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AbstractAbstract

[en] The theory of level splitting of certain vibration-rotation states (including the ground state) in spherical-top molecules is developed within the framework of the standard Racah-Wigner tensor algebra, thus demonstrating the direct applicability of these general techniques without making the usual modifications associated with the anomalous commutation relations of the body-fixed angular momentum components. The eigenvalue spectrum of the octahedrally invariant fourth-rank tensor operator is examined in detail, and the unexpected periodic symmetry and asymptotic degeneracy features of the spectrum are described

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Physical Review. A; v. 15(4); p. 1363-1381

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[en] Nuclear spectroscopy experiments provide critical evidence for the identification of mixed symmetry states. Examples of these states in vibrational nuclei are considered with some reference to rotational and γ-unstable nuclei

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Meyer, R.A.; Paar, V; p. 338-349; ISBN 9971-50-141-4; ; 1986; p. 338-349; World Scientific Pub. Co; Teaneck, NJ (USA); International conference on nuclear structure, reactions, and symmetries; Dubrovnik (Yugoslavia); 5-14 Jun 1986

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AbstractAbstract

[en] A model of the time evolution of two interacting Rydberg manifolds of energy levels subject to a linearly ramped electric field is solved exactly in the Landau-Zener (LZ) approximation. Each manifold close-quote s levels are treated as linear in time, parallel, equally spaced, and infinite in number. Their pairwise interactions produce a regular two-dimensional grid of isolated anticrossings. The time development of an initially populated state is then governed by two-level LZ transitions at avoided crossings and adiabatic evolution between them, parametrized by the LZ transition probability D and a dynamical phase unit var-phi. The resulting probability distributions of levels are given analytically in the form of recursion relations, generating functions, integral representations involving D and var-phi, and in certain limits by Bessel or Whittaker functions. Level populations are mapped out versus location on the grid for a range of cases. Interference effects lead to two principal types of probability distributions: a braiding adiabatic pattern with revivals for small D and a diabatic pattern for D→1 in which only certain levels parallel to the initial one are appreciably populated. The sensitivity of the coherent evolution to var-phi is discussed, along with the relation of this model to others and to selective-field ionization. copyright 1997 The American Physical Society

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AbstractAbstract

[en] In a model of interacting Rydberg manifolds, two sets of parallel energy levels, E

_{m}(t) = pt - mε and E_{m'}(t)=p't + m'ε' (m,m' = 0, ±1,...;p' ≠ p), are linearly shifted by an electric field F(t) = Ft. Atomic core coupling V occurs only at the point of each pair of levels intersection, with a Landau-Zener diabatic transition probability D = d^{2}= e^{-2}πV^{2}/|p-p'|. Adiabatic phases depend on the unit of action, var-phi = contour-integral dt E(t) = εε'/|p-p'|. The amplitudes for approaching the intersection of levels m and m' from an initial m = 0 at m' = 0 are found from recursion relations, similar to an earlier model but including paths' interference via operators ξ and η, where ηξ = ξηe^{ivar-phi}. Coefficients of ordered power ξ^{m}η^{m}^{'}in the generating functions 1 + η[1 + d(η-ξ) - ξη]^{-1}(ξ - d) and αξ[1 + d(η - ξ) - ηξ]^{-1}yield the amplitudes for m- and m'-levels. Another exact form for the amplitudes is obtained from integral representations. In the adiabatic limit (d → 0) the one for m-levels reduces to J_{m-m'}(2d sin [1/2m'var-phi]/sin[1/2 var-phi]); in the diabatic limit (d → 1) it reduces to a Whittaker function. These results help explain overall patterns in the population distributions during coherent evolution under field rampingPrimary Subject

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27. annual meeting of the Division of Atomic, Molecular and Optical Physics (DAMOP) of the American Physical Society (APS); Ann Arbor, MI (United States); 15-18 May 1996; CONF-9605105--

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AbstractAbstract

[en] The frontier areas of nuclear spectroscopy; namely extensions to I) larger angular momentum, II) higher temperature, III) the amalgamation of aligned and 'vibrational' configurations at intermediate spins, and IV) new regions of deformed nuclei, are discussed. Recent experimental results are highlighted, and the physics which remains to be addressed in each area is discussed. (orig.)

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International workshop on collective states in nuclei; Suzhou (China); 8-18 Sep 1983; With 65 refs.; CODEN: NUPAB.

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Nuclear Physics. A; ISSN 0375-9474; ; v. 421 p. 313-338

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AbstractAbstract

[en] Excitation spectra of CdNe, CdAr and ZnAr van der Waals molecules studied in a free-jet expansion beam crossed with a pulsed dye-laser beam. The molecules were produced as Cd (or Zn) atoms seeded in Ne on Ar were expanded through a nozzle, and the excitation spectra were recorded by scanning the second harmonic output of the dye laser in the immediate vicinity of the Cd(5

^{1}P_{1}left-arrow 5^{1}S_{0}) or Zn(4^{1}P_{1}left-arrow 4^{1}S_{0}) atomic transitions in the range 2288-2290.5 Angstrom for CdNe, 2288-2305.5 Angstrom for CdAr, and 2137-2160 Angstrom for ZnAr. Analysis of the vibrational structures of the spectra yielded the molecular constants ω_{e}, ω_{e}χ_{e}, and D_{e}for the D1 states. Computer modelling of the spectra produced the relative equilibrium internuclear separations. We found a linear dependence of the dissociation energy on the polarizability of the rare-gas (RG) partners for all the above molecules. This, in turn, leads to some interesting predictions of the molecular constants for molecules not yet investigated (e.g. CdHe, ZnRG, HgHe, NaHe, etc.). We also suggest empirical values for the polarizabilities of Cd, Zn and Hg atoms in the ground and the first excited (^{3}p_{1}) states, derived from spectroscopic dataPrimary Subject

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1993 American Physical Society annual meeting on atomic, molecular, and topical physics; Reno, NV (United States); 16-19 May 1993; CONF-9305421--

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AbstractAbstract

[en] The expansions in terms of angular momentum I or angular frequency ω that describe the energies of the levels in the ground-state rotational bands with Ksup(π)=O

^{+}are generally not equivalent unless n_{1}=n_{2}=1 or infinity. A method is proposed to characterise this non-equivalency quantitatively. It was found that in some nuclei, like^{248}Cm and^{166}Er, the I(I + 1) expansion is better than the ω^{2}expansion, whereas in the majority of nuclei the ω^{2}expansion is better. The data demonstrate that the rates of convergence of the I(I + 1) and ω^{2}expansions for Esub(rot) depend on the individual properties of the nuclei. (author)Primary Subject

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Journal of Physics. G, Nuclear Physics; ISSN 0305-4616; ; v. 9(9); p. 1025-1032

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Leiden, S.H.

State Univ. of New York, Binghamton (USA)

State Univ. of New York, Binghamton (USA)

AbstractAbstract

[en] A modified rotational energy band structure for an axially symmetric deformed even-even nucleus is derived under the assumption that all nucleons outside a filled nuclear core have angular momentum j, with j >> 1. An expansion derived by Belyaev and Zelevinski is used to express important band operators explicity as a function of the total angular momentum of the nucleus. These operators are then inserted into an equation of motion describing nuclear rotation, and band transition energies W

^{2}are calculated for nuclear transitions within a single rotational band. It is found that one adjustable parameter will suffice to specify the band structure given by W^{2}, and this band structure may be made to have energy level spacings lying between pure rotation and pure vibrationPrimary Subject

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1981; 185 p; L; 80-28,478; Thesis (Ph. D.).

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Report

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Thesis/Dissertation

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No abstract available

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Johannes Kepler Univ., Linz (Austria); 40 p; 1985; p. 15; European Conference on Computer Algebra; Linz (Austria); 1-3 Apr 1985; Published in summary form only.

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[en] We propose a method for including the fractional occupancy of electronic energy levels within a tight-binding density-matrix formalism. This method is based on successful techniques used in first-principles methods. Molecular-dynamics test simulations show that the density-matrix technique accurately reproduces the physics of a direct-diagonalization simulation using Fermi-Dirac occupancy. copyright 1996 The American Physical Society

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