SHAPE ISOMERISM OF SODIUM CLUSTERS WITH QUADRUPOLE, OCTUPOLE, AND HEXADECAPOLE DEFORMATIONS IN THE STRUCTURE-AVERAGED JELLIUM MODEL

1996 ◽  
Vol 03 (01) ◽  
pp. 229-233 ◽  
Author(s):  
TH. HIRSCHMANN ◽  
M. BRACK ◽  
B. MONTAG ◽  
P.-G. REINHARD ◽  
J. MEYER
Keyword(s):  
Cross Sections ◽  
Local Density ◽  
Deformation Energy ◽  
Jellium Model ◽  
Dipole Resonance ◽  
Sodium Clusters ◽  
Left Right Asymmetry ◽  
Singly Charged ◽  
Energy Surfaces ◽  
Good Agreement

Multidimensional deformation energy surfaces of singly charged sodium clusters with 8≤ Z ≤50 valence electrons have been calculated including quadrupole, octupole, and hexadecapole shapes for the ionic background. We solve the Kohn-Sham equations in the local-density approximation with preserved axial symmetry on a two-dimensional lattice. In addition to the diffusivity of the jellium surface, the structure-averaged jellium model (SAJM) which yields the empirical bulk properties and surface tension of sodium is successfully applied to deformed systems. Discussing the systematics of shape transitions, we find good agreement with recent experimental dipole resonance splittings found in the photoabsorption cross sections and confirm the oblate shape of the first neighboring clusters above the closed 2p shell ( Z =40) provided that left-right asymmetry is enabled.

scholarly journals On the isotopic fingerprint exerted on carbonyl sulfide by the stratosphere

2012 ◽  
Vol 12 (9) ◽  
pp. 25329-25353 ◽  
Author(s):  
J. A. Schmidt ◽  
S. Hattori ◽  
N. Yoshida ◽  
S. Nanbu ◽  
M. S. Johnson ◽  
...  
Keyword(s):  
Cross Sections ◽  
Potential Energy Surfaces ◽  
Carbonyl Sulfide ◽  
Isotopic Fractionation ◽  
Data Sets ◽  
Mechanical Formalism ◽  
Model Study ◽  
Quantum Mechanical Formalism ◽  
Energy Surfaces ◽  
Good Agreement

Abstract. The isotopic fractionation in OCS photolysis is studied theoretically from first principles. UV absorption cross sections for OCS, OC33S, OC34S, OC36S and O13CS are calculated using the time-depedent quantum mechanical formalism and recent potential energy surfaces for the lowest four singlet and lowest four triplet electronic states. The calculated isotopic fractionations as a function of wavelength are in good agreement with recent measurements by Hattori et al. (2011) and indicate that photolysis leads to only a small enrichment of 34S in the remaining pool of OCS. A simple stratospheric model is constructed taking into account the main stratospheric sink reactions of OCS and it is found that stratospheric removal overall slightly favors light OCS in constrast to the findings of Leung et al. (2002). These results show, based on isotopic considerations, that OCS is an acceptable source of background stratosperic sulfate aerosol in agreement with a recent model study of Brühl et al. (2012). The 13C isotopic fractionation due to photolysis of OCS is significant and will leave a strong signal in the pool of remaining OCS making it a candidate for tracing using the ACE-FTS and MIPAS data sets.

scholarly journals New H2O–H2O collisional rate coefficients for cometary applications

2020 ◽  
Vol 498 (4) ◽  
pp. 5489-5497 ◽  
Author(s):  
C Boursier ◽  
B Mandal ◽  
D Babikov ◽  
M L Dubernet
Keyword(s):  
Cross Sections ◽  
Potential Energy Surfaces ◽  
Rate Coefficients ◽  
Molecular Systems ◽  
Large Sets ◽  
Alternative Approach ◽  
Collisional Rate Coefficients ◽  
Energy Surfaces ◽  
Good Agreement

ABSTRACT We re-introduce a semiclassical methodology based on theories developed for the determination of broadening coefficients. We show that this simple and extremely fast methodology provides results that are in good agreement with results obtained using the more sophisticate MQCT approach. This semiclassical methodology could be an alternative approach which allows to provide large sets of collisional data for very complex molecular systems. It saves time both on the determination of potential energy surfaces and on the collisional dynamical calculations. In addition, this paper provides more complete sets of rotational de-excitation cross-sections and rate coefficients of H2O perturbed by a thermal average of water molecules. Those data can be used in the radiative transfer modelling of cometary atmospheres.

Study of giant dipole resonances for neodymium isotopes with an exciton model

2020 ◽  
Vol 29 (10) ◽  
pp. 2050084
Author(s):  
Nabeel F. Lattoofi ◽  
Ali A. Alzubadi
Keyword(s):  
Cross Sections ◽  
Small Deformation ◽  
Neutron Number ◽  
Nd Isotope ◽  
Neodymium Isotopes ◽  
Dipole Resonance ◽  
Deformation Parameters ◽  
Empire Code ◽  
Fitting Parameters ◽  
Good Agreement

The partial photonuclear [Formula: see text], pn) and [Formula: see text] and the total photonuclear cross-sections (the giant dipole resonance (GDR)) have been investigated theoretically for neodymium isotopes, namely [Formula: see text]Nd, using framework of the EMPIRE 3.2.2 code. The energy, width and cross-section parameters of the GDR used in our calculations have been investigated in this paper depending on the deformation parameters of nuclei. The calculated results have been compared with the experimental data and with those calculated using Lorentzian fitting parameters. Our calculations show a good agreement for all isotopes under study and give better results than the results calculated with Lorentzian parameters. Furthermore, the neutron number dependence of the total and partial photonuclear cross-sections has also been discussed. The results appear that the EMPIRE code used is a perfect tool for reproducing the splitting in the GDR for deformed [Formula: see text]Nd isotope in two distinct dipole modes which are perfectly consistent with the experimental results. It has also been shown that the present parameters are suitable parameters for reproducing the GDR for spherical, or nearly spherical, and the deformed ([Formula: see text]Nd) neodymium isotopes. The parameters have been indicating the small deformation in [Formula: see text]Nd, which cannot be shown by the Lorentzian fitting parameters.

POTENTIAL-ENERGY SURFACES OF SODIUM CLUSTERS WITH QUADRUPOLE, HEXADECAPOLE, AND TRIAXIAL DEFORMATIONS

1996 ◽  
Vol 03 (01) ◽  
pp. 25-29 ◽  
Author(s):  
S.M. REIMANN ◽  
S. FRAUENDORF
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Correction Method ◽  
Model Potential ◽  
Shell Correction ◽  
Jellium Model ◽  
Sodium Clusters ◽  
Self Consistent ◽  
Particle Spectra ◽  
Energy Surfaces

Combining a modified Nilsson-Clemenger model with the shell-correction method, the potential-energy surfaces of sodium clusters with sizes of up to N = 200 atoms are calculated, including nonaxial deformations. For spherical clusters, the model potential is fitted to the single-particle spectra obtained from microscopically self-consistent Kohn-Sham calculations using the jellium model and the localdensity approximation. Employing the Strutinsky shell-correction method, the surface energy of the jellium model is renormalized to its experimental value. The ground-state shapes are determined by simultaneous minimization of the deformation energies for quadrupole, hexadecapole, and triaxial cluster deformations.

scholarly journals Determination of the Harmonic Oscillator Energy Level Spacing for Atomic Clusters

2019 ◽  
Vol 7 ◽  
pp. 63
Author(s):  
M. E. Grypeos ◽  
B. A. Kotsos
Keyword(s):  
Energy Level ◽  
Harmonic Oscillator ◽  
Particle Number ◽  
Model Potential ◽  
Atomic Clusters ◽  
Level Spacing ◽  
Jellium Model ◽  
Sodium Clusters ◽  
Good Agreement

The harmonic oscillator energy level spacing Κω for atomic clusters as a function of the particle number Ν is expressed analytically in terms of the parameters of a Woods-Saxon (or Symmetrized Woods-Saxon) potential which approximates the effective spherical self-consistent jellium model potential. The expressions derived depend an the particular scheme adopted to approximate the potential by the harmonic oscillator one and on the assumed dependence of the potential radius R on N. It is also observed, considering the case of sodium clusters,that for large Ν the expressions of Ηω are in good agreement with the well known expression of Ηω in terms of the Wigner-Seitz radius.

scholarly journals Parametrization of the effective potential in sodium clusters

2020 ◽  
Vol 4 ◽  
pp. 75
Author(s):  
B. A. Kotsos ◽  
M. E. Grypeos
Keyword(s):  
Particle Number ◽  
Local Density ◽  
Density Approximation ◽  
Jellium Model ◽  
Radius Parameter ◽  
Sodium Clusters ◽  
Fitting Procedures ◽  
Potential Parameters ◽  
Neutral Sodium ◽  
Wine Bottle

The effective radial electronic potentials for neutral sodium clus­ters determined by the local density approximation and the jellium model are parametrized by means οf (symmetrized) Woods-Saxon and "Wine-Bottle" symmetrized Woods-Saxon potentials. The potential parameters are deter­ mined by various least-squares fitting procedures. Particular attention is paid to the dependence of the radius parameter R on the particle number Ν and it is realized that for relatively smaller values of N, complex expressions of R as a function of N, are more appropriate than the standard one R = r_0N^{1/3}. It is also found that improved results in these cases are obtained with an expression, of the form R = r_0N^{1/3} + 6, which is still very simple.

scholarly journals Particle Number Dependence of Size and Energy Quantities in Sodium Clusters

2020 ◽  
Vol 5 ◽  
pp. 57
Author(s):  
B. A. Kotsos ◽  
M. E. Grypeos
Keyword(s):  
Particle Number ◽  
Local Density ◽  
Average Energy ◽  
Level Spacing ◽  
Jellium Model ◽  
Sodium Clusters ◽  
Fitting Procedures ◽  
Potential Parameters ◽  
Neutral Sodium ◽  
Wine Bottle

The effective radial electronic potentials for neutral sodium clusters, which were determined by Ekardt on the basis of the local density approximation and the jellium model, are parametrized by means of the (symmetrized) Woods-Saxon and "Wine-Bottle" symmetrized Woods-Saxon potentials with the aim of investigating the dependence of size and energy quantities on the cluster particle number. The potential parameters are determined by vari­ous least-squares fitting procedures. It is found that for the radius R of the above potentials, complex expressions are more appropriate than the stan­dard one R = r0N^{1/3} for relatively small values of N. Furthermore, N-power expansions are derived for those complex expressions of R, as well as for the r.m.s. radius of the potential. It is also found that improved results in these cases are obtained with an expression of the form R = r0N^{1/3}+b, which is still very simple. There is also investigated the variation of energy quan­tities, such as the single particle energies of the 1s and 1p states, the level spacing |E1p-E1s| and the average energy level spacing, with respect to the particle number N. Expressions for the first three of these quantities with N-dependent terms of the form aN^{2/3} + βΝ^{-1} give good results.

Analysis of Reinforced Concrete Culvert considering Concrete Creep and Shrinkage

1996 ◽  
Vol 1541 (1) ◽  
pp. 120-126
Author(s):  
Charles J. Oswald
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Cross Sections ◽  
Soil Structure ◽  
Silty Clay ◽  
Soil Pressure ◽  
Concrete Creep ◽  
Long Span ◽  
Creep And Shrinkage ◽  
Good Agreement

Measurements made on a long span reinforced concrete arch culvert under 7.3 m (24 ft) of silty clay backfill were compared with results from finite-element analyses of the soil-structure system using the CANDE finite-element code. The culvert strains and deflections and the soil pressure on the culvert were measured during construction and during the following 2.5 years at three instrumented cross sections. The CANDE program was modified to account for the effects of concrete creep and shrinkage strains after it was noted that the measured postconstruction culvert deflection and strains increased significantly whereas the measured soil pressure on the culvert remained relatively constant. Good agreement was generally obtained between measured and calculated values of the culvert strain and deflection and the soil pressure during the entire monitoring period after the code was modified.

Disorientation of Cs(62P1/2) atoms, induced in collisions with noble gases

1976 ◽  
Vol 54 (7) ◽  
pp. 748-752 ◽  
Author(s):  
B. Niewitecka ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Noble Gas ◽  
Zero Magnetic Field ◽  
Zero Field ◽  
Buffer Gas ◽  
Resonance Fluorescence ◽  
Circularly Polarized ◽  
Low Field ◽  
Good Agreement ◽  
Gas Pressures

The disorientation of 62P1/2 cesium atoms, induced in collisions with noble gas atoms in their ground states, was systematically investigated by monitoring the depolarization of cesium resonance fluorescence in relation to noble gas pressures. The Cs atoms, contained together with a buffer gas in a fluorescence cell and located in zero magnetic field, were excited and oriented by irradiation with circularly polarized 8943 Å resonance radiation, and the resonance fluorescence, emitted in an approximately backward direction, was analyzed with respect to circular polarization. The experiments yielded the following disorientation cross sections which have been corrected for the effects of nuclear spin: Cs–He: 4.9 ± 0.7 Å2; Cs–Ne: 2.1 ± 0.3 Å2; Cs–Ar: 5.6 ± 0.8 Å2; Cs–Kr: 5.8 ± 0.9 Å2; Cs–Xe: 6.3 ± 0.9 Å2. The results are in good agreement with most of the available zero-field and low-field data.

ELECTRONIC STRUCTURE AND OPTICAL PROPERTIES OF CRYSTALLINE C60

1992 ◽  
Vol 06 (06) ◽  
pp. 309-321 ◽  
Author(s):  
W.Y. CHING ◽  
MING-ZHU HUANG ◽  
YONG-NIAN XU ◽  
FANQI GAN
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Optical Spectrum ◽  
Local Density ◽  
Low Dielectric Constant ◽  
Experimental Measurements ◽  
Absorption Bands ◽  
Low Dielectric ◽  
Good Agreement

The electronic structure and optical properties of crystalline C 60 and their pressure dependence have been studied by first-principles local density calculations. It is shown that fcc C 60 has a low dielectric constant and an optical spectrum rich in structures. The spectrum shows five disconnected absorption bands in the 1.4 to 7.0 eV region with sharp structures in each band that can be attributed to critical point transitions. This is a manifestation of the localized molecular structure coupled with long range crystalline order unique to the C 60 crystal. At a sufficient high pressure, the structures in the optical spectrum start to merge due to the merging of the bands. These results are in good agreement with some recent experimental measurements.

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