存在偶极间相互作用的两能级原子的消相干

两个两能级原子置于外部环境(热库)中,当计及原子偶极间的相互作用时,通过研究两个原子约化密度矩阵,分析原子状态消相干规律。     

The study of interaction potentials and differential cross sections for collisions between He atoms and hydrogen halide molecules

In this paper, we present the uniform interaction potentials for helium atoms and halogen hydride molecules (HF, HCl and HBr). The differential cross sections are calculated using the above interaction potentials for the He－HF, HCl and HBr systems, respectively, and the results of the calculations are found to be in agreement with the existing theoretical results and experimental data.     

Folding potential for nonlocal pair interaction

A general expression is obtained in the coordinate representation for the folding potential describing the interaction of an incoming structureless particle with the centre of mass of a composite nucleus in the case of nonlocal pair interactions. This expression is derived using the Fourier transform of the folding potential in the momentum representation, written as a sum of triangle Feynman diagrams. Two vertices of such a diagram describe the virtual decay of the nucleus into nucleons and the inverse synthesis process. The third vertex is the Fourier component of the pair potential of interaction of the incoming particle with a nucleon belonging to this nucleus. A similar approach was used to obtain the expression for the double-folding potential describing the interaction of two composite objects (nuclei).     

Collisions of alkali K and Rb atoms in ground state: Modification of interaction potentials

The interaction of alkali K and Rb atoms that reside in the ground state is considered in the range of collision energies E = 10⁻⁴ to 10⁻² au. The singlet (X ¹Σ⁺) and triplet (a ³Σ⁺) interaction potentials available in the literature are analyzed and modified. For the KRb dimer in the range of interatomic distances 15–21a ₀, we chose analytical representations of the singlet and triplet potentials that more accurately describe the interaction of alkali Rb and K atoms in the ground state. Complex cross sections of the spin exchange are calculated for the first time that permit one to calculate the processes of polarization transfer and relaxation times, as well as shifts in the magnetic resonance frequencies caused by K-Rb spin exchange collisions.     

Evaporation of atoms from femtosecond laser-heated gallium arsenide

The surface temperature of a GaAs crystal irradiated with 150 fs laser pulses is determined from the Maxwell velocity distribution of the evaporated atoms. The crystal is strongly superheated, and melting is observed to occur at a temperature 600–1000 K above the equilibrium melting point.     

Radiative decay of a pair of atoms

In view of earlier incomplete treatments, the development in time of the radiative decay of a pair of two identical, neutral and fixed two-level atoms, sharing initially a single excitation, is reexamined.     

Effective potentials of lithium and sodium atoms

The effective potentials of lithium and sodium atoms are reconstructed using the Bohr-Sommerfeld quantization conditions. It is shown that the effective potentials can be expressed in analytical form. A comparison with the Seitz and Prokofjew potentials is made.     

Calculation of pair potentials for systems with filled shells

The possibility of calculating homoatomic and heteroatomic pair potentials for systems with filled shells by a density-functional method in which the parameters of the Hartree-Fock electron density of the isolated atoms are found by the Ritz variational method is discussed.Kabardino-Balkarian State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, No. 6, pp. 3–8, June, 1994.     

Description of the geometry of crystals with a hexagonal close-packed structure based on pair interaction potentials

The pair force interaction potential that allows one to describe a deviation from spherical symmetry, which is typical for hexagonal close-packed structures, is constructed using the ??spherically symmetric?? Mie potential that depends only on the interatomic distance. The parameters of the considered potential, which ensure the stability of hexagonal close-packed lattices, are obtained for a wide range of metals, namely, beryllium, gadolinium, hafnium, holmium, dysprosium, yttrium, cobalt, lutetium, magnesium, osmium, rhenium, ruthenium, scandium, thallium, terbium, technetium, titanium, thulium, cerium, zirconium, and erbium. It is shown that for this pair interaction potential the hexagonal close-packed structure is energetically more favorable than the face-centered cubic structure. The proposed potential can be used to perform computational experiments and analytical investigations.     

Spatial pair correlations of atoms in molecular dissociation

We perform first-principles quantum simulations of dissociation of trapped, spatially inhomogeneous Bose-Einstein condensates of molecular dimers. Specifically, we study spatial pair correlations of atoms produced in dissociation after time of flight. We find that the observable correlations may significantly degrade in systems with spatial inhomogeneity compared to the predictions of idealized uniform models. We show how binning of the signal can enhance the detectable correlations and lead to the violation of the classical Cauchy-Schwartz inequality and relative number squeezing.     

Lambda-nucleon interaction potentials

Two-body S-wave, spin dependent, central Λ-N interaction potentials of the form first given by Ram and Downs are constructed to fit the zero energy scattering lengths a_s = −2.25 fm, a_t = −2.08 fm of Herndon and Tang. When assumed to be effective in even-parity states with full strength and in odd-parity states with zero strength, these potentials fit the Λ-p scattering cross section data very well. The binding energy D of the Λ-particle in nuclear matter using these potentials is calculated by the method of independent pair approximation. The potentials that best fit the scattering data give values for D which are only 3–4 MeV lower than that obtained previously with a potential of Hemdon and Tang. It is concluded that the three-body ΛNN forces may be quite important in the calculations of D.     

Diffusion and solubility of electrically active iron atoms in gallium arsenide

Iron diffusion in GaAs at arsenic pressure 1 atm is studied. The temperature dependences of the diffusion coefficient and solubility of electrically active iron atoms in GaAs are determined. The dependences can be described by the Arrhenius equations with the following parameters: D ₀ = 1.61 cm²/s and E = (2.16 ± 0.47) eV (for diffusion) and N _S ⁰ = 4.62 ⋅ 10²³ cm⁻³ and E _S = (1.61 ± 0.16) eV (for solubility). The results obtained are compared with the earlier published data. The concentration of electrically active iron atoms is shown to be about 2 times lower than the total iron concentration in GaAs. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 39–41, November, 2008.     

Relation between chemical and ionization potentials in atoms

The chemical potential μ in an atom is calculated by going to infinite distance from the nucleus. Then the kinetic energy contribution to μ is shown to be - I, with I the ionization potential. The potential energy per particle from correlation is obtained for the additional contribution from a local density approximation.     

Liquid metal pair potentials from structure data

In linear screening theory, the zeroth order result is the equality of the potential of mean force and the pair potential. The Kirkwood superposition approximation holds to the same order.The next order yields an equation for the pair potential identical with the first order iteration of Johnson and March from the Born-Green equation.     

Non-Abelian gauge potentials for ultracold atoms with degenerate dark states

We show that the adiabatic motion of ultracold, multilevel atoms in spatially varying laser fields can give rise to effective non-Abelian gauge fields if degenerate adiabatic eigenstates of the atom-laser interaction exist. A pair of such degenerate dark states emerges, e.g., if laser fields couple three internal states of an atom to a fourth common one under pairwise two-photon-resonance conditions. For this so-called tripod scheme we derive general conditions for truly non-Abelian gauge potentials and discuss special examples. In particular we show that using orthogonal laser beams with orbital angular momentum an effective magnetic field can be generated that has a monopole component.