rotational constant Bv, and the abscissas of the turning points Rmin and Rmax have been investigated using the canonical functions approach. The comparison between the values of the present work and those available in the literature for several states shows a very good agreement. Twenty-six new states have been studied here for the first time.
Spin Tests of a Low-lying Monoplane in Flight and in the Free-spinning Wind Tunnel
NASA Technical Reports Server (NTRS)
Seidman, Oscar; Mcavoy, William H
1940-01-01
Comparative full-scale and model spin tests were made with a low-lying monoplane in order to extend the available information as to the utility of the free-spinning wind tunnel as an aid in predicting full-scale spin characteristics. For a given control disposition the model indicated steeper spins than were actually obtained with the airplane, the difference being most pronounced for spins with elevators up. Recovery characteristics for the model, on the whole, agreed with those for the airplane, but a disagreement was noted for the case of recovery with elevators held full up. Free-spinning wind-tunnel tests are a useful aid in estimating spin characteristics of airplanes, but it must be appreciated that model results can give only general indications of full-scale behavior.
Reduced transition strengths of low-lying yrast states in chromium isotopes in the vicinity of N =40
NASA Astrophysics Data System (ADS)
Braunroth, Thomas; Dewald, A.; Iwasaki, H.; Lenzi, S. M.; Albers, M.; Bader, V. M.; Baugher, T.; Baumann, T.; Bazin, D.; Berryman, J. S.; Fransen, C.; Gade, A.; Ginter, T.; Gottardo, A.; Hackstein, M.; Jolie, J.; Lemasson, A.; Litzinger, J.; Lunardi, S.; Marchi, T.; Modamio, V.; Morse, C.; Napoli, D. R.; Nichols, A.; Recchia, F.; Stroberg, S. R.; Wadsworth, R.; Weisshaar, D.; Whitmore, K.; Wimmer, K.
2015-09-01
Background: In neutron-rich nuclei around N =40 rapid changes in nuclear structure can be observed. While 68Ni exhibits signatures of a doubly magic nucleus, experimental data along the isotopic chains in even more exotic Fe and Cr isotopes—such as excitation energies and transition strengths—suggest a sudden rise in collectivity toward N =40 . Purpose: Reduced quadrupole transition strengths for low-lying transitions in neutron-rich 58,60,62Cr are investigated. This gives quantitative new insights into the evolution of quadrupole collectivity in the neutron-rich region close to N =40 . Method: The recoil distance Doppler-shift (RDDS) technique was applied to measure lifetimes of low-lying states in 58,60,62>Cr. The experiment was carried out at the National Superconducting Cyclotron Laboratory (NSCL) with the SeGA array in a plunger configuration coupled to the S800 magnetic spectrograph. The states of interest were populated by means of one-proton knockout reactions. Results: Data reveal a rapid increase in quadrupole collectivity for 58,60,62>Cr toward N =40 and point to stronger quadrupole deformations compared to neighboring Fe isotopes. The experimental B (E 2 ) values are reproduced well with state-of-the-art shell-model calculations using the LNPS effective interaction. A consideration of intrinsic quadrupole moments and B42 ratios suggest an evolution toward a rotational nature of the collective structures in Cr,6260. Compared to 58Cr, experimental B42 and B62 values for 60Cr are in better agreement with the E (5 ) limit. Conclusion: Our results indicate that collective excitations in neutron-rich Cr isotopes saturate at N =38 , which is in agreement with theoretical predictions. More detailed experimental data of excited structures and interband transitions are needed for a comprehensive understanding of quadrupole collectivity close to N =40 . This calls for additional measurements in neutron-rich Cr and neighboring Ti and Fe nuclei.
NASA Astrophysics Data System (ADS)
Holding, S.; Allen, D. M.
2015-02-01
Freshwater lenses on small islands are vulnerable to many climate change-related stressors, which can act over relatively long time periods, on the order of decades (e.g., sea level rise, changes in recharge), or short time periods, such as days (storm surge overwash). This study evaluates the response of the freshwater lens on a small low-lying island to various stressors. To account for the varying temporal and spatial scales of the stressors, two different density-dependent flow and solute transport codes are used: SEAWAT (saturated) and HydroGeoSphere (unsaturated/saturated). The study site is Andros Island in the Bahamas, which is characteristic of other low-lying carbonate islands in the Caribbean and Pacific regions. In addition to projected sea level rise and reduced recharge under future climate change, Andros Island experienced a storm surge overwash event during Hurricane Francis in 2004, which contaminated the main wellfield. Simulations of reduced recharge result in a greater loss of freshwater lens volume (up to 19%), while sea level rise contributes a lower volume loss (up to 5%) due to the flux-controlled conceptualization of Andros Island, which limits the impact of sea level rise. Reduced recharge and sea level rise were simulated as incremental instantaneous shifts. The lens responds relatively quickly to these stressors, within 0.5 to 3 years, with response time increasing as the magnitude of the stressor increases. Simulations of the storm surge overwash indicate that the freshwater lens recovers over time; however, prompt remedial action can restore the lens to potable concentrations up to 1 month sooner.
NASA Astrophysics Data System (ADS)
McPherson, David M.
An inverse kinematic proton scattering experiment was performed at the National Superconducting Cyclotron Laboratory (NSCL) using the GRETINA-S800 detector system in conjunction with the Ursinus College liquid hydrogen target. gamma-ray yields from the experiment were determined using geant4 simulations, generating state population cross sections. These cross sections were used to extract the delta_3 deformation length for the low-lying octupole vibration excitations in Ca-48,49 using the coupled channels analysis code fresco. Particle-core coupling in Ca-49 was studied in comparison to Ca-48 through determination of the neutron and proton deformation lengths. The total inverse kinematic proton scattering deformation lengths were evaluated for the low-lying octupole vibration excitations in Ca-48,49 to be delta_3(Ca-48, 3. -_1) = 1.0(2)fm,delta_3(Ca-49, 9/2. +_1) = 1.2(1)fm, delta_3 (Ca-49, 9/2. +_1) = 1.5(2)fm, delta_3(Ca-49,5/2. +_1) = 1.1(1)fm. Proton and neutron deformation lengths for two of theseoctupole states were also determined to be delta_p(Ca-48, 3. -_1) = 0.9(1)fm,delta_p (Ca-49, 9/2. +_1) = 1.0(1)fm, delta_n(Ca-48, 3. -_1) = 1.1(3)fm, anddelta_n(Ca-49, 9/2. +_1) = 1.3(3)fm. Additionally, the ratios of the neutronto proton transition matrix elements were also determined for these two states to be M_n/M_p(Ca-48, 3. -_1) = 1.7(6) and M_n/M_p(Ca-49, 9/2. +_1) = 2.0(5).Statistically, the derived values for these two nuclei are nearly identical.
NASA Astrophysics Data System (ADS)
Müller, Holger S. P.; Ordu, Matthias H.; Lewen, Frank; Brown, Linda; Drouin, Brian; Pearson, John; Sung, Keeyoon; Kleiner, Isabelle; Sams, Robert
2015-06-01
Rotational and rovibrational spectra of methyl cyanide were recorded to analyze interactions in low-lying vibrational states and to construct line lists for radio astronomical observations as well as for infrared spectroscopic investigations of planetary atmospheres. The rotational spectra cover large portions of the 36-1627~GHz region. In the infrared (IR), a spectrum was recorded for this study in the region of 2ν_8 around 717~cm-1 with assignments covering 684-765~cm-1. Additional spectra in the ν _8 region were used to validate the analysis. Using ν _8 data as well as spectroscopic parameters for v_4 = 1, v_7 = 1, and v_8 = 3 from previous studies, we analyzed rotational data involving v = 0, v_8 = 1, and v_8 = 2 up to high J and K quantum numbers. We analyzed a strong Δ v_8 = ± 1, Δ K = 0, Δ l = ±3 Fermi resonance between v_8 = 1-1 and v_8 = 2+2 at K = 14 and obtained preliminary results for two further Fermi resonances between v_8 = 2 and 3. We also found resonant Δ v_8 = ± 1, Δ K = ∓ 2, Δ l = ± 1 interactions between v_8 = 1 and 2 and present the first detailed analysis of such a resonance between v_8 = 0 and 1. We discuss the impact of this analysis on the v_8 = 1 and 2 as well as on the axial v = 0 parameters and compare selected CH_3CN parameters with those of CH_3CCH and CH_3NC. We evaluated transition dipole moments of ν _8, 2ν _8 - ν _8, and 2ν _8 for remote sensing in the IR. Part of this work was carried out at the Jet Propulsion Laboratory under contract with the National Aeronautics and Space Administration. M. Koivusaari et al., J. Mol. Spectrosc. 152 (1992) 377-388. A.-M. Tolonen et al., J. Mol. Spectrosc. 160 (1993) 554-565.
NASA Astrophysics Data System (ADS)
Minakawa, H.; Masumoto, T.
2012-12-01
An increase in flood risk, especially in low-lying areas, is predicted as a consequence of global climate change or other causes. Immediate measures such as strengthening of drainage capacity are needed to minimize the damage caused by more-frequent flooding. Typically, drainage pump capacities of in paddy areas are planned by using a result of drainage analysis with design rainfall (e.g. 3-day rainfall amount with a 10-year return period). However, the result depends on a hyetograph of input rainfall even if a total amount of rainfall is equal, and the flood risk may be different with rainfall patterns. Therefore, it is important to assume various patterns of heavy rainfall for flood risk assessment. On the other hand, a rainfall synthesis simulation is useful to generate many patterns of rainfall data for flood studies. We previously proposed a rainfall simulation method called diurnal rainfall pattern generator which can generate short-time step rainfall and internal pattern of them. This study discusses a quantitative evaluation method for detecting a relationship between flood damage risk and heavy rainfall scale by using the diurnal rainfall pattern generator. In addition, we also approached an estimation of flood damage which focused on rice yield. Our study area was in the Kaga three-lagoon basin in Ishikawa Prefecture, Japan. There are two lagoons in the study area, and the low-lying paddy areas extend over about 4,000 ha in the lower reaches of the basin. First, we developed a drainage analysis model that incorporates kinematic and diffusive runoff models for calculating water level on channels and paddies. Next, the heavy rainfall data for drainage analysis were generated. Here, the 3-day rainfalls amounts with 9 kinds of different return periods (2-, 3-, 5-, 8-, 10-, 15-, 50-, 100-, and 200-year) were derived, and three hundred hyetograph patterns were generated for each rainfall amount by using the diurnal rainfall pattern generator. Finally, all data
NASA Astrophysics Data System (ADS)
Kang, Jing; Cheng, Xiao
2014-05-01
Global sea level rise has certainly accelerated through the 21st and far beyond the previous projections and will continue to rise, while the frequencies and strength of extreme events such like flood and storm will increase due to global warming. Coastal cities where always be with densely population and accumulated social wealth will be under enormous affects. Using Landsat TM/ETM+ satellite images (1990, 2010) to extract urban built-up area, 17 China's developed coastal cities, which account for only 1.2% of total land area but boast 18.3% of urban population and nearly 19.6% of GDP in 2010, are spotted a 550% increase of urban land from 1990 to 2010. Shuttle Radar Topography Mission (SRTM) with 90m resolution data were used to calculate average elevation of extracted urban area. Then we found that these cities are all expanding seaward, occupying the most vulnerable neighborhoods, often in low-lying areas, alongside waterways prone to flooding. 11 cities show a reducing trend of mean elevations with the total average of more than 3 meters. Particularly, Shanghai, Tianjin and Ningbo in Delta area are most serious with the mean urban elevation less than 5 meters in 2010. The rapid expansion to seawards and accumulation of population and social wealth processed in coastal cities will increase the vulnerability and exposure, which will exacerbated the existing risks of rising sea level or extreme events. Referring to Defense Meteorological Satellite Program (DMSP/OLS) city-lights data and SRTM data, we built the Urban Vulnerability Index (UVI) to do semi-quantitative assessment on vulnerabilities of coastal cities. The UVI case study in GuangZhou showed the most vulnerability region concentrated at the low-lying south area where is with the much higher relative South Sea level than other sea area of China. With relative sea level rise of 1-1.5 m by 2100 and increased frequency of extreme sea level due to cyclone propagation, and weak urban drain-off system, Chinese
Nucleosynthesis of 92Nb and the relevance of the low-lying isomer at 135.5 keV
NASA Astrophysics Data System (ADS)
Mohr, Peter
2016-06-01
Background: Because of its half-life of about 35 million years, 92Nb is considered as a chronometer for nucleosynthesis events prior to the birth of our sun. The abundance of 92Nb in the early solar system can be derived from meteoritic data. It has to be compared to theoretical estimates for the production of 92Nb to determine the time between the last nucleosynthesis event before the formation of the early solar system. Purpose: The influence of a low-lying short-lived isomer on the nucleosynthesis of 92Nb is analyzed. The thermal coupling between the ground state and the isomer via so-called intermediate states affects the production and survival of 92Nb. Method: The properties of the lowest intermediate state in 92Nb are known from experiment. From the lifetime of the intermediate state and from its decay branchings, the transition rate from the ground state to the isomer and the effective half-life of 92Nb are calculated as functions of the temperature. Results: The coupling between the ground state and the isomer is strong. This leads to thermalization of ground state and isomer in the nucleosynthesis of 92Nb in any explosive production scenario and almost 100% survival of 92Nb in its ground state. However, the strong coupling leads to a temperature-dependent effective half-life of 92Nb which makes the 92Nb survival very sensitive to temperatures as low as about 8 keV, thus turning 92Nb at least partly into a thermometer. Conclusions: The low-lying isomer in 92Nb does not affect the production of 92Nb in explosive scenarios. In retrospect this validates all previous studies where the isomer was not taken into account. However, the dramatic reduction of the effective half-life at temperatures below 10 keV may affect the survival of 92Nb after its synthesis in supernovae, which are the most likely astrophysical sites for the nucleosynthesis of 92Nb.
Mirmiran, Roya; Squire, Chad; Wassell, Daniel
2015-01-01
A peroneus brevis low-lying muscle belly (LLMB) is a rare anomaly. A few published studies have supported the presence of this anomaly as an etiology for a peroneal tendon tear. However, the association between a peroneus brevis LLMB and tendon subluxation has not been well explored. In the present retrospective study, the magnetic resonance imaging (MRI) and intraoperative findings of 50 consecutive patients undergoing primary peroneal tendon surgery during a 5-year period were assessed. The sensitivity and specificity of MRI compared with the intraoperative findings for identifying peroneal tendon disease were investigated. The presence of associated peroneal tendon pathologic features in patients with and without a peroneus brevis LLMB was also compared. The sensitivity of MRI was high for identifying peroneal tenosynovitis (81.58%) and tear (85.71%). Although the sensitivity of MRI for detecting a peroneus brevis LLMB (3.23%) and tendon subluxation (10.00%) was low, MRI had high specificity at 94.74% and 100%, respectively. Intraoperatively, a peroneus brevis LLMB was seen in 62.00% of the patients with chronic lateral ankle pain and was associated with 64.52% of the patients with tenosynovitis, 29.03% of those with tendon subluxation, and 80.65% of those with a peroneus brevis tendon tear. Although the presence of a peroneus brevis LLMB did not show any statistically significant association with peroneus brevis tendon subluxation, of the 10 patients with intraoperatively observed tendon subluxation, 9 had a concomitant peroneus brevis LLMB. More studies with larger patient populations are needed to better investigate the role of a peroneus brevis LLMB as a mass-occupying lesion resulting in peroneal tendon subluxation. PMID:25998478
NASA Astrophysics Data System (ADS)
Hirano, Tsuneo; Okuda, Rei; Nagashima, Umpei; Jensen, Per
2012-12-01
FeCO is a molecule of astrophysical interest. We report here theoretical calculations of its geometrical parameters, electronic structures, and molecular constants (such as dipole moment and spin-orbit coupling constant) in the electronic ground state tilde{X}3Σ - and the low-lying triplet and quintet excited states. The calculations were made at the MR-SDCI+Q_DK3/[5ZP ANO-RCC (Fe, C, O)] and MR-AQCC_DK3/[5ZP ANO-RCC (Fe, C, O)] levels of theory. A multi-reference calculation was required to describe correctly the wavefunctions of all states studied. For all triplet states, the σ-donation through the 10σ molecular orbital (MO) as well as the π-back-donation through the 4π MO are observed, and the dipole moment vector points from O toward Fe as expected. However, in the excited quintet states 5Π, 5Φ, and 5Δ, the almost negligible contribution of Fe 4s to the 10σ MO makes the dipole moment vector point from Fe toward O, i.e., in the same direction as in CO. In the tilde{X}3Σ - state, the electron provided by the σ-donation through the 10σ MO is shared between the Fe atom and the C end of the CO residue to form a coordinate-covalent Fe-C bond. In the tilde{a}5Σ - state (the high-spin counterpart of tilde{X}3Σ -), the σ-donation through the 10σ MO is not significant and so the Fe-C bond is rather ionic. The π-back-donation through the 4π MO is found to be of comparable importance in the two electronic states; it has a slightly larger magnitude in the tilde{X}3Σ - state. The difference in the molecular properties of the low-spin tilde{X}3Σ - and the high-spin tilde{a}5Σ - states can be understood in terms of the dynamical electron correlation effects.
Da Lio, Cristina; Carol, Eleonora; Kruse, Eduardo; Teatini, Pietro; Tosi, Luigi
2015-11-15
The original morphology and hydrogeology of many low-lying coastlands worldwide have been significantly modified over the last century through river diversion, embankment built-up, and large-scale land reclamation projects. This led to a progressive shifting of the groundwater-surficial water exchanges from naturally to anthropogenically driven. In this human-influenced hydrologic landscape, the saltwater contamination usually jeopardizes the soil productivity. In the coastland south of Venice (Italy), several well log measurements, chemical and isotope analyses have been performed over the last decade to characterize the occurrence of the salt contamination. The processing of this huge dataset highlights a permanent variously-shaped saline contamination up to 20km inland, with different conditions in relation with the various geomorphological features of the area. The results point out the important role of the land reclamation in shaping the present-day salt contamination and reveal the contribution of precipitation, river discharge, lagoon and sea water to the shallow groundwater in the various coastal sectors. Moreover, an original vulnerability map to salt contamination in relation to the farmland productivity has been developed taking into account the electrical conductivity of the upper aquifer in the worst condition, the ground elevation, and the distance from salt and fresh surface water sources. Finally, the study allows highlighting the limit of traditional investigations in monitoring saltwater contamination at the regional scale in managed Holocene coastal environments. Possible improvements are outlined. PMID:26172603
Patacchiola, F; D'Alfonso, A; Di Fonso, A; Di Febbo, G; Kaliakoudas, D; Carta, G
2012-01-01
The aim of the present study was to evaluate the effectiveness of Bakri balloon in preventing and treating postpartum haemorrhage (PPH). Intrauterine Bakri balloon was used in a total of 16 patients with two different purposes: prophylactic placement of the balloon after cesarean section (CS) in six patients with low-lying placenta and therapeutic placement in ten patients with persistent bleeding from uterine atony, after spontaneous delivery, and administration of uterotonics. Intrauterine Bakri balloon was a successful approach in controlling and preventing PPH in all 16 patients. The median nadir hematocrit was 26.6% in six patients who underwent CS and 25.6% in ten patients with persistent bleeding after spontaneous delivery. The intrauterine balloon was in place for a duration of 24 hours. The median balloon infusion volume was 345 ml (range 250-455). No complications were reported. Bakri balloon tamponade was a useful measure in treating PPH unresponsive to pharmacological therapy in patients who delivered vaginally. Moreover, it was able to prevent persistent bleeding in patients who underwent CS for central placenta previa. PMID:23444752
Tohme, Samir N.; Korek, Mahmoud E-mail: fkorek@yahoo.com; Awad, Ramadan
2015-03-21
Ab initio techniques have been applied to investigate the electronic structure of the LiYb molecule. The potential energy curves have been computed in the Born–Oppenheimer approximation for the ground and 29 low-lying doublet and quartet excited electronic states. Complete active space self-consistent field, multi-reference configuration interaction, and Rayleigh Schrödinger perturbation theory to second order calculations have been utilized to investigate these states. The spectroscopic constants, ω{sub e}, R{sub e}, B{sub e}, …, and the static dipole moment, μ, have been investigated by using the two different techniques of calculation with five different types of basis. The eigenvalues, E{sub v}, the rotational constant, B{sub v}, the centrifugal distortion constant, D{sub v}, and the abscissas of the turning points, R{sub min} and R{sub max}, have been calculated by using the canonical functions approach. The comparison between the values of the present work, calculated by different techniques, and those available in the literature for several electronic states shows a very good agreement. Twenty-one new electronic states have been studied here for the first time.
Lee, Jae-Kwang; Fujiwara, Takashige; Kofron, William G.; Zgierski, Marek Z.; Lim, Edward C.
2008-04-28
Electronic absorption spectra of the low-lying {pi}{pi}* and {pi}{sigma}* states of several aminobenzonitriles and 4-dimethylaminobenzethyne have been studied by time-resolved transient absorption and time-dependent density functional theory calculation. In acetonitrile, the lifetime of the {pi}{sigma}*-state absorption is very short (picoseconds or subpicosecond) for molecules that exhibit intramolecular charge transfer (ICT), and very long (nanoseconds) for those that do not. Where direct comparison of the temporal characteristics of the {pi}{sigma}*-state and the ICT-state transients could be made, the formation rate of the ICT state is identical to the decay rate of the {pi}{sigma}* state within the experimental uncertainty. These results are consistent with the {pi}{sigma}*-mediated ICT mechanism, L{sub a} ({pi}{pi}*){yields}{pi}{sigma}*{yields}ICT, in which the decay rate of the {pi}{sigma}* state is determined by the rate of the solvent-controlled {pi}{sigma}*{yields}ICT charge-shift reaction. The {pi}{pi}*{yields}{pi}{sigma}* state crossing does not occur in 3-dimethylaminobenzonitrile or 2-dimethylaminobenzonitrile, as predicted by the calculation, and 4-aminobenzonitrile and 4-dimethylaminobenzethyne does not exhibit the ICT reaction, consistent with the higher energy of the ICT state relative to the {pi}{sigma}* state.
Li, Shaohong L; Xu, Xuefei; Truhlar, Donald G
2015-08-21
Three singlet states, namely a closed-shell ground state and two excited states with (1)ππ* and (1)nσ* character, have been suggested to be responsible for the radiationless decay or photochemical reaction of photoexcited thioanisole. The correct interpretation of the electronic spectrum is critical for understanding the character of these low-lying excited states, but the experimental spectrum is yet to be fully interpreted. In the work reported here, we investigated the nature of those three states and a fourth singlet state of thioanisole using electronic structure calculations by multireference perturbation theory, by completely-renormalized equation-of-motion coupled cluster theory with single and double excitations and noniterative inclusion of connected triples (CR-EOM-CCSD(T)), and by linear-response time-dependent density functional theory (TDDFT). We clarified the assignment of the electronic spectrum by simulating it using a normal-mode sampling approach combined with TDDFT in the Tamm-Dancoff approximation (TDA). The understanding of the electronic states and of the accuracy of the electronic structure methods lays the foundation of our future work of constructing potential energy surfaces. PMID:26088195
Operational flood control of a low-lying delta system using large time step Model Predictive Control
NASA Astrophysics Data System (ADS)
Tian, Xin; van Overloop, Peter-Jules; Negenborn, Rudy R.; van de Giesen, Nick
2015-01-01
The safety of low-lying deltas is threatened not only by riverine flooding but by storm-induced coastal flooding as well. For the purpose of flood control, these deltas are mostly protected in a man-made environment, where dikes, dams and other adjustable infrastructures, such as gates, barriers and pumps are widely constructed. Instead of always reinforcing and heightening these structures, it is worth considering making the most of the existing infrastructure to reduce the damage and manage the delta in an operational and overall way. In this study, an advanced real-time control approach, Model Predictive Control, is proposed to operate these structures in the Dutch delta system (the Rhine-Meuse delta). The application covers non-linearity in the dynamic behavior of the water system and the structures. To deal with the non-linearity, a linearization scheme is applied which directly uses the gate height instead of the structure flow as the control variable. Given the fact that MPC needs to compute control actions in real-time, we address issues regarding computational time. A new large time step scheme is proposed in order to save computation time, in which different control variables can have different control time steps. Simulation experiments demonstrate that Model Predictive Control with the large time step setting is able to control a delta system better and much more efficiently than the conventional operational schemes.
Tohme, Samir N; Korek, Mahmoud; Awad, Ramadan
2015-03-21
Ab initio techniques have been applied to investigate the electronic structure of the LiYb molecule. The potential energy curves have been computed in the Born-Oppenheimer approximation for the ground and 29 low-lying doublet and quartet excited electronic states. Complete active space self-consistent field, multi-reference configuration interaction, and Rayleigh Schrödinger perturbation theory to second order calculations have been utilized to investigate these states. The spectroscopic constants, ωe, Re, Be, …, and the static dipole moment, μ, have been investigated by using the two different techniques of calculation with five different types of basis. The eigenvalues, Ev, the rotational constant, Bv, the centrifugal distortion constant, Dv, and the abscissas of the turning points, Rmin and Rmax, have been calculated by using the canonical functions approach. The comparison between the values of the present work, calculated by different techniques, and those available in the literature for several electronic states shows a very good agreement. Twenty-one new electronic states have been studied here for the first time. PMID:25796254
NASA Astrophysics Data System (ADS)
Tohme, Samir N.; Korek, Mahmoud; Awad, Ramadan
2015-03-01
Ab initio techniques have been applied to investigate the electronic structure of the LiYb molecule. The potential energy curves have been computed in the Born-Oppenheimer approximation for the ground and 29 low-lying doublet and quartet excited electronic states. Complete active space self-consistent field, multi-reference configuration interaction, and Rayleigh Schrödinger perturbation theory to second order calculations have been utilized to investigate these states. The spectroscopic constants, ωe, Re, Be, …, and the static dipole moment, μ, have been investigated by using the two different techniques of calculation with five different types of basis. The eigenvalues, Ev, the rotational constant, Bv, the centrifugal distortion constant, Dv, and the abscissas of the turning points, Rmin and Rmax, have been calculated by using the canonical functions approach. The comparison between the values of the present work, calculated by different techniques, and those available in the literature for several electronic states shows a very good agreement. Twenty-one new electronic states have been studied here for the first time.
Vector analyzing power of {pi}{sup +7}Li scattering in the region of the {delta}{sub 33} resonance
Ibraeva, E. T.; Zhusupov, M. A.; Zaykin, A. Yu.; Imambekov, O.
2006-04-15
Within Glauber diffraction theory, the vector analyzing power iT{sub 11} is calculated at three energies of positively charged pions, 134, 164, and 194 MeV, incident to {sup 7}Li nuclei. These energy values lie in the region of the {delta}{sub 33} resonance in {pi}{sup {+-}}N interaction, the resonance maximum being at 180 MeV. The calculation of iT{sub 11} was performed with several model {sup 7}Li wave functions, including the {alpha}t-cluster and shell-model ones. The properties of {pi}{sup +7}Li scattering are found to be sensitive to the structural features of the target nucleus. A comparison of the results of the calculations with experimental data shows that the wave functions in question and the potentials used to calculate them are quite appropriate.
Ab initio MRSDCI study on the low-lying electronic states of the lithium chloride molecule (LiCl)
NASA Astrophysics Data System (ADS)
Kurosaki, Yuzuru; Yokoyama, Keiichi
2012-08-01
Potential energy curves (PECs) for the low-lying states of the lithium chloride molecule (LiCl) have been calculated using the internally contracted multireference single- and double-excitation configuration interaction (MRSDCI) method with the aug-cc-PVnZ (AVnZ) and aug-cc-PCVnZ (ACVnZ) basis sets, where n = T, Q, and 5. First, we calculate PECs for 7 spin-orbit (SO)-free Λ-S states, X1Σ+, A1Σ+, 3Σ+, 1Π, and 3Π, and then obtain PECs for 13 SO Ω states, X0+, A0+, B0+, 0-(I), 0-(II), 1(I), 1(II), 1(III), and 2, by diagonalizing the matrix of the electronic Hamiltonian plus the Breit-Pauli SO Hamiltonian. The MRSDCI calculations not including core orbital correlation through the single and double excitations are also performed with the AV5Z and ACV5Z basis sets. The Davidson corrections (Q0) are added to both the Λ-S and Ω state energies. Vibrational eigenstates for the obtained X1Σ+ and X0+ PECs are calculated by solving the time-independent Schrödinger equation with the grid method. Thus, the effects of basis set, core orbital correlation, and the Davidson correction on the X1Σ+ and X0+ PECs of LiCl are investigated by comparing the spectroscopic constants calculated from the PECs with one another and with experiment. It is confirmed that to accurately predict the spectroscopic constants we need to include core-electron correlation in the CI expansion and use the basis sets designed to describe core-valence correlation, i.e., ACVnZ. The SO PECs presented in this paper will be of help in the future study of diatomic alkali halide dynamics.
NASA Astrophysics Data System (ADS)
Goswami, Ganesh Chandra
Differential cross sections have been measured for the ground state and for the low-lying levels of ('232)Th, ('235)U, ('238)U via neutron time-of-flight technique. This work consists of the study of neutron scattering cross sections in the following areas: (i) The cross sections of ('232)Th in the incident energy range 185-2400 keV for ground state rotational band (GSRB) levels 0('+) (ground state), 2('+) (49 keV), and 4('+) (162 keV), (ii) the cross sections of ('235)U at incident energies of 185 keV and 550 keV for groups of levels, ground state + 77 eV + 13 keV and 46 + 52 keV, and (iii) the cross sections of ('238)U in the incident energy range 185-920 keV for GSRB levels 0('+) (ground state), 2('+) (45 keV) and 4('+) (148 keV). The University of Lowell 5.5 MV pulsed Van -de-Graaff accelerator with Mobley bunching system was employed. Neutrons were generated via the ('7)Li(p,n)('7)Be reaction in a metallic lithium target having thickness 8-10 keV. An overall resolution of 15-20 keV was maintained throughout the measurements. The scatterers were disk shaped. Careful attention has been paid to data reduction, angular resolution, multiple scattering corrections, and attenuation corrections. The results are compared with data of other investigators and ENDF/B-V.
Study of low-lying electronic states of ozone by multireference Møller-Plesset perturbation method
NASA Astrophysics Data System (ADS)
Tsuneda, T.; Nakano, H.; Hirao, K.
1995-10-01
The geometry and relative energy of the seven low-lying electronic states of ozone and the ground state of ozonide anion have been determined in C2v symmetry by the complete active space self-consistent field (CASSCF) and the multireference Møller-Plesset perturbation (MRMP) methods. The results are compared with the photodetachment spectra of O-3 observed recently by Arnold et al. The theoretical electron affinity of ozone is 1.965 eV, which is 0.14 eV below the experimental result of 2.103 eV. The calculated adiabatic excitation energies (assignment of Arnold et al. in parentheses) of ozone are 3A2 0.90 eV (1.18 eV), 3B2, 1.19 eV (1.30 eV), 3B1, 1.18 eV (1.45 eV), 1A2, 1.15 eV (˜1.6 eV), 1B1, 1.65 eV (2.05 eV), and 1B2, 3.77 eV (3.41 eV), respectively. Overall the present theory supports the assignment of Arnold et al. However, the simple considerations of geometry and energy are insufficient to determine a specific assignment of the 3B2 and 3B1 states. The dissociation energy of the ground state of ozone is computed to be 0.834 eV at the present level of theory. The present theory also predicts that none of the excited states lies below the ground state dissociation limit of O3.
Ab initio MRSDCI study on the low-lying electronic states of the lithium chloride molecule (LiCl).
Kurosaki, Yuzuru; Yokoyama, Keiichi
2012-08-14
Potential energy curves (PECs) for the low-lying states of the lithium chloride molecule (LiCl) have been calculated using the internally contracted multireference single- and double-excitation configuration interaction (MRSDCI) method with the aug-cc-PVnZ (AVnZ) and aug-cc-PCVnZ (ACVnZ) basis sets, where n = T, Q, and 5. First, we calculate PECs for 7 spin-orbit (SO)-free Λ-S states, X(1)Σ(+), A(1)Σ(+), (3)Σ(+), (1)Π, and (3)Π, and then obtain PECs for 13 SO Ω states, X0(+), A0(+), B0(+), 0(-)(I), 0(-)(II), 1(I), 1(II), 1(III), and 2, by diagonalizing the matrix of the electronic Hamiltonian plus the Breit-Pauli SO Hamiltonian. The MRSDCI calculations not including core orbital correlation through the single and double excitations are also performed with the AV5Z and ACV5Z basis sets. The Davidson corrections (Q0) are added to both the Λ-S and Ω state energies. Vibrational eigenstates for the obtained X(1)Σ(+) and X0(+) PECs are calculated by solving the time-independent Schrödinger equation with the grid method. Thus, the effects of basis set, core orbital correlation, and the Davidson correction on the X(1)Σ(+) and X0(+) PECs of LiCl are investigated by comparing the spectroscopic constants calculated from the PECs with one another and with experiment. It is confirmed that to accurately predict the spectroscopic constants we need to include core-electron correlation in the CI expansion and use the basis sets designed to describe core-valence correlation, i.e., ACVnZ. The SO PECs presented in this paper will be of help in the future study of diatomic alkali halide dynamics. PMID:22897271
Excitation of the low lying vibrational levels of H2O by O(3P) as measured on Spacelab 2
NASA Technical Reports Server (NTRS)
Meyerott, R. E.; Swenson, G. R.; Schweitzer, E. L.; Koch, D. G.
1994-01-01
The data from the infrared telescope (IRT), which was flown on space shuttle Challenger Spacelab 2 mission (July 1985), were originally reported by Koch et al. (1987) as originating from near orbital emissions, primarily H2O. In this study, analysis of this data was extended to determine the collisional cross sections for the excitation of the low lying vibrational levels of H2O, present in the orbiter cloud, by atmospheric O(3P). The evaluation of the contribution to the measured signal from solar excitation and ram O excitation of outgassing H2O permits the determination of the H2O column density and the excitation cross section of the (101) level at an O(3P) velocity of approximately 7.75 km/s. Contributions to the radiation in the 1.7-3.0 micron band by transitions from the (100), (001), and multiquantum excited levels are discussed. The findings of the study are (1) the IRT data for the 4.5-9.5 micron and the nighttime data for the 1.7-3.0 micron sensors are consistent with being explained by collision excitation of H2O by O(3P), (2) diurnal variations of 4.5-9.5 micron intensities follow the model predicted O density for a full orbit, (3) daytime increases in the H2O cloud density were not evident, (4) the cross sections for the collisional excitation process are derived and compared to values computated by Johnson (1986) and Redmon et al. (1986), (5) theoretical investigation suggests greater than 60% of the radiation from H2O is a result of multiphoton emission resulting from collisional multiquanta excitation, and (6) the large daytime increase in the 1.7-3.0 micron intensity data suggests that O(+) may likely be instrumental in producing excited H2O(+) through charge exchange.
Excitation of the low lying vibrational levels of H2O by O(3P) as measured on Spacelab 2
NASA Astrophysics Data System (ADS)
Meyerott, R. E.; Swenson, G. R.; Schweitzer, E. L.; Koch, D. G.
1994-09-01
The data from the infrared telescope (IRT), which was flown on space shuttle Challenger Spacelab 2 mission (July 1985), were originally reported by Koch et al. (1987) as originating from near orbital emissions, primarily H2O. In this study, analysis of this data was extended to determine the collisional cross sections for the excitation of the low lying vibrational levels of H2O, present in the orbiter cloud, by atmospheric O(3P). The evaluation of the contribution to the measured signal from solar excitation and ram O excitation of outgassing H2O permits the determination of the H2O column density and the excitation cross section of the (101) level at an O(3P) velocity of approximately 7.75 km/s. Contributions to the radiation in the 1.7-3.0 micron band by transitions from the (100), (001), and multiquantum excited levels are discussed. The findings of the study are (1) the IRT data for the 4.5-9.5 micron and the nighttime data for the 1.7-3.0 micron sensors are consistent with being explained by collision excitation of H2O by O(3P), (2) diurnal variations of 4.5-9.5 micron intensities follow the model predicted O density for a full orbit, (3) daytime increases in the H2O cloud density were not evident, (4) the cross sections for the collisional excitation process are derived and compared to values computated by Johnson (1986) and Redmon et al. (1986), (5) theoretical investigation suggests greater than 60% of the radiation from H2O is a result of multiphoton emission resulting from collisional multiquanta excitation, and (6) the large daytime increase in the 1.7-3.0 micron intensity data suggests that O(+) may likely be instrumental in producing excited H2O(+) through charge exchange.
Karmakar, Shreetama; Mukhopadhyay, Deb Pratim; Chakraborty, Tapas
2015-05-14
Multiple fluorine atom substitution effect on photophysics of an aromatic chromophore has been investigated using phenol as the reference system. It has been noticed that the discrete vibronic structure of the S{sub 1}←S{sub 0} absorption system of phenol vapor is completely washed out for pentafluorophenol (PFP), and the latter also shows very large Stokes shift in the fluorescence spectrum. For excitations beyond S{sub 1} origin, the emission yield of PFP is reduced sharply with increase in excess vibronic energy. However, in a collisional environment like liquid hydrocarbon, the underlying dynamical process that drives the non-radiative decay is hindered drastically. Electronic structure theory predicts a number of low-lying dark electronic states of πσ{sup ∗} character in the vicinity of the lowest valence ππ{sup ∗} state of this molecule. Tentatively, we have attributed the excitation energy dependent non-radiative decay of the molecule observed only in the gas phase to an interplay between the lowest ππ{sup ∗} and a nearby dissociative πσ{sup ∗} state. Measurements in different liquids reveal that some of the dark excited states light up with appreciable intensity only in protic liquids like methanol and water due to hydrogen bonding between solute and solvents. Electronic structure theory methods indeed predict that for PFP-(H{sub 2}O){sub n} clusters (n = 1-11), intensities of a number of πσ{sup ∗} states are enhanced with increase in cluster size. In contrast with emitting behavior of the molecule in the gas phase and solutions of nonpolar and polar aprotic liquids, the fluorescence is completely switched off in polar protic liquids. This behavior is a chemically significant manifestation of perfluoro effect, because a very opposite effect occurs in the case of unsubstituted phenol for which fluorescence yield undergoes a very large enhancement in protic liquids. Several dynamical mechanisms have been suggested to interpret the
Coastline evolution of Portuguese low-lying sandy coast in the last 50 years: an integrated approach
NASA Astrophysics Data System (ADS)
Ponte Lira, Cristina; Nobre Silva, Ana; Taborda, Rui; Freire de Andrade, Cesar
2016-06-01
Regional/national-scale information on coastline rates of change and trends is extremely valuable, but these studies are scarce. A widely accepted standardized methodology for analysing long-term coastline change has been difficult to achieve, but it is essential to conduct an integrated and holistic approach to coastline evolution and hence support coastal management actions. Additionally, databases providing knowledge on coastline evolution are of key importance to support both coastal management experts and users.The main objective of this work is to present the first systematic, national-scale and consistent long-term coastline evolution data of Portuguese mainland low-lying sandy coasts.The methodology used quantifies coastline evolution using a unique and robust coastline indicator (the foredune toe), which is independent of short-term changes.The dataset presented comprises (1) two polyline sets, mapping the 1958 and 2010 sandy beach-dune system coastline, both optimized for working at 1 : 50 000 scale or smaller; (2) one polyline set representing long-term change rates between 1958 and 2010, each estimated at 250 m; and (3) a table with minimum, maximum and mean of evolution rates for sandy beach-dune system coastline. All science data produced here are openly accessible at https://doi.pangaea.de/10.1594/PANGAEA.859136 and can be used in other studies.Results show beach erosion as the dominant trend, with a mean change rate of -0.24 ± 0.01 m year-1 for all mainland Portuguese beach-dune systems. Although erosion is dominant, this evolution is variable in signal and magnitude in different coastal sediment cells and also within each cell. The most relevant beach erosion issues were found in the coastal stretches of Espinho-Torreira and Costa Nova-Praia de Mira, Cova da Gala-Leirosa, and Cova do Vapor-Costa da Caparica. The coastal segments Minho River-Nazaré and Costa da Caparica
NASA Astrophysics Data System (ADS)
Samala, Nagaprasad Reddy; Mahapatra, S.
2014-06-01
Polycyclic aromatic hydrocarbons (PAHs), in particular, their radical cation (PAH^+), have long been postulated to be the important molecular species in connection with the spectroscopic observations in the interstellar medium. Motivated by numerous important observations by stellar as well as laboratory spectroscopists, we undertook detailed quantum mechanical studies of the structure and dynamics of electronically excited PAH^+ in an attempt to establish possible synergism with the recorded data In this study, we focus on the quantum chemistry and dynamics of the doublet ground (X) and low-lying excited (A, B and C) electronic states of the radical cation of tetracene (Tn), pentacene (Pn), and hexacene (Hn) molecule. This study is aimed to unravel photostability, spectroscopy, and time-dependent dynamics of their excited electronic states. In order to proceed with the theoretical investigations, we construct suitable multistate and multimode Hamiltonian for these systems with the aid of extensive ab initio calculations of their electronic energy surfaces. The diabatic coupling surfaces are derived from the calculated adiabatic electronic energies. First principles nuclear dynamics calculations are then carried out employing the constructed Hamiltonians and with the aid of time-independent and time-dependent quantum mechanical methods. We compared our theoretical results with available photoelectron spectroscopy, zero kinetic energy photoelectron (ZEKE) spectroscopy and matrix isolation spectroscopy (MIS) results. A peak at 8650 Å in the B state spectrum of Tn^+ is in good agreement with the DIB at 8648 Å observed by Salama et al. Similarly in Pn^+, a peak at 8350 Å can be correlated to the DIB at 8321 Å observed by Salama et al. J. Zhang et al., J. Chem. Phys., 128,104301 (2008).; F. Salama, Origins of Life Evol. Biosphere, 28, 349 (1998).; F. Salama et al., Planet. Space Sci., 43, 1165 (1995).; F. Salama et al., Astrophys. J., 526, 265 (1999).; J
Observation of Pseudoscalar and Axial Vector Resonances in pi- p -> K+ K- pi0 n at 18 GeV
G.S. Adams; T. Adams; Z. Bar-Yam; J.M. Bishop; V.A. Bodyagin; D.S. Brown; N.M. Cason; S.U. Chung; J.P. Cummings; K. Danyo; A.I. Demianov; S. Denisov; V. Dorofeev; J.P. Dowd; P. Eugenio; X.L. Fan; A.M. Gribushin; R.W. Hackenburg; M. Hayek; J. Hu; E.I. Ivanov; D. Joffe; I. Kachaev; W. Kern; E. King; O.L. Kodolova; V.L. Korotkikh; M.A. Kostin; Joachim Kuhn; V. Lipaev; J.M. Losecco; M. Lu; J.J. Manak; J. Napolitano; M. Nozar; C. Olchanski; A.I. Ostrovidov; T.K. Pedlar; A. Popov; D. Ryabchikov; A.H. Sanjari; L.I. Sarycheva; K.K. Seth; N. Shenhav; X. Shen; W.D. Shephard; N.B. Sinev; D.L. Stienike; S.A. Taegar; D.R. Thompson; A. Tomaradze; I.N. Vardanyan; D.P. Weygand; D. White; H.J. Willutzki; A.A. Yershov
2001-09-01
The number of pseudoscalar mesons in the mass range from 1400 to 1500 MeV/c{sup 2} has been a subject of considerable interest for many years, with several experiments having presented evidence for two closely spaced states. A new measurement of the reaction {pi}{sup -} p {yields} K{sup +} K{sup -} {pi}{sup 0}n has been made at a beam energy of 18 GeV. A partial wave analysis of the K{sup +} K{sup -} {pi}{sup 0} system shows evidence for three pseudoscalar resonances, {eta}(1295), {eta}(1416), and {eta}(1485), as well as two axial vectors, f{sub 1}(1285), and f{sub 1}(1420). Their observed masses, widths and decay properties are reported. No signal was observed for C(1480), an I{sub G} J{sup PC} = 1{sup +} 1{sup --} state previously reported in {phi}{pi}{sup 0} decay.
Sub-terahertz spectroscopy of magnetic resonance in BiFeO3 using a vector network analyzer
NASA Astrophysics Data System (ADS)
Caspers, Christian; Gandhi, Varun P.; Magrez, Arnaud; de Rijk, Emile; Ansermet, Jean-Philippe
2016-06-01
Detection of sub-THz spin cycloid resonances (SCRs) of stoichiometric BiFeO3 (BFO) was demonstrated using a vector network analyzer. Continuous wave absorption spectroscopy is possible, thanks to heterodyning and electronic sweep control using frequency extenders for frequencies from 480 to 760 GHz. High frequency resolution reveals SCR absorption peaks with a frequency precision in the ppm regime. Three distinct SCR features of BFO were observed and identified as Ψ1 and Φ2 modes, which are out-of-plane and in-plane modes of the spin cycloid, respectively. A spin reorientation transition at 200 K is evident in the frequency vs temperature study. The global minimum in linewidth for both Ψ modes at 140 K is ascribed to the critical slowing down of spin fluctuations.
Larsen, Curt; Clark, Inga; Guntenspergen, Glenn; Cahoon, Don; Caruso, Vincent; Hupp, Cliff; Yanosky, Tom
2004-01-01
shallow water surfaces has solved this problem. Our team has developed a detailed LIDAR map of the BNWR area at a 30 centimeter (ca. 1 ft) contour interval (figure 2). The new map allows us to identify the present marsh vegetation zones and to predict the location and area of future zones on a decade-by- decade basis over the next century at increments of sea level rise on the order of 3 cm/decade (ca. 1 inch). We have developed two scenarios for the model. The first is a steady-state model that uses the historic rate of sea level rise of 3.1 mm/yr to predict marsh areas. The second is a 'global warming' scenario utilizing a conservative IPCC model with an exponentially-increasing rate of sea level rise. Under either scenario, the BNWR is progressively inundated with an expanding core of open water. Although their positions change in the future, the areas of intertidal marsh as well as those of the critical high marsh remain fairly constant until the year 2050. Beyond that time, the low-lying land surface is overtopped by rising sea level and the area is dominated by open water. Our model suggests that wetland habitat in the Blackwater area might be maintained and sustained through a combination of public and private preservation efforts through easements in combination with judicious Federal land acquisition into the predicted areas of suitable marsh formation - but for only the next 50 years. Beyond that time much of this area will become open water.
NASA Astrophysics Data System (ADS)
Minakawa, H.; Masumoto, T.
2013-12-01
constructed in a rice paddy plot, which consisted of two zones, one in which the rice was cultivated as usual with normal water levels, and a flood zone, which was used for submerging rice plants. The flood zone, which was designed to reproduce actual flood disaster conditions in paddy fields, can be filled with water to a depth of 0.3, 0.6 or 0.9 m above ground level, and is divided into two plots, a clean water part and a turbid water part. Thus, the experimental conditions can vary according to 1) the development stage of rice, 2) complete or incomplete submersion, 3) clean or turbid water, and 4) duration of submergence. Finally, the reduction scales were formulated by using the resultant data and it was found that rice is most sensitive to damage during the development stage. Flood risk was evaluated by using calculated water level on each paddy. Here, the averaged duration of inundation to a depth of more than 0.3 m was used as the criteria for flood occurrence. The results indicated that the duration increased with larger heavy rainfall amounts. Furthermore, the damage to rice was predicted to increase especially in low-lying paddy fields. Mitigation measures, such as revising drainage planning and/or changing design standards for the capacity of drainage pumps may be necessary in the future.
NASA Astrophysics Data System (ADS)
Rangel, Tonatiuh; Sharifzadeh, Sahar; Rinn, Andre; da Jornada, Felipe H.; Shao, Meiyue; Witte, Gregor; Yang, Chao; Louie, Steven G.; Chatterjee, Sangaam; Kronik, Leeor; Neaton, Jeffrey B.
Organic semiconductors have attracted attention due to their potential for optoelectronics and novel phenomena, such as singlet fission. Here, we use many-body perturbation theory to simulate neutral excitations in acene and perylene crystals. By diagonalizing the full Bethe-Salpether (BSE) Hamiltonian beyond the Tamm Dancoff approximation (TDA), we find that both low-lying excitation energies and oscillator strengths are in improved agreement with experiments relative to the TDA. We characterize the low-lying excitons, focusing in the degree of charge-transfer and spatial delocalization, connecting their relevance to singlet fission. For perylene, we find overall good agreement with absorption measurements, and we see evidence for the formation of an ``exciton-polariton'' band in β-perylene. This work is supported by the DOE.
NASA Astrophysics Data System (ADS)
Berriche, Hamid; Gadea, Florent Xavier
1995-12-01
The permanent dipole moments of the eight low-lying 1Σ states of the LiH molecule are calculated by an ab initio approach for both the adiabatic and the diabatic representations. The results shed light on the interplay between the ionic and the neutral states producing a direct illustration of the ionic character of the electronic wavefunction. Our results suggest that the location and the width of the avoided crossings for the potential energy curves could be experimentally derived.
A potential-energy surface study of the 2A1 and low-lying dissociative states of the methoxy radical
NASA Technical Reports Server (NTRS)
Jackels, C. F.
1985-01-01
Accurate, ab initio quantum chemical techniques are applied in the present study of low lying bound and dissociative states of the methoxy radical at C3nu conformations, using a double zeta quality basis set that is augmented with polarization and diffuse functions. Excitation energy estimates are obtained for vertical excitation, vertical deexcitation, and system origin. The rate of methoxy photolysis is estimated to be too small to warrant its inclusion in atmospheric models.
Narra, Sudhakar; Shigeto, Shinsuke
2015-03-01
Low-lying excited triplet states of aromatic carbonyl compounds exhibit diverse photophysical and photochemical properties of fundamental importance. Despite tremendous effort in studying those triplet states, the effects of substituents and solvents on the energetics of the triplet manifold and on photoreactivity remain to be fully understood. We have recently studied the ordering of the low-lying nπ* and ππ* excited triplet states and its substituent dependence in acetophenone derivatives using nanosecond time-resolved near-IR (NIR) spectroscopy. Here we address the other important issue, the solvent effects, by directly observing the electronic bands in the NIR that originate from the lowest nπ* and ππ* states of acetophenone derivatives in four solvents of different polarity (n-heptane, benzene, acetonitrile, and methanol). The two transient NIR bands decay synchronously in all the solvents, indicating that the lowest nπ* and ππ* states are in thermal equilibrium irrespective of the solvent polarity studied here. We found that the ππ* band increases in intensity relative to the nπ* band as solvent polarity increases. These results are compared with the photoreduction rate constant for the acetophenone derivatives in the solvents to which 2-propanol was added as a hydrogen-atom donor. Based on the present findings, we present a comprehensive, solvent- and substituent-dependent energy level diagram of the low-lying nπ* and ππ* excited triplet states. PMID:25686256
Watari, H; Murakami, M; Seo, Y; Shimoyama, Y
1989-07-31
Superimposed plots of electron paramagnetic resonance spectra with the first and second harmonic displays of ferrihemoglobin at pH 9.1 and 90 K were measured at 20 degree intervals of phase angle using a phase-sensitive detector. The high spin signal in the g = 6 region was observed in both displays, and a small splitting of the signal was found in the calculated amplitude spectrum of the second harmonic display, with g values of 5.95 and 6.05. Low spin signals were observed at g = 2.55, 2.25 and 1.82 in both harmonic displays. A signal in the g = 2.05 region was observed only in the second harmonic display. The signal is probably associated with the low spin spectrum; however, its origin is obscure. PMID:2547369
NASA Astrophysics Data System (ADS)
Wang, Peng; Nakamura, Ryosuke; Kanematsu, Yasuo; Koyama, Yasushi; Nagae, Hiroyoshi; Nishio, Tomohiro; Hashimoto, Hideki; Zhang, Jian-Ping
2005-07-01
Electronic absorption spectra were recorded at room temperature in solutions of carotenoids having different numbers of conjugated double bonds, n = 8-13, including a spheroidene derivatives, neurosporene, spheroidene, lycopene, anhydrorhodovibrin and spirilloxanthin. The vibronic states of 1Bu+(v=0-4), 2Ag-(v=0-3), 3Ag- (0) and 1Bu- (0) were clearly identified. The arrangement of the four electronic states determined by electronic absorption spectroscopy was identical to that determined by measurement of resonance Raman excitation profiles [K. Furuichi et al., Chem. Phys. Lett. 356 (2002) 547] for carotenoids in crystals.
Guo, Jin-Chang; Hou, Gaolei; Li, Si-Dian; Wang, Xue B.
2012-02-02
Despite a seemingly simple appearance, cyclobutanetetraone (C{sub 4}O{sub 4}) has four low-lying electronic states. Determining the energetic ordering of these states and the ground state of C{sub 4}O{sub 4}{sup -} theoretically has been proven to be considerably challenging and remains largely unresolved to date. Here we report a low-temperature negative ion photoelectron spectroscopic approach. A well structured spectrum with evenly spaced features was obtained at 193 nm due to excitation of the ring breathing mode of the C{sub 4}O{sub 4} neutral, whereas each 193-nm feature was observed to further split into a three-peak manifold at 266 nm assigned due to three electronic transitions from the ground state of the anion to the ground and two low-lying excited states of the neutral. Combined with recent theoretical studies and our own Franck-Condon factors simulations, the ground state of C{sub 4}O{sub 4}{sup -}, as well as the ground and two low-lying excited states of C{sub 4}O{sub 4} are determined to be {sup 2}A{sub 2u}, and {sup 3}B{sub 2u}, {sup 1}A{sub 1g} (8{pi}), {sup 1}B{sub 2u}, respectively. The frequency of the ring breathing mode (1810 {+-} 20 cm{sup -1}), the electron affinity (3.475 {+-} 0.005 eV), and the term values of {sup 1}A{sub 1g} (8{pi}) (6.27 {+-} 0.5 kJ/mol) and {sup 1}B{sub 2u} (13.50 {+-} 0.5 kJ/mol) are also directly obtained from the experiments.
NASA Astrophysics Data System (ADS)
Tabar, Emre; Yakut, Hakan; Kuliev, Ali Akbar
2016-07-01
The ground state magnetic moments and the low-lying magnetic dipole (Ml) transitions from the ground to excited states in heavy deformed odd-mass 181Ta have been microscopically investigated on the basis of the quasiparticle-phonon nuclear model (QPNM). The problem of the spurious state mixing in M1 excitations is overcome by a restoration method allowing a self-consistent determination of the separable effective restoration forces. Due to the self-consistency of the method, these effective forces contain no arbitrary parameters. The results of calculations are compared with the available experimental data, the agreement being reasonably satisfactory.
Kowalski, Karol; Valiev, Marat
2007-01-01
High-level ab-initio equation-of-motion coupled-cluster methods with singles, doubles, and noniterative triples are used, in conjunction with the combined quantum mechanical molecular mechanics approach, to investigate the structure of low-lying excited states of the guanine base in DNA and solvated environments. Our results indicate that while the excitation energy of the first excited state is barely changed compared to its gas-phase counterpart, the excitation energy of the second excited state is blue-shifted by 0.24 eV.
Muller, H. S.; Brown, Linda R.; Drouin, B. J.; Pearson, J. C.; Kleiner, Isabelle; Sams, Robert L.; Sung, Keeyoon; Ordu, Matthias H.; Lewen, Frank
2015-06-01
Rotational and rovibrational spectra of methyl cyanide were recorded to analyze interactions in low-lying vibrational states and to construct line lists for radio astronomical observations as well as for infrared spectroscopic investigations of planetary atmospheres. The rotational spectra cover large portions of the 36-1627 GHz region. In the infrared (IR), a spectrum was recorded for this study in the region of 2v(8) around 717 cm(-1) with assignments covering 684-765 cm-1. Additional spectra in the vs region were used to validate the analysis.
Zou, Wenli; Suo, Bingbing
2016-08-18
The low-lying electronic states of platinum ions (Pt(+)) and platinum monohalides (PtX; X = F, Cl, Br, and I) are calculated using the multireference configuration interaction method with relativistic effective core potentials. The spin-orbit coupling is taken into account through the perturbative state-interaction approach. For the Ω states of PtX below 35000 cm(-1), the potential energy curves and the corresponding spectroscopic constants are reported. It is found that the lowest Ω = 3/2 state is the ground one for the four species of PtX. Overall, the theoretical results are in reasonable agreement with the available experimental data. PMID:27463417
NASA Astrophysics Data System (ADS)
Yao, J. M.; Engel, J.
2016-07-01
We present a generator-coordinate calculation, based on a relativistic energy-density functional, of the low-lying spectra in the isotopes 150Nd and 150Sm and of the nuclear matrix element that governs the neutrinoless double-β decay of the first isotope to the second. We carefully examine the impact of octupole correlations on both nuclear structure and the double-β decay matrix element. Octupole correlations turn out to reduce quadrupole collectivity in both nuclei. Shape fluctuations, however, dilute the effects of octupole deformation on the double-β decay matrix element, so that the overall octupole-induced quenching is only about 7 % .
NASA Technical Reports Server (NTRS)
Bauschlicher, C. W., Jr.; Silver, D. M.; Yarkony, D. R.
1980-01-01
The paper presents the multiconfiguration-self-consistent (MCSCF) and configuration state functions (CSF) for the low-lying electronic states of MgO. It was shown that simple description of these states was possible provided the 1 Sigma(+) states are individually optimized at the MCSCF level, noting that the 1(3 Sigma)(+) and 2(1 Sigma)(+) states which nominally result from the same electron occupation are separated energetically. The molecular orbitals obtained at this level of approximation should provide a useful starting point for extended configuration interaction calculations since they have been optimized for the particular states of interest.
NASA Astrophysics Data System (ADS)
Vershovskii, A. K.; Dmitriev, A. K.
2015-11-01
We used synchronous radio-frequency excitation of three components of a hyperfine resonance line in the scheme of the vector sensor of a magnetic field based on optically detected magnetic resonance in the nitrogen-vacancy centers in diamond crystal. As a result, for the first time, the sensitivity of order 1.5 nT Hz-1/2 in the frequency range of 0-100 Hz was reached in the crystal with a volume of 0.01 mm3 glued to the end of an optical fiber.
NASA Astrophysics Data System (ADS)
Pillet, N.; Zelevinsky, V. G.; Dupuis, M.; Berger, J.-F.; Daugas, J. M.
2012-04-01
A multiconfiguration microscopic method has been applied with the Gogny effective interaction to the calculation of low-lying positive-parity states in even-even 26-32Si isotopes. The aim of the study is to compare the results of this approach with those of a standard method of generator coordinate method (GCM) type and to get insight into the predictive power of multiconfiguration methods employed with effective nucleon-nucleon force tailored to mean-field calculations. It is found that the multiconfiguration approach leads to an excellent description of the low-lying spectroscopy of 26Si, 28Si, and 32Si, but gives a systematic energy shift in 30Si. A careful analysis of this phenomenon shows that this discrepancy originates from too large proton-neutron matrix elements supplied by the Gogny interaction at the level of the approximate resolution of the multiparticle-multihole configuration mixing method done in the present study. These proton-neutron matrix elements enter in the definition of both single-particle orbital energies and coupling matrix elements. Finally, a statistical analysis of highly excited configurations in 28Si is performed, revealing exponential convergence in agreement with previous work in the context of the shell model approach. This latter result provides strong arguments toward an implicit treatment of highly excited configurations.
Jun, Ye
2015-12-24
Low-lying band shapes of absorption and fluorescence spectra for a member of a newly synthesized family of phenylene-containing oligoacenes (POA 6) reported in J. Am. Chem. Soc. 2012 , 134 , 15351 are studied theoretically with two different approaches with TIPS-anthracene as a comparison. Underlying photophysics and exciton-phonon interactions in both molecules are investigated in details with the aid of the time-dependent density functional theory and multimode Brownian oscillator model. The first two low-lying excited-states of POA 6 were found to exhibit excitation characteristics spanning entire conjugated backbone despite the presence of antiaromatic phenylene section. Absorption and fluorescence spectra calculated from both time-dependent density functional theory and multimode Brownian oscillator model are shown to reach good agreement with experimental ones. The coupling between phonon modes and optical transitions is generally weak as suggested by the multimode Brownian oscillator model. Broader peaks of POA 6 spectra are found to relate to stronger coupling between low frequency phonon modes such as backbone twisting (with frequency <300 cm(-1)) and optical transitions. Furthermore, POA 6 exhibits weaker exciton-phonon coupling for the phonon modes above 1000 cm(-1) compared to TIPS-anthracene owing to extended conjugated backbone. A significant coupling between an in-plane breathing mode localized around the antiaromatic phenylene segment with frequency at 1687 cm(-1) and optical transitions for the first two excited-states of POA 6 is also observed. PMID:26611665
NASA Astrophysics Data System (ADS)
Yuan, Jian-Hui; Zhang, Yan; Guo, Xinxia; Zhang, Jinjin; Mo, Hua
2015-04-01
Using the configuration-integration method, we investigated theoretically the low-lying states and optical absorption properties of a hydrogenic impurity in a parabolic quantum dot modulation by applied electric field. The low-lying states and optical absorption properties depend sensitively on the electric field F and the strength of the parabolic confinement ℏω0 . We discuss the linear and third-order nonlinear optical absorption coefficients of the dot (i) with the impurity ion and (ii) without the impurity ion. In the first case, the increase of the parabolic confinement ℏω0 (or the electric field F) can induce the blueshift (or redshift) of the peak of the absorption coefficient. Also the optical intensity can induce the increase of the third-order nonlinear optical absorption coefficients to weaken and even bleach the total optical absorption coefficients. Similar behavior has also been observed in the second case, but there is no redshift of the peak positions of the absorption coefficient with the increase of the electric field F. Compared with the second case, it is easily seen that there are the blueshifts of the peak of the absorption coefficients, which can be used as a technical means for detecting impurities.
NASA Astrophysics Data System (ADS)
Gatos, I.; Tsantis, S.; Karamesini, M.; Skouroliakou, A.; Kagadis, G.
2015-09-01
Purpose: The design and implementation of a computer-based image analysis system employing the support vector machine (SVM) classifier system for the classification of Focal Liver Lesions (FLLs) on routine non-enhanced, T2-weighted Magnetic Resonance (MR) images. Materials and Methods: The study comprised 92 patients; each one of them has undergone MRI performed on a Magnetom Concerto (Siemens). Typical signs on dynamic contrast-enhanced MRI and biopsies were employed towards a three class categorization of the 92 cases: 40-benign FLLs, 25-Hepatocellular Carcinomas (HCC) within Cirrhotic liver parenchyma and 27-liver metastases from Non-Cirrhotic liver. Prior to FLLs classification an automated lesion segmentation algorithm based on Marcov Random Fields was employed in order to acquire each FLL Region of Interest. 42 texture features derived from the gray-level histogram, co-occurrence and run-length matrices and 12 morphological features were obtained from each lesion. Stepwise multi-linear regression analysis was utilized to avoid feature redundancy leading to a feature subset that fed the multiclass SVM classifier designed for lesion classification. SVM System evaluation was performed by means of leave-one-out method and ROC analysis. Results: Maximum accuracy for all three classes (90.0%) was obtained by means of the Radial Basis Kernel Function and three textural features (Inverse- Different-Moment, Sum-Variance and Long-Run-Emphasis) that describe lesion's contrast, variability and shape complexity. Sensitivity values for the three classes were 92.5%, 81.5% and 96.2% respectively, whereas specificity values were 94.2%, 95.3% and 95.5%. The AUC value achieved for the selected subset was 0.89 with 0.81 - 0.94 confidence interval. Conclusion: The proposed SVM system exhibit promising results that could be utilized as a second opinion tool to the radiologist in order to decrease the time/cost of diagnosis and the need for patients to undergo invasive examination.
Theoretical spectroscopy study of the low-lying electronic states of UX and UX^{+}, X = F and Cl
Bross, David H.; Peterson, Kirk A.
2015-11-13
Spectroscopic constants (T_{e}, r_{e}, B_{0}, ω_{e}, ω_{e}x_{e}) have been calculated for the low-lying electronic states of UF, UF^{+}, UCl, and UCl^{+} using complete active space 2nd-order perturbation theory (CASPT2), with a series of correlation consistent basis sets. The latter included those based on both pseudopotential (PP) and all-electron Douglas-Kroll-Hess (DK) Hamiltonians for the U atom. Spin orbit effects were included a posteri using the state interacting method using both PP and Breit Pauli (BP) operators, as well as from exact two-component (X2C) methods for U^{+} and UF^{+}. Complete basis set (CBS) limits were obtained by extrapolation where possible and the PP and BP calculations were compared at their respective CBS limits. The PP-based method was shown to be reliable in calculating spectroscopic constants, in particular when using the state interacting method with CASPT2 energies (SO-CASPT2). The two component calculations were limited by computational resources and could not include electron correlation from the nominally closed shell 6s and 6p orbitals of U. UF and UCl were both calculated to have Ω=9/2 ground states. The first excited state of UCl was calculated to be an Ω=7/2 state at 78 cm^{-1} as opposed to the same state at 435 cm-1 in UF, and the other low-lying states of UCl showed a similar compression relative to UF. Likewise UF+ and UCl+ both have Ω=4 ground states and the manifold of low-lying excited Ω = 3, 2, 1, 0 states were energetically closer together in UCl^{+} than in UF^{+}, ranging up to 776 cm^{-1} in UF^{+} and only 438 cm^{-1} in UCl^{+}. As in previous research, the final PP-based SO-CASPT2 results for UF^{+} and UF agree well with experiment, and are expected to be predictive for UCl and UCl^{+}, which are reported here for the first time.
NASA Astrophysics Data System (ADS)
Miyashita, Yuji; Ouchi, Hiroyuki; Izumi, Sayaka; Sasaki, Ayako; Sato, Nozomi; Tateoka, Miki; Hoshino, Sayo; Nagano, Tetsuya; Yamashita, Wataru; Yamazaki, Akiyoshi; Shimada, Kenzi; Ishida, Takashi; Wakui, Takashi; Shinozuka, Tsutomu; Tanigaki, Minoru
2009-10-01
To extend the studies on neutron-rich nuclei, we have developed an RF-IGISOL technique, which is combination of the gas catcher technique and the electrical field guiding technique with a large volume gas cell. As the first step to such approach, we are planning and trying the systematic measurement of g-factor in the neutron rich nuclei extracted as an radioactive beam from our RF-IGISOL at Tohoku University. The g-factor measurement for the low-lying state of ^109Rh (Ex = 225.98 keV, T1/2 = 1.66 μs) is the first on-line experiment with our RF-IGISOL system. The g-factor for this state has been determined to be g = 0.78 ^+0.17-0.03 μN by the on-line TDPAC method. In this contribution, the details of experimental results will be reported.
NASA Astrophysics Data System (ADS)
Marwa, N. El-Hammamy
2015-03-01
The experimental data on elastic and inelastic scattering of 270 MeV 3He particles to several low lying states in 90Zr, 116Sn and 208Pb are analyzed within the double folding model (DFM). Fermi density distribution (FDD) of target nuclei is used to obtain real potentials with different powers. DF results are introduced into a modified DWUCK4 code to calculate the elastic and inelastic scattering cross sections. Two choices of potentials form factors are used; Woods Saxon (WS) and Woods Saxon Squared (WS2) for real potential, while the imaginary part is taken as phenomenological Woods Saxon (PWS) and phenomenological Woods Saxon Squared (PWS2). This comparison provides information about the similarities and differences of the models used in calculations.
Xie Wenfang
2013-01-31
Optical absorptions of the low-lying states with higher angular momenta of the D{sup -} system in a spherical quantum dot (QD) with the Gaussian potential are studied by using the matrix diagonalisation method and the compact density-matrix approach. The linear, nonlinear third-order and total optical absorption coefficients are calculated for the {sup 1}P{sup -} {yields} {sup 1}D{sup +} and {sup 1}D{sup +} {yields} {sup 1}F{sup -} transitions. Numerical results for GaAs/Ga{sub 1-x}Al{sub x}As QDs are presented. The calculated results show that with increasing quantum numbers describing the angular momenta of transitions the optical absorption peaks shift towards lower energies and their intensities increase. (quantum dots)
NASA Astrophysics Data System (ADS)
Etilé, A.; Verney, D.; Arsenyev, N. N.; Bettane, J.; Borzov, I. N.; Cheikh Mhamed, M.; Cuong, P. V.; Delafosse, C.; Didierjean, F.; Gaulard, C.; Van Giai, Nguyen; Goasduff, A.; Ibrahim, F.; Kolos, K.; Lau, C.; Niikura, M.; Roccia, S.; Severyukhin, A. P.; Testov, D.; Tusseau-Nenez, S.; Voronov, V. V.
2015-06-01
The β decay of 82Ge Ge was re-investigated using the newly commissioned tape station BEDO at the electron-driven ISOL (isotope separation on line) facility ALTO operated by the Institut de Physique Nucléaire, Orsay. The original motivation of this work was focused on the sudden occurrence in the light N =49 odd-odd isotonic chain of a large number of J ≤1 states (positive or negative parity) in 80Ga by providing a reliable intermediate example, viz., 82As. The extension of the 82As level scheme towards higher energies from the present work has revealed three potential 1+ states above the already known one at 1092 keV. In addition our data allow ruling out the hypothesis that the 843 keV level could be a 1+ state. A detailed analysis of the level scheme using both an empirical core-particle coupling model and a fully microscopic treatment within a Skyrme-QRPA (quasiparticle random-phase approximation) approach using the finite-rank separable approximation was performed. From this analysis two conclusions can be drawn: (i) the presence of a large number of low-lying low-spin negative parity states is due to intruder states stemming from above the N =50 shell closure, and (ii) the sudden increase, from 82As to 80Ga, of the number of low-lying 1+ states and the corresponding Gamow-Teller fragmentation are naturally reproduced by the inclusion of tensor correlations and couplings to 2p-2h excitations.
NASA Astrophysics Data System (ADS)
Garzon, E. J.; Oset, E.
2015-02-01
We study the meson-baryon interaction with JP=1 /2- using the hidden-gauge Lagrangians and mixing pseudoscalar meson-baryon with the vector meson-baryon states in a coupled channels scheme with π N ,η N ,K Λ ,K Σ ,ρ N , and π Δ (d wave). We fit the subtraction constants of each channel to the S11 partial wave amplitude of the π N scattering data extracted from the partial wave analysis of the George Washington group. We find two poles that we associate to the N*(1535 ) and the N*(1650 ) resonances, with negative subtraction constants of natural size, and compare the results with empirical determinations of these pole positions. We calculate the branching ratios for the different channels of each resonance and we find a good agreement with the experimental data. The cross section for the π-p →η n scattering is also evaluated and compared with experiment.
Biselli, A. S.; Burkert, V. D.; Avakian, H.; Boiarinov, S.; Bosted, P.; Carman, D. S.; Degtyarenko, P. V.; Deur, A.; Egiyan, H.; Elouadrhiri, L.; Guo, L.; Gyurjyan, V.; Ito, M. M.; Kubarovsky, V.; Laget, J. M.; Mecking, B. A.; Mestayer, M. D.; Niczyporuk, B. B.; Nozar, M.; Sapunenko, V.
2008-10-15
The exclusive channel p-vectore-vector,e{sup '}p){pi}{sup 0} was studied in the first and second nucleon resonance regions in the Q{sup 2} range from 0.187 to 0.770 GeV{sup 2} at Jefferson Lab using the CEBAF Large Acceptance Spectrometer. Longitudinal target and beam-target asymmetries were extracted over a large range of center-of-mass angles of the {pi}{sup 0} and compared to the unitary isobar model MAID, the dynamic model by Sato and Lee, and the dynamic model DMT. A strong sensitivity to individual models was observed, in particular for the target asymmetry and in the higher invariant mass region. This data set, once included in the global fits of the above models, is expected to place strong constraints on the electrocoupling amplitudes A{sub 1/2} and S{sub 1/2} for the Roper resonance N(1400)P{sub 11} and the N(1535)S{sub 11} and N(1520)D{sub 13} states.
Boucher, Yan; Orata, Fabini D.; Alam, Munirul
2015-01-01
Cholera is a diarrheal disease that has changed the history of mankind, devastating the world with seven pandemics from 1817 to the present day. Although there is little doubt in the causative agent of these pandemics being Vibrio cholerae of the O1 serogroup, where, when, and how this pathogen emerged is not well understood. V. cholerae is a ubiquitous coastal species that likely existed for tens of thousands of years. However, the evolution of a strain capable of causing a large-scale epidemic is likely more recent historically. Here, we propose that the unique human and physical geography of low-lying river deltas made it possible for an environmental bacterium to evolve into a deadly human pathogen. Such areas are often densely populated and salt intrusion in drinking water frequent. As V. cholerae is most abundant in brackish water, its favored environment, it is likely that coastal inhabitants would regularly ingest the bacterium and release it back in the environment. This creates a continuous selection pressure for V. cholerae to adapt to life in the human gut. PMID:26539168
NASA Astrophysics Data System (ADS)
Meo, F. Di; Trouillas, P.; Adamo, C.; Sancho-García, J. C.
2013-10-01
The present work assesses some recently developed double-hybrid density functionals (B2π-PLYP, PBE0-DH, and PBE0-2) using linear-response Tamm-Dancoff Time-Dependent Density Functional Theory. This assessment is achieved against experimentally derived low-lying excitation energies of large organic dyes of recent interest, including some excitations dominated by charge-transfer transitions. Comparisons are made with some of the best-performing methods established from the literature, such as PBE0 or B3LYP hybrid or the recently proposed B2-PLYP and B2GP-PLYP double-hybrid models, to ascertain their quality and robustness on equal footing. The accuracy of parameter-free or empirical forms of double-hybrid functionals is also briefly discussed. Generally speaking, it turns out that double-hybrid expressions always provide more accurate estimates than corresponding hybrid methods. Double-hybrid functionals actually reach averaged accuracies of 0.2 eV, that can be admittedly considered close to any intended accuracy limit within the present theoretical framework.
NASA Astrophysics Data System (ADS)
Guo, Jiangang; Yamaura, Jun-ichi; Lei, Hechang; Matsuishi, Satoru; Qi, Yanpeng; Hosono, Hideo
2013-10-01
We report on new superconductors Ban+2Ir4nGe12n+4 (n = 1, 2) with critical temperatures Tc = 6.1 and 3.2 K, respectively, along with their crystal structures, electron transport, and specific heat. The compounds are composed of alternating Ba@Ir8Ge16 and Ba@Ir2Ge16 cages, both of which are larger in the n = 1 sample than in the n = 2 sample. The normal-state heat capacity reveals two low-lying vibration modes associated with guest Ba cations, and both characteristic temperatures in Ba3Ir4Ge16 are smaller than those in Ba4Ir8Ge28. Meanwhile, the density functional theory calculations reveal that the Ge-4p bands dominated the Fermi level in both samples. We propose that the softening of localized phonons due to expansion of the cage strengthens the electron-phonon coupling between Ba cations and Ge anions, leading to the higher Tc in Ba3Ir4Ge16.
NASA Astrophysics Data System (ADS)
Shiga, Y.; Yoneda, K.; Steppenbeck, D.; Aoi, N.; Doornenbal, P.; Lee, J.; Liu, H.; Matsushita, M.; Takeuchi, S.; Wang, H.; Baba, H.; Bednarczyk, P.; Dombradi, Zs.; Fulop, Zs.; Go, S.; Hashimoto, T.; Honma, M.; Ideguchi, E.; Ieki, K.; Kobayashi, K.; Kondo, Y.; Minakata, R.; Motobayashi, T.; Nishimura, D.; Otsuka, T.; Otsu, H.; Sakurai, H.; Shimizu, N.; Sohler, D.; Sun, Y.; Tamii, A.; Tanaka, R.; Tian, Z.; Tsunoda, Y.; Vajta, Zs.; Yamamoto, T.; Yang, X.; Yang, Z.; Ye, Y.; Yokoyama, R.; Zenihiro, J.
2016-02-01
The low-lying level structures of nuclei in the vicinity of 78Ni were investigated using in-beam γ -ray spectroscopy to clarify the nature of the nuclear magic numbers Z =28 and N =50 in systems close to the neutron drip line. Nucleon knockout reactions were employed to populate excited states in 80Zn and 82Zn. A candidate for the 41+ level in 80Zn was identified at 1979(30) keV, and the lifetime of this state was estimated to be 136-67+92 ps from a line-shape analysis. Moreover, the energy of the 21+ state in 82Zn is reported to lie at 621(11) keV. The large drop in the 21+ energy at 82Zn indicates the presence of a significant peak in the E (21+) systematics at N =50 . Furthermore, the E (41+) /E (21+) and B (E 2 ;41+→21+) /B (E 2 ;21+→0g.s . +) ratios in 80Zn were deduced to be 1.32 (3 ) and 1 .12-60+80 , respectively. These results imply that 80Zn can be described in terms of two-proton configurations with a 78Ni core and are consistent with a robust N =50 magic number along the Zn isotopic chain. These observations, therefore, indicate a persistent N =50 shell closure in nuclei far from the line of β stability, which in turn suggests a doubly magic structure for 78Ni.
NASA Astrophysics Data System (ADS)
Koh, Yang Wei
2016-04-01
We present an extensive numerical study of the Sherrington-Kirkpatrick model in a transverse field. Recent numerical studies of quantum spin glasses have focused on exact diagonalization of the full Hamiltonian for small systems (≈20 spins). However, such exact numerical treatments are difficult to apply on larger systems. We propose making an approximation by using only a subspace of the full Hilbert space spanned by low-lying excitations consisting of one-spin-flipped and two-spin-flipped states. The approximation procedure is carried out within the theoretical framework of the Hartree-Fock approximation and configuration interaction. Although not exact, our approach allows us to study larger system sizes comparable to that achievable by state-of-the-art quantum Monte Carlo simulations. We calculate two quantities of interest due to recent advances in quantum annealing, the ground-state energy and the energy gap between the ground and first excited states. For the energy gap, we derive a formula that enables it to be calculated using just the ground-state wave function, thereby circumventing the need to diagonalize the Hamiltonian. We calculate the scalings of the energy gap and the leading correction to the extensive part of the ground-state energy with system size, which are difficult to obtain with current methods.
Pepper, Mitzy; Ho, Simon Y W; Fujita, Matthew K; Scott Keogh, J
2011-12-01
It is a widely held assumption that populations historically restricted to mountain refugia tend to exhibit high levels of genetic diversity and deep coalescent histories, whereas populations distributed in surrounding low-lying regions tend to be genetically depauperate following recent expansion from refugia. These predicted genetic patterns are based largely on our understanding of glaciation history in Northern Hemisphere systems, yet remain poorly tested in analogous Southern Hemisphere arid systems because few examples in the literature allow the comparison of widespread taxa distributed across mountain and desert biomes. We demonstrate with multiple datasets from Australian geckos that topographically complex mountain regions harbor high nucleotide diversity, up to 18 times higher than that of the surrounding desert lowlands. We further demonstrate that taxa in topographically complex areas have older coalescent histories than those in the geologically younger deserts, and that both ancient and more recent aridification events have contributed to these patterns. Our results show that, despite differences in the details of climate and landscape changes that occurred in the Northern and Southern hemispheres (ice-sheets versus aridification), similar patterns emerge that illustrate the profound influence of the Pleistocene on contemporary genetic structure. PMID:21871574
NASA Astrophysics Data System (ADS)
Karamanis, P.; Marchal, R.; Carbonnierre, P.; Pouchan, C.
2012-12-01
The (hyper)polarizabilities of the global minima and of low lying isomers of ground doped aluminum clusters of the AlSin type (n=3-9) have been studied within the density functional framework. Our results show that the polarizabilities and first hyperpolarizabilities per atom of these doped Al doped clusters rabidly degrease with the cluster size. Also by tracing a significant number of stable low lying isomers we demonstrate that both the average values of the mean polarizabilities per atom and of the total fist hyperpolarizabilities of those species follow closely the evolution that is observed in the case of their ground state structures.
NASA Astrophysics Data System (ADS)
Zu, Dong-Lin; Guo, Hua; Song, Xiao-Yu; Bao, Shang-Lian
2002-10-01
The approach of expanding the magnetic scalar potential in a series of Legendre polynomials is suitable for designing a conventional superconducting magnetic resonance imaging magnet of distributed solenoidal configuration. Whereas the approach of expanding the magnetic vector potential in associated Legendre harmonics is suitable for designing a single-solenoid magnet that has multiple tiers, in which each tier may have multiple layers with different winding lengths. A set of three equations to suppress some of the lowest higher-order harmonics is found. As an example, a 4T single-solenoid magnetic resonance imaging magnet with 4×6 layers of superconducting wires is designed. The degree of homogeneity in the 0.5m diameter sphere volume is better than 5.8 ppm. The same degree of homogeneity is retained after optimal integralization of turns in each correction layer. The ratio Bm/B0 in the single-solenoid magnet is 30% lower than that in the conventional six-solenoid magnet. This tolerates higher rated superconducting current in the coil. The Lorentz force of the coil in the single-solenoid system is also much lower than in the six-solenoid system. This novel type of magnet possesses significant advantage over conventional magnets, especially when used as a super-high field functional magnetic resonance imaging magnet.
Luk'yanchuk, B. S.; Ternovsky, V.
2006-06-15
We analyze the energy flow during the scattering of a plane wave by a small homogeneous cylinder in the vicinity of surface-plasmon resonance, where {epsilon}{sup '}=Re {epsilon}=-1 ({epsilon} stands for permittivity). For the case of small dissipation, {epsilon}{sup ''}=Im {epsilon}<<1, this scattering can strongly deviate from the classical dipole approximation (Rayleigh scattering). In certain specified cases, the Rayleigh scattering is replaced with an anomalous light scattering regardless the wire smallness. The phenomenon is based on interplay of the usual dissipative and radiative damping, where the latter is related to inverse transformation of localized resonant plasmons into scattered light. The anomalous light scattering possesses a variety of unusual features, such as an inverse hierarchy of optical resonances and a complicated near-field structure, which may include optical vortexes, optical whirlpools, and other peculiarities in nanoscale area.
NASA Astrophysics Data System (ADS)
Li, Xia; Zhang, Xiaomei; Yan, Bing
2015-05-01
Ab initio calculations have been performed on the low-lying excited and ground states of PH+. The potential energy curves (PECs) of the Λ-S states were calculated with multi-reference configuration interaction (MRCI) method along with the basis sets at 5-ξ level. In order to improve the PECs, the Davidson(+Q) correction and the Scalar relativistic effect are included. The corresponding spectroscopic constants were determined and good agreements with the available measurement were found. The interactions of the A2Δ-4Π and 12Σ+-4Π by the spin-orbit coupling (SOC) effect were well described by the spin-orbit matrix elements. The SOC effect makes the original 8 Λ-S states split into 15 Ω states. The Ω = 1/2 state generated from the X2Π state is confirmed to the ground Ω state. And the SOC splitting for the X2Π is calculated to be 294 cm-1. The SOC effect has large effect on the PECs of the A2Δ and 12Σ+ states, leading to much more shallow potential wells as well as potential barriers. The analysis of the wavefunction for the Ω states shows that the strong spin-orbit interaction exists near the crossing points of the PECs for the Λ-S states. The transition dipole moments (TDMs) of transitions A2Δ-X2Π and 12Σ--X2Π are evaluated with the MRCI wavefunction. Based on the TDMs along with the calculated Franck-Condon factors, the radiative lifetimes for the selected vibrational levels of A2Δ and 12Σ- states are predicted at the microseconds (μs). Good agreement with the measurement shows that the lowest vibrational level for A2Δ state is almost uninfluenced by the perturbation via the SOC effect.
NASA Astrophysics Data System (ADS)
Lee, Edmond P. F.; Mok, Daniel K. W.; Chau, Foo-tim; Dyke, John M.
2006-09-01
Geometry optimization calculations were carried out on the X˜A11 state of SF2 and the X˜B12, ÃA12, B˜B22, C˜B22, D˜A12, and ẼA22 states of SF2+ employing the restricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] method and basis sets of up to the augmented correlation-consistent polarized quintuple-zeta [aug-cc-pV(5+d )Z] quality. Effects of core electron (S 2s22p6 and F 1s2 electrons) correlation and basis set extension to the complete basis set limit on the computed minimum-energy geometries and relative electronic energies (adiabatic and vertical ionization energies) were investigated. RCCSD(T) potential energy functions (PEFs) were calculated for the X˜A11 state of SF2 and the low-lying states of SF2+ listed above employing the aug-cc-pV(5+d )Z and aug-cc-pV5Z basis sets for S and F, respectively. Anharmonic vibrational wave functions of these neutral and cationic states of SF2, and Franck-Condon (FC) factors of the lowest four one-electron allowed neutral photoionizations were computed employing the RCCSD(T) PEFs. Calculated FC factors with allowance for Duschinsky rotation and anharmonicity were used to simulate the first four photoelectron bands of SF2. The agreement between the simulated and observed first bands in the HeI photoelectron spectrum reported by de Leeuw et al. [Chem. Phys. 34, 287 (1978)] is excellent. Our calculations largely support assignments made by de Leeuw et al. on the higher ionization energy bands of SF2.
Li, Xia; Zhang, Xiaomei; Yan, Bing
2015-05-01
Ab initio calculations have been performed on the low-lying excited and ground states of PH(+). The potential energy curves (PECs) of the Λ-S states were calculated with multi-reference configuration interaction (MRCI) method along with the basis sets at 5-ξ level. In order to improve the PECs, the Davidson(+Q) correction and the Scalar relativistic effect are included. The corresponding spectroscopic constants were determined and good agreements with the available measurement were found. The interactions of the A(2)Δ-(4)Π and 1(2)Σ(+)-(4)Π by the spin-orbit coupling (SOC) effect were well described by the spin-orbit matrix elements. The SOC effect makes the original 8 Λ-S states split into 15Ω states. The Ω=1/2 state generated from the X(2)Π state is confirmed to the ground Ω state. And the SOC splitting for the X(2)Π is calculated to be 294cm(-1). The SOC effect has large effect on the PECs of the A(2)Δ and 1(2)Σ(+) states, leading to much more shallow potential wells as well as potential barriers. The analysis of the wavefunction for the Ω states shows that the strong spin-orbit interaction exists near the crossing points of the PECs for the Λ-S states. The transition dipole moments (TDMs) of transitions A(2)Δ-X(2)Π and 1(2)Σ(-)-X(2)Π are evaluated with the MRCI wavefunction. Based on the TDMs along with the calculated Franck-Condon factors, the radiative lifetimes for the selected vibrational levels of A(2)Δ and 1(2)Σ(-) states are predicted at the microseconds (μs). Good agreement with the measurement shows that the lowest vibrational level for A(2)Δ state is almost uninfluenced by the perturbation via the SOC effect. PMID:25688687
NASA Astrophysics Data System (ADS)
Barker, Beau; Meyer, Edmund; Schacht, Mike; Collins, Lee; Wilkerson, Marianne; Zhao, Xinxin
2016-05-01
The low-lying (7.8 eV) isomeric state in 229 Th has the potential to become a nuclear frequency standard. 229 Th recoils from 233 U decays have been collected in MgF2 for use in the direct search of the transition. Of interest is the oxidation state of the implanted 229 Th atoms as this can have an influence on the decay mechanisms and photon emission rate. Too determine the oxidation state of the implanted 229 Th recoils we have employed laser induced florescence (LIF), and plan-wave pseudopotential DFT calculations to search for emission from thorium ions in oxidation states less than + 4. Our search focused on detecting emission from Th3+ ions. The DFT calculations predicted the Th3+ state to be the most likely to be present in the crystal after Th4+. We also calculated the band structure for the Th3+ doped MgF2 crystal. For LIF spectra a number of excitation wavelengths were employed, emission spectra in the visible to near-IR were recorded along with time-resolved emission spectra. We have found no evidence for Th3+ in the MgF2 plates. We also analyzed the detection limit of our apprentice and found that the minimum number of Th3+ atoms that we could detect is quite small compared to the number of implanted 229 Th recoils. The number of implanted 229 Th recoils was derived from a γ-ray spectrum by monitoring emission from the daughters of 228 Th. These were present in the MgF2 plates due to a 232 U impurity, which decays to 228 Th, in the source. LA-UR-16-20442.
NASA Astrophysics Data System (ADS)
Chattopadhyay, Anjan
2012-02-01
Ab initio-based configuration interaction studies on RbHe and He-Rb-He have explored some key features of the low-lying electronic states of these van der Waals systems. The radiative lifetime of the Rb*He exciplex has been calculated to be around 24.5 ns, which is slightly higher than the HeRb*He lifetime (˜20 ns) and lower than the atomic fluorescence lifetime of Rb, by roughly 3.5 ns. Better exciplex stability of the symmetric triatomic system is evidenced by its higher binding energy value in comparison to the diatomic system by a substantial margin. BSSE-corrected spin-orbit calculations of RbHe have predicted a potential barrier of the 12Π1/2 state with a height of 15 cm-1 and width of 2.57 Å. The 2Πu state of the triatomic molecule shows a conical intersection of its Renner-Teller components (12A1 and 12B2) near a 99° bond angle along the bending path. Their unstable higher excited states (12Σ+1/2 or 12Σ+g,1/2) can trigger the pumping of the blue side of the ns2S1/2 → np2P3/2 transition, and this may eventually lead to the np2P1/2 →ns2S1/2 lasing transition. The broad fluorescence band with a peak near 11 900 cm-1 is found to arise from the 12Π3/2-X2Σ+1/2 transition of RbHe.
Peterson, Kirk A.; Francisco, Joseph S.
2014-01-28
A systematic ab initio treatment of the nitryl halides (XNO{sub 2}) and the cis- and trans- conformers of the halide nitrites (XONO), where X = Cl, Br, and I, have been carried out using highly correlated methods with sequences of correlation consistent basis sets. Equilibrium geometries and harmonic frequencies have been accurately calculated in all cases at the explicitly correlated CCSD(T)-F12b level of theory, including the effects of core-valence correlation for the former. Where experimental values are available for the equilibrium structures (ClNO{sub 2} and BrNO{sub 2}), the present calculations are in excellent agreement; however, the X-O distances are slightly too long by about 0.01 Å due to missing multireference effects. Accurate predictions for the iodine species are made for the first time. The vertical electronic excitation spectra have been calculated using equation-of-motion coupled cluster methods for the low-lying singlet states and multireference configuration interaction for both singlet and triplet states. The latter also included the effects of spin-orbit coupling to provide oscillator strengths for the ground state singlet to excited triplet transitions. While for ClNO{sub 2} the transitions to excited singlet states all occur at wavelengths shorter than 310 nm, there is one longer wavelength singlet transition in BrNO{sub 2} and two in the case of INO{sub 2}. The long wavelength tail in the XNO{sub 2} species is predicted to be dominated by transitions to triplet states. In addition to red-shifting from X = Cl to I, the triplet transitions also increase in oscillator strength, becoming comparable to many of the singlet transitions in the case of INO{sub 2}. Hence in particular, the latter species should be very photolabile. Similar trends are observed and reported for the halogen nitrites, many of which for the first time.
NASA Astrophysics Data System (ADS)
Perozzi, E.; Murdin, P.
2000-11-01
A resonance in CELESTIAL MECHANICS occurs when some of the quantities characterizing the motion of two or more celestial bodies can be considered as commensurable, i.e. their ratio is close to an integer fraction. In a simplified form, this can be expressed as ...
NASA Astrophysics Data System (ADS)
Hemakumara, GPTS; Rainis, Ruslan
2015-02-01
Living in Low-lying areas is a challenging task, but due to the lack of suitable land at affordable prices, thousands of householders have been establishing their own houses on Low-lying areas. Manipulation and conversion of low lying areas have led to an increase in the frequency and severity of micro disasters because the cumulative effect of these settlements is very high. Therefore, it is needed to examine how individual households have been emerging in Low-lying areas. This process is primarily influenced and controlled by Socio-economic factors. In the field survey conducted for this study, 388 householders were interviewed face to face to obtain the primary data. Collected data were applied to the Multivariate binary logistic Model. The Dependent variable of the model was set as Stable Houses and Non-Stable Houses based on the weighted values that were obtained from the field observations. Independent variables of this study are nine key aspects of the socio-economic conditions in these areas. Units of analysis of the study were taken as individual housing plots in the study area. The particular combination of Socio-Economic factors that exerted influence on each housing plot was measured using predicted probability value of logistic model and linked it with GIS land plot's map. Accuracy of Final Model is 86.9 % and probability level of influencing factors given a clear idea about household distribution and status while providing guidance about how the planning authorities should monitor and manage low lying areas, taking into consideration the present housing condition of these areas.
NASA Astrophysics Data System (ADS)
Mok, Daniel K. W.; Chau, Foo-tim; Lee, Edmond P. F.; Dyke, John M.
2006-09-01
Geometry optimization calculations were carried out on the X˜A11 state of SCl2 and the X˜B12, ÃB22, B˜A12, C˜A12, D˜A22, and ẼB22 states of SCl2+ at the restricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] level with basis sets of up to the augmented correlation-consistent polarized quintuple-zeta [aug-cc-pV(5+d )Z] quality. Effects of core electron correlation, basis set extension to the complete basis set limit, and relativistic contributions on computed minimum-energy geometrical parameters and/or relative electronic energies were also investigated. RCCSD(T) potential energy functions (PEFs) were calculated for the X˜A11 state of SCl2 and the low-lying states of SCl2+ listed above employing the aug-cc-pV(5+d )Z basis set. Anharmonic vibrational wave functions of these neutral and cationic states of SCl2, and Franck-Condon (FC) factors of the lowest four one-electron allowed neutral photoionizations were computed employing the RCCSD(T )/aug-cc-pV(5+d)Z PEFs. Calculated FC factors with allowance for the Duschinsky rotation and anharmonicity were used to simulate the first four photoelectron (PE) bands of SCl2. The agreement between simulated and observed He I PE spectra reported by Colton et al. [J. Electron Spectrosc. Relat. Phenom. 3, 345 (1974)] and Solouki et al. [Chem. Phys. Lett. 26, 20 (1974)] is excellent. However, our FC spectral simulations indicate that the first observed vibrational component in the first PE band of SCl2 is a "hot" band arising from the SCl2+X˜B12(0,0,0)←SCl2X˜A11(1,0,0) ionization. Consequently, the experimental adiabatic ionization energy of SCl2 is revised to 9.55±0.01eV, in excellent agreement with results obtained from state-of-the-art ab initio calculations in this work.
NASA Astrophysics Data System (ADS)
Wu, Dong-lan; Tan, Bin; Wen, Yu-feng; Zeng, Xue-feng; Xie, An-dong; Yan, Bing
2016-05-01
Accurate theoretical calculations on the MgBr radical have been carried out by using the high-level relativistic multireference configuration interaction method with Davidson correction (MRCI + Q) using correlation-consistent Quintuple-ζ quality basis set. The potential energy curves (PECs) of the 14 Λ-S states of MgBr have been computed. In order to improve the PECs, the core-valence correlation, scalar relativistic effect, and spin-orbit coupling effect are taken into account in the computations. The spectroscopic constants of the bound states have been determined from the computed PECs. The results of the ground state X2Σ+ and the first excited state A2Π are in good agreement with those from the available experiments, while spectroscopic constants of the other electronic states are firstly reported. The low-lying ion-pair state B2Σ+ correlated to ion-pair dissociation limit Mg+ (2Sg) + Br- (1Sg) is characterized. The permanent dipole moments (PDMs) of Λ-S states and the R-dependent spin-orbit (SO) matrix elements are computed. The results indicate that the abrupt changes of PDMs and the SO matrix elements are attributed to the changes of the electronic configurations near the avoided crossing point. After taking the SOC effect into account, the 14 Λ-S states split into 30 Ω states, and the SOC splitting for the A2Π is calculated to be 102.58 cm- 1. The SOC effect, leading to the double-well potential of the Ω = (3)1/2 state, is found to be substantial for MgBr. In order to further illustrate the SOC effect and the avoided crossing phenomenon of the PECs, the Λ-S compositions in the Ω state wavefunctions are analyzed in detail. Finally, the transition dipole moments (TDMs) of several transitions from upper Ω states to the ground X2Σ+1/2 state and the corresponding radiative lifetimes have been studied. It is shown that the (1)3/2-X2Σ+1/2 and (2)3/2-X2Σ+1/2 are particularly important to the observed transitions A2Π-X2Σ+ and C2Π-X2Σ+. The
Wu, Dong-Lan; Tan, Bin; Wen, Yu-Feng; Zeng, Xue-Feng; Xie, An-Dong; Yan, Bing
2016-05-15
Accurate theoretical calculations on the MgBr radical have been carried out by using the high-level relativistic multireference configuration interaction method with Davidson correction (MRCI+Q) using correlation-consistent Quintuple-ζ quality basis set. The potential energy curves (PECs) of the 14 Λ-S states of MgBr have been computed. In order to improve the PECs, the core-valence correlation, scalar relativistic effect, and spin-orbit coupling effect are taken into account in the computations. The spectroscopic constants of the bound states have been determined from the computed PECs. The results of the ground state X(2)Σ(+) and the first excited state A(2)Π are in good agreement with those from the available experiments, while spectroscopic constants of the other electronic states are firstly reported. The low-lying ion-pair state B(2)Σ(+) correlated to ion-pair dissociation limit Mg(+) ((2)Sg)+Br(-) ((1)Sg) is characterized. The permanent dipole moments (PDMs) of Λ-S states and the R-dependent spin-orbit (SO) matrix elements are computed. The results indicate that the abrupt changes of PDMs and the SO matrix elements are attributed to the changes of the electronic configurations near the avoided crossing point. After taking the SOC effect into account, the 14 Λ-S states split into 30Ω states, and the SOC splitting for the A(2)Π is calculated to be 102.58cm(-1). The SOC effect, leading to the double-well potential of the Ω=(3)1/2 state, is found to be substantial for MgBr. In order to further illustrate the SOC effect and the avoided crossing phenomenon of the PECs, the Λ-S compositions in the Ω state wavefunctions are analyzed in detail. Finally, the transition dipole moments (TDMs) of several transitions from upper Ω states to the ground X(2)Σ(+)1/2 state and the corresponding radiative lifetimes have been studied. It is shown that the (1)3/2-X(2)Σ(+)1/2 and (2)3/2-X(2)Σ(+)1/2 are particularly important to the observed transitions A(2)Π-X(2)
ERIC Educational Resources Information Center
Roche, John
1997-01-01
Suggests an approach to teaching vectors that promotes active learning through challenging questions addressed to the class, as opposed to subtle explanations. Promotes introducing vector graphics with concrete examples, beginning with an explanation of the displacement vector. Also discusses artificial vectors, vector algebra, and unit vectors.…
Low-lying {sup 3}P{sup o} and {sup 3}S{sup e} states of Rb{sup -}, Cs{sup -}, and Fr{sup -}
Bahrim, C.; Thumm, U.
2000-02-01
Our Dirac R-matrix calculations suggest that none of the heavy alkali-metal negative ions, Rb, Cs, and Fr, has an excited bound state. Their lowest excited state appears to be a multiplet of {sup 3}P{sub J}{sup o}-shape resonances, the J=1 component of which was recently observed in photodetachment experiments on Cs{sup -}. We analyze these {sup 3}P{sub J}{sup o} and the {sup 3}S{sup e} excited negative ion states in partial and converged total scattering cross sections for slow electrons with incident kinetic energies below 120 meV. Our results are in excellent agreement with available experimental data. We also propose a new value for the electron affinity of Fr, provide the scattering length for electronic collisions with Rb, Cs, and Fr, and discuss the nuclear charge dependence of relativistic effects in the resonance profiles. (c) 2000 The American Physical Society.
Long, Zhuqing; Jing, Bin; Yan, Huagang; Dong, Jianxin; Liu, Han; Mo, Xiao; Han, Ying; Li, Haiyun
2016-09-01
Mild cognitive impairment (MCI) represents a transitional state between normal aging and Alzheimer's disease (AD). Non-invasive diagnostic methods are desirable to identify MCI for early therapeutic interventions. In this study, we proposed a support vector machine (SVM)-based method to discriminate between MCI patients and normal controls (NCs) using multi-level characteristics of magnetic resonance imaging (MRI). This method adopted a radial basis function (RBF) as the kernel function, and a grid search method to optimize the two parameters of SVM. The calculated characteristics, i.e., the Hurst exponent (HE), amplitude of low-frequency fluctuations (ALFF), regional homogeneity (ReHo) and gray matter density (GMD), were adopted as the classification features. A leave-one-out cross-validation (LOOCV) was used to evaluate the classification performance of the method. Applying the proposed method to the experimental data from 29 MCI patients and 33 healthy subjects, we achieved a classification accuracy of up to 96.77%, with a sensitivity of 93.10% and a specificity of 100%, and the area under the curve (AUC) yielded up to 0.97. Furthermore, the most discriminative features for classification were found to predominantly involve default-mode regions, such as hippocampus (HIP), parahippocampal gyrus (PHG), posterior cingulate gyrus (PCG) and middle frontal gyrus (MFG), and subcortical regions such as lentiform nucleus (LN) and amygdala (AMYG). Therefore, our method is promising in distinguishing MCI patients from NCs and may be useful for the diagnosis of MCI. PMID:27343830
Beck, Eric V; Brozell, Scott R; Blaudeau, Jean-Philippe; Burggraf, Larry W; Pitzer, Russell M
2009-11-12
Multireference spin-orbit configuration interaction calculations were used to determine the accuracy of 60-, 68-, and 78-electron shape-consistent relativistic effective core potentials (RECPs) for uranium V and VI ground and low-lying excited states. Both 5f(n) and (5f6d)(n), (n = 1, 2) reference spaces were investigated using correlation-consistent double-zeta quality basis sets. Accuracy was assessed against gas-phase experimental spectra. The 68-electron RECP calculations yielded low relative and rms errors and predicted the empirical ordering of states most consistently. PMID:19888778
Park, G Barratt; Jiang, Jun; Field, Robert W
2016-04-14
The C̃ (1)B2 state of SO2 has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. The asymmetry in the potential energy surface is expressed as a staggering in the energy levels of the ν3(') progression. We have recently made the first observation of low-lying levels with odd quanta of v3('), which allows us-in the current work-to characterize the origins of the level staggering. Our work demonstrates the usefulness of low-lying vibrational level structure, where the character of the wavefunctions can be relatively easily understood, to extract information about dynamically important potential energy surface crossings that occur at much higher energy. The measured staggering pattern is consistent with a vibronic coupling model for the double-minimum, which involves direct coupling to the bound 2 (1)A1 state and indirect coupling with the repulsive 3 (1)A1 state. The degree of staggering in the ν3(') levels increases with quanta of bending excitation, which is consistent with the approach along the C̃ state potential energy surface to a conical intersection with the 2 (1)A1 surface at a bond angle of ∼145°. PMID:27083727
Park, G. Barratt; Jiang, Jun; Field, Robert W.
2016-04-14
Here the C1B2 state of SO2 has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. The asymmetry in the potential energy surface is expressed as a staggering in the energy levels of the v'3 progression. We have recently made the first observation of low-lying levels with odd quanta of v'3, which allows us--in the current work--to characterize the origins of the level staggering. Our work demonstrates the usefulness of low-lying vibrational level structure, where the character of the wavefunctions can be relatively easily understood, to extract information about dynamicallymore » important potential energy surface crossings that occur at much higher energy. The measured staggering pattern is consistent with a vibronic coupling model for the double-minimum, which involves direct coupling to the bound 2 1A1 state and indirect coupling with the repulsive 3 1A1 state. The degree of staggering in the v'3 levels increases with quanta of bending excitation, which is consistent with the approach along the C state potential energy surface to a conical intersection with the 2 1A1 surface at a bond angle of ~145°.« less
NASA Astrophysics Data System (ADS)
Park, G. Barratt; Jiang, Jun; Field, Robert W.
2016-04-01
The C ˜ 1B2 state of SO2 has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. The asymmetry in the potential energy surface is expressed as a staggering in the energy levels of the ν3' progression. We have recently made the first observation of low-lying levels with odd quanta of v3', which allows us—in the current work—to characterize the origins of the level staggering. Our work demonstrates the usefulness of low-lying vibrational level structure, where the character of the wavefunctions can be relatively easily understood, to extract information about dynamically important potential energy surface crossings that occur at much higher energy. The measured staggering pattern is consistent with a vibronic coupling model for the double-minimum, which involves direct coupling to the bound 2 1A1 state and indirect coupling with the repulsive 3 1A1 state. The degree of staggering in the ν3' levels increases with quanta of bending excitation, which is consistent with the approach along the C ˜ state potential energy surface to a conical intersection with the 2 1A1 surface at a bond angle of ˜145°.
Search for resonances in positron-atom systems
NASA Technical Reports Server (NTRS)
Bhatia, A. K.; Drachman, Richard J.
1990-01-01
No one likes to see a scattering cross section curve that is too smooth; it is much more interesting to find bumps and wiggles and most interesting if it is possible to understand their cause. Several types of resonances were clearly established in positron-containing systems: those lying just below a degenerate threshold (like 2s-2p in hydrogenic atoms or ions) and those representing Coulomb bound states in a rearranged channel (like Ps + H reversing positron +H(-)). Recently, two new sorts of resonances have been reported for which the resonant mechanism is not clear. The first is a very low lying resonance in the e-Ps system (obtained by an adiabatic expansion method), and the second is a similarly low lying two channel resonance in the positron -H system (obtained by a close-coupling technique.) These developments encouraged the examination of such systems using the standard methods of stabilization and complex rotation. Most of the results are negative; the low lying resonances in either system are verified. Some indication of new resonances in the e(+)-He(+) system is found; this may be caused by the attraction between Ps in the n=2 state and the He(++) nucleus.
Iuchi, Satoru Koga, Nobuaki
2014-01-14
With the aim of exploring excited state dynamics, a model electronic Hamiltonian for several low-lying d−d states of [Fe(bpy){sub 3}]{sup 2+} complex [S. Iuchi, J. Chem. Phys. 136, 064519 (2012)] is refined using density-functional theory calculations of singlet, triplet, and quintet states as benchmarks. Spin−orbit coupling elements are also evaluated within the framework of the model Hamiltonian. The accuracy of the developed model Hamiltonian is determined by examining potential energies and spin−orbit couplings at surface crossing regions between different spin states. Insights into the potential energy surfaces around surface crossing regions are also provided through molecular dynamics simulations. The results demonstrate that the constructed model Hamiltonian can be used for studies on the d−d excited state dynamics of [Fe(bpy){sub 3}]{sup 2+}.
Xantheas, Sotiris S.
2012-08-01
We rely on a hierarchy of methods to identify the low-lying isomers for the pentagonal dodecahedron (H2O)20 and the H3O+(H2O)20 clusters. Initial screening of isomers was performed with classical potentials [TIP4P, TTM2-F, TTM2.1-F for (H2O)20 and ASP for H3O+(H2O)20] and the networks obtained with those potentials were subsequently reoptimized at the DFT (B3LYP) and MP2 levels of theory. For the pentagonal dodecahedron (H2O)20 it was found that DFT (B3LYP) and MP2 produced the same global minimum. However, this was not the case for the H3O+(H2O)20 cluster, for which MP2 produced a different network for the global minimum when compared to DFT (B3LYP). All low-lying minima of H3O+(H2O)20 correspond to hydrogen bonding networks having 9 ''free'' OH bonds and the hydronium ion on the surface of the cluster. The fact that DFT (B3LYP) and MP2 produce different results and issues related to the use of a smaller basis set, explains the discrepancy between the current results and the structure previously suggested [Science 304, 1137 (2004)] for the global minimum of the H3O+(H2O)20 cluster. Additionally, the IR spectra of the MP2 global minimum are closer to the experimentally measured ones than the spectra of the previously suggested DFT global minimum. The latter exhibit additional bands in the most red-shifted region of the OH stretching vibrations (corresponding to the ''fingerprint'' of the underlying hydrogen bonding network), which are absent from both the experimental as well as the spectra of the new structure suggested for the global minimum of this cluster.
Low-lying electronic states of carotenoids.
DeCoster, B; Christensen, R L; Gebhard, R; Lugtenburg, J; Farhoosh, R; Frank, H A
1992-08-28
Four all-trans carotenoids, spheroidene, 3,4-dihydrospheroidene, 3,4,5,6-tetrahydrospheroidene, and 3,4,7,8-tetrahydrospheroidene, have been purified using HPLC techniques and analyzed using absorption, fluorescence and fluorescence excitation spectroscopy of room temperature solutions. This series of molecules, for which the extent of pi-electron conjugation decreases from 10 to seven carbon-carbon double bonds, exhibits a systematic crossover from S2----S0 (1(1)Bu----1(1)Ag) to S1----S0 (2(1)Ag----1(1)Ag) emission with decreasing chain length. Extrapolation of the S1----S0 transition energies indicates that the 2(1)Ag states of longer carotenoids have considerably lower energies than previously thought. The energies of the S1 states of spheroidenes and other long carotenoids are correlated with the S1 energies of their chlorophyll partners in antenna complexes of photosynthetic systems. Implications for energy transfer in photosynthetic antenna are discussed. PMID:1510992
Multiscale hierarchical support vector clustering
NASA Astrophysics Data System (ADS)
Hansen, Michael Saas; Holm, David Alberg; Sjöstrand, Karl; Ley, Carsten Dan; Rowland, Ian John; Larsen, Rasmus
2008-03-01
Clustering is the preferred choice of method in many applications, and support vector clustering (SVC) has proven efficient for clustering noisy and high-dimensional data sets. A method for multiscale support vector clustering is demonstrated, using the recently emerged method for fast calculation of the entire regularization path of the support vector domain description. The method is illustrated on artificially generated examples, and applied for detecting blood vessels from high resolution time series of magnetic resonance imaging data. The obtained results are robust while the need for parameter estimation is reduced, compared to support vector clustering.
Analysis of Three Body Resonances in the Complex Scaled Orthogonal Condition Model
Odsuren, M.; Katō, K.; Aikawa, M.
2014-06-15
Although the resonance structures of α+α+n have been studied experimentally and theoretically, it is still necessary to have more accurate and comprehensive understandings of the structure and decay of the low-lying excited states in {sup 9}Be. To perform calculations of an α+α+n system, we investigate five resonant states of α+α subsystem by utilizing different potential parameters and basis functions. In addition, two resonance states of α+n subsystem are computed.
Meier, R.; Boschitz, E.; Brinkmoeller, B.; Buehler, J.; Ritt, S.; Wessler, M. ); Konter, J.A.; Mango, S.; van den Brandt, B. ); Efimovykh, V.A.; Kovalev, A.I.; Prokofiev, A.N.; Polyakov, V.V. ); Chaumette, P.; Deregel, J.; Durand, G.; Fabre, J. ); Mach, R. ); Tacik, R. )
1994-01-01
The inclusive vector analyzing power [ital iT][sub 11] of [pi][sup +][r arrow][sup 7]Li elastic scattering and inelastic scattering to the 0.47 MeV excited state was measured at several angles for [ital T][sub [pi
NASA Astrophysics Data System (ADS)
Voss, C. I.; Gingerich, S. B.
2015-12-01
Low-lying oceanic islands host thin freshwater lenses subject to long-term aquifer salinization by seawater overwash. The lens is often the sole-source water supply for inhabitants. As maximum elevation for these islands is only a few meters above sea level, overwash can occur during high tides and storm surges. Sea level rise due to climate change will make overwash events even more common. The thin freshwater lenses, a few meters thick, are underlain by seawater, so pumping must be done carefully, often with horizontal skimming wells. Even a small amount of downward seawater infiltration from an overwash event can render the water supply non-potable. Where permeability is high, seawater infiltrates quickly, but seawater that infiltrates lower-permeability zones may remain for many months causing groundwater to remain non-potable, leaving residents without a reliable freshwater source. Initial post-overwash salinization is driven by the higher density of the invading saltwater, which sinks and mixes into the fresher water in potentially-complex patterns determined by: distribution of flooding and post-flood ponding, locations of permeable paths, and the inherently complex flow fields generated when fluid of higher density overlies lower-density fluid. The flow patterns cannot generally be measured or predicted in detail. This study develops basic understanding of overwash salinization processes impacting water supply on low-level islands, using a rare example of a monitored seawater overwash event that occurred in December 2008 at Roi-Namur Island in Kwajalein Atoll, Republic of the Marshall Islands, in which the salinity evolution of well water was measured. Due to typical lack of field data on such islands, a set of plausible alternative simulation-model descriptions of the hydrogeology and overwash event are created for analysis of the monitored salinization and recovery. Despite inability to know the 'true and complete' description of the event and the
The spectrum of scalar-meson nonets in the Resonance-Spectrum Expansion
Beveren, Eef van; Rupp, George
2008-08-31
We argue that the low-lying scalar-meson nonet makes part of a subset of a family of infinitely many scalar-meson nonets, which in turn makes part of a family of infinitely many quark-antiquark bound states and resonances. We outline the properties of this subset.
NASA Astrophysics Data System (ADS)
Taylor, David P.
2001-01-01
Vector addition is an important skill for introductory physics students to master. For years, I have used a fun example to introduce vector addition in my introductory physics classes based on one with which my high school physics teacher piqued my interest many years ago.
NASA Astrophysics Data System (ADS)
Xiao, Han; Wang, Dingbao; Hagen, Scott C.; Medeiros, Stephen C.; Hall, Carlton R.
2016-07-01
A three-dimensional variable-density groundwater flow and salinity transport model is implemented using the SEAWAT code to quantify the spatial variation of water-table depth and salinity of the surficial aquifer in Merritt Island and Cape Canaveral Island in east-central Florida (USA) under steady-state 2010 hydrologic and hydrogeologic conditions. The developed model is referred to as the `reference' model and calibrated against field-measured groundwater levels and a map of land use and land cover. Then, five prediction/projection models are developed based on modification of the boundary conditions of the calibrated `reference' model to quantify climate change impacts under various scenarios of sea-level rise and precipitation change projected to 2050. Model results indicate that west Merritt Island will encounter lowland inundation and saltwater intrusion due to its low elevation and flat topography, while climate change impacts on Cape Canaveral Island and east Merritt Island are not significant. The SEAWAT models developed for this study are useful and effective tools for water resources management, land use planning, and climate-change adaptation decision-making in these and other low-lying coastal alluvial plains and barrier island systems.
Baryon Spectroscopy and Resonances
Robert Edwards
2011-12-01
A short review of current efforts to determine the highly excited state spectrum of QCD, and in particular baryons, using lattice QCD techniques is presented. The determination of the highly excited spectrum of QCD is a major theoretical and experimental challenge. The experimental investigation of the excited baryon spectrum has been a long-standing element of the hadronic-physics program, an important component of which is the search for so-called 'missing resonances', baryonic states predicted by the quark model based on three constituent quarks but which have not yet been observed experimentally. Should such states not be found, it may indicate that the baryon spectrum can be modeled with fewer effective degrees of freedom, such as in quark-diquark models. In the past decade, there has been an extensive program to collect data on electromagnetic production of one and two mesons at Jefferson Lab, MIT-Bates, LEGS, MAMI, ELSA, and GRAAL. To analyze these data, and thereby refine our knowledge of the baryon spectrum, a variety of physics analysis models have been developed at Bonn, George Washington University, Jefferson Laboratory and Mainz. To provide a theoretical determination and interpretation of the spectrum, ab initio computations within lattice QCD have been used. Historically, the calculation of the masses of the lowest-lying states, for both baryons and mesons, has been a benchmark calculation of this discretized, finite-volume computational approach, where the aim is well-understood control over the various systematic errors that enter into a calculation; for a recent review. However, there is now increasing effort aimed at calculating the excited states of the theory, with several groups presenting investigations of the low-lying excited baryon spectrum, using a variety of discretizations, numbers of quark flavors, interpolating operators, and fitting methodologies. Some aspects of these calculations remain unresolved and are the subject of intense
Guilfoyle, Richard A.; Smith, Lloyd M.
1994-01-01
A vector comprising a filamentous phage sequence containing a first copy of filamentous phage gene X and other sequences necessary for the phage to propagate is disclosed. The vector also contains a second copy of filamentous phage gene X downstream from a promoter capable of promoting transcription in a bacterial host. In a preferred form of the present invention, the filamentous phage is M13 and the vector additionally includes a restriction endonuclease site located in such a manner as to substantially inactivate the second gene X when a DNA sequence is inserted into the restriction site.
Guilfoyle, R.A.; Smith, L.M.
1994-12-27
A vector comprising a filamentous phage sequence containing a first copy of filamentous phage gene X and other sequences necessary for the phage to propagate is disclosed. The vector also contains a second copy of filamentous phage gene X downstream from a promoter capable of promoting transcription in a bacterial host. In a preferred form of the present invention, the filamentous phage is M13 and the vector additionally includes a restriction endonuclease site located in such a manner as to substantially inactivate the second gene X when a DNA sequence is inserted into the restriction site. 2 figures.