Determination of the isotopic shift of the first resonance line in Cs(I) spectrum for the isotopes 131Cs, 132Cs,and 136Cs

The isotope shifts of the resonance line $\text{λ = 8521}\text{A}\text{?}$ of ¹³¹Cs, ¹³²Cs, and ¹³⁶Cs with respect to ¹³³Cs were determined by a new scanning technique to be $\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{131}\text{Cs}\text{) = +1.70(40)}\text{mK}$, $\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{132}\text{Cs}\text{) = ?0.95(80)}\text{mK}$, $\text{v}\text{?}\text{(}{}^{136}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{) = ?4.0(3.0)}\text{mK}$. In accordance with results from other Cs isotopes and neighbouring elements they show the change 〈δr²〉 in the second radial moment of the nuclear charge distribution to be a factor of 5 to 10 smaller than expected from the model of uniform charge distribution. Integral isotope shifts over the isotopic chains of Xe, Cs, and Ba were analyzed in terms of collective models. Assuming an isotopic shift discrepancy of 0.5 for the nuclear volume shift it was possible to derive deformation parameters $\text{〈β}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ in quantitative agreement with those from B(E2) measurements.     

Electronic structure and metal-nonmetal transition in liquid Cs−Sb and Cs−I systems

The electronic structures of liquid Cs–Sb and liquid Cs–I systems have been calculated using the self-consistent semirelativistic APW method within the superlattive model. We have investigated the nature of chemical bonding in connection with the composition dependent metal-nonmetal transition in these systems. It is found that Cs–Sb system is principally ionic as well as Cs–I system, but appreciable admixture of the metallic bonding is observed; this explains the different behavior between the two systems in their composition-induced metal-nonmetal transitions.     

Phase transitions and127I,133Cs quadrupole couplings in polycrystalline Cesium metaperiodate

The¹²⁷I and¹³³Cs NMR spectra of polycrystalline CsIO₄, a material of potential interest for transformation of laser irradiation, have been measured in the temperature range 170–440 K and the line shape has been analyzed taking into account first and second order quadrupole interactions and chemical shift anisotropy. Quadrupole coupling constants and asymmetry parameters have been determined as a function of temperature.¹²⁷I and¹³³Cs data consistently show two phase transitions in the ranges 243–300 K and 420–440 K with a temperature hysteresis for the first transition and a range for coexistence of two phases. The time evolution of the NMR signal suggests the existence of piezomagnetism, which was believed to exist only in crystals with a magnetic structure.     

Isotope shift in the resonance lines of the arc spectrum of133Cs,135Cs,and137Cs

Reactor Cs and mixtures of electromagnetically enriched Cs were used to investigate the isotopic shift of the two resonance lines. By a digital evaluation method anomalies in the isotope shift were found.     

Precise numerical results for limit cycles in the quantum three-body problem

The study of the three-body problem with short-range attractive two-body forces has a rich history going back to the 1930s. Recent applications of effective field theory methods to atomic and nuclear physics have produced a much improved understanding of this problem, and we elucidate some of the issues using renormalization group ideas applied to precise nonperturbative calculations. These calculations provide 11-12 digits of precision for the binding energies in the infinite cutoff limit. The method starts with this limit as an approximation to an effective theory and allows cutoff dependence to be systematically computed as an expansion in powers of inverse cutoffs and logarithms of the cutoff. Renormalization of three-body bound states requires a short range three-body interaction, with a coupling that is governed by a precisely mapped limit cycle of the renormalization group. Additional three-body irrelevant interactions must be determined to control subleading dependence on the cutoff and this control is essential for an effective field theory since the continuum limit is not likely to match physical systems (e.g., few-nucleon bound and scattering states at low energy). Leading order calculations precise to 11-12 digits allow clear identification of subleading corrections, but these corrections have not been computed.     

强磁场下Cs原子超精细塞曼能级上的光泵浦研究

强磁场中的Ｃｓ原子有较大的超精细塞曼分裂，实验用频率可调谐的窄线宽半导体激光调谐到各超精细塞曼能级上进行光泵浦，利用稳态吸收谱方法研究了原子的光泵浦。表明基态超精细相互作用的碰撞修正项导致的驰豫跃迁是谱形状和电子自旋极化新特征的根缘。同时提出了强场下极化度的一种测量方法。     

Riemann-Cartan-Weyl quantum geometry,I: Laplacians and supersymmetric systems

In this first article of a series dealing with the geometry of quantum mechanics, we introduce the Riemann-Cartan-Weyl (RCW) geometries of quantum mechanics for spin-0 systems as well as for systems of nonzero spin. The central structure is given by a family of Laplacian (or D'Alembertian) operators on forms of arbitrary degree associated to the RCW geometries. We show that they are conformally equivalent with the Laplacian operators introduced by Witten in topological quantum field theories. We show that the Laplacian RCW operators yield a supersymmetric system, in the sense of Witten, and study the relation between the RCW geometries and the symplectic structure of loop space. The RCW family of Laplacians are the infinitesimal generators of diffusion processes on nondegenerate space-times of systems of arbitrary spin.     

Uniform acceleration and the quantum field theory vacuum,I

Free massless scalar and Dirac fields are quantized in two-dimensional Minkowski space in a representation in which the energy operator for a uniformly accelerating observer is diagonalized. The usual vacuum, and many other pure states, appear to be thermally excited in this representation. The crucial role ot PCT symmetry, as regards the general validity of this conclusion, is illustrated.     

Energy spectra of delayed neutrons from separated fission products: (III). The precursors 88Br, 90Br, 138I, 140I, 142(Xe+Cs) and 144Cs

Energy spectra of delayed neutrons from the mass-separated fission products ^{88. 90}Br, ^{138, 14}I, ¹⁴²(Xe+Cs) and ¹⁴⁴Cs have been measured. Average level spacings, neutron envelopes and P_n values were calculated and compared with the experimental data. The neutron envelopes are well reproduced for all precursors except ⁹⁰Br and ¹⁴⁰I. For the latter the neutron window predicted by various mass formulae is too wide and a considerable reduction was found necessary to bring calculated envelopes in agreement with the experimental distributions.     

The local structure of Cs(I) and Cs(II) in a Cs2ZnCl4 single crystal studied by nuclear magnetic resonance

The rotation patterns of the ¹³³Cs (I=7/2) nuclear magnetic resonance (NMR) in a Cs₂ZnCl₄ single crystal grown by using the slow evaporation method were measured in two mutually perpendicular crystal planes. Two different groups of Cs resonances were recorded; this result points to the existence of two types of crystallographically inequivalent Cs(I) and Cs(II). The angular dependences of the NMR spectra led to different values for the quadrupole coupling constants and asymmetry parameters: e²qQ/h=148 kHz and η=0.11 for the Cs(I) ion, and e²qQ/h=274 kHz and η=0.66 for the Cs(II) ion. The EFG tensors of Cs(I) and Cs(II) are asymmetric, and the orientations of the principal axes of the EFG tensors do not coincide. Only, the principal Y-axes of the EFG tensors coincide for the Cs(I) and Cs(II) sites. The Cs(I) ion is surrounded by 11 chlorine ions, making it rather free and high in symmetry. The Cs(II) ion has only nine neighbors and seems to be more tight than the Cs(I) ion.     

Representation of fuzzy quantum posets of types I,II

Let (,M) be a fuzzy quantum poset of type I, II, or FQP of type I, II for short. For Boolean representations of fuzzy quantum spaces, by a representation of (,M) we mean a quantum logic (i.e., an orthocomplemented-orthocomplete orthomodular poset with a homomorphismh: such that for any states onM and any observable ¯X on there is a state ¯s on and observableX onM such that the following diagram commutes [where () is a Borel-algebra of the real line ]: We prove that a representation of FQP of type I always exists and a representation of FQP of type II exists in some cases.     

Autoionization in the evolution process of dense Rb Rydberg atoms in nP states

The autoionization mechanisms of dense nP_3/2 (n = 20–97) Rydberg gases of ⁸⁷Rb atoms in the spontaneous evolution were investigated for the first time. By observing the characteristic time of the electrons generated through autoionization process, the dependence of autoionization mechanisms (black-body radiation, electron–Rydberg collision, and Penning ionization) on the principal quantum number n of initial nP states was demonstrated. The dependence on the number n in nP Rydberg atoms is similar to those in nD Rydberg atoms.     

Ferroelectric phase transition in Cs3Bi2I9

Single crystals of Cs₃Bi₂I₉ have been grown. Polarized-optical, dielectric, and calorimetric studies have been performed, along with measurements of birefringence, and the coefficients of elasticity c ₄₄, and linear expansion a over a wide temperature range. It is found that an intrinsic (pseudo-intrinsic) second-order phase transition to the ferroelastic phase takes place at T ₀=220.0±0.6 K accompanied by a change of the crystal symmetry from 6/mmc to 2/m. The transition parameter depends linearly on the shear strain x ₅ and varies with temperature according to a power law with exponent β=0.5. Zh. éksp. Teor. Fiz. 39, 1850–1852 (October 1997)     

Dynamics of uniform quantum gases, I: Density and current correlations

A unified approach valid for any wavenumber q, frequency ω, and temperature T is presented for uniform ideal quantum gases allowing for a comprehensive study of number density and particle-current density response functions. Exact analytical expressions are obtained for spectral functions in terms of polylogarithms. Also, particle-number and particle-current static susceptibilities are presented which, for fugacity less than unity, additionally involve Kummer functions. The q- and T-dependent transverse-current static susceptibility is used to show explicitly that current correlations are of long range in a Bose-condensed uniform ideal gas but for bosons at T>T_c and for Fermi and Boltzmann gases at all temperatures these correlations are of short range. Contact repulsive interactions for systems of neutral quantum particles are considered within the random phase approximation. The expressions for particle-number and transverse-current susceptibilities are utilized to discuss the existence or nonexistence of superfluidity in the systems under consideration.