On the interaction of a hydrogen atom with a lithium metal surface

In this paper we adopt a molecular cluster approach to study the interaction of a hydrogen atom with a (100) surface of solid lithium metal. In this study, the spin-unrestricted Hartree-Fock equation is solved for the molecular cluster. We also solve for the potential energy surface of the LiH molecule and the Li₂ molecule. We find that the essential features of the hydrogen surface interaction can be understood in terms of the molecule two body interactions. We also find that the hydrogen atom sits below the surface of the Li metal rather than above the surface.     

Effects of the intra-site Coulomb interaction on electron transport in an atom bridge

The effects of the intra-site Coulomb interaction on the electron transport in an atom-sized bridge (an atom bridge) between a metal surface and a tip of a scanning tunneling microscope are investigated with the aid of the Hubbard Hamiltonian. The second-order self-energy with respect to the Coulomb interaction in a single site approximation is taken into account in calculating for the conductance of the bridge. We examine the conductance variation as a function of the stretching length of the bridge in the case where an electron-hole symmetry is broken and two types of the conductance jumps roughly in units of 2e²/h and 4e²/h exist. Numerical results show that a valley structure and a quasi-plateau appear at the upper side of the conductance jumps roughly in units of 4e²/h at low temperatures and at high temperatures, respectively. On the other hand, the reduction of the conductance is small and monotonic at the conductance jumps roughly in units of 2e²/h.     

Potential of interaction of an Ar atom with a proton

The potential of interaction of an Ar atom with a proton is calculated. To verify the result obtained, the wave numbers of the vibrational-rotational spectral lines and the spectroscopic constants for the X¹Σ⁺ state of the ⁴⁰ArH⁺ molecular ion are calculated. The calculated wave numbers of the spectral lines and molecular constants are compared with experimental data.     

The interaction of an atom with a sub-Poissonian single field mode

The resonant interaction of a single atom with a single quantized field mode characterized by sub-Poissonian statistics is compared with its interaction with a coherent field mode. Two models are considered: the Jaynes-Cummings model (JCM) and the Raman-coupled model (RCM). Quadrature squeezing variances and photon number uncertainties are evaluated. In the JCM, sub-Poissonian field statistics lead to longer collapse times and more complete revivals than Poissonian statistics. In the RCM, which is characterized by periodic collapses and revivals, the collapse time is longer for sub-Poissonian fields.This work was supported in part by the UK Science and Engineering Research Council.     

On the self-trapping of an electron due to lattice interaction

The problem of the sharpness of the polaron self-trapping transition for a single electron placed in the conduction band of an insulator and interacting with the phonons of the underlying lattice is investigated within the Fröhlich Hamiltonian. It is shown that this phenomenon depends sensitively on the lattice dimensionality, the nature of the electron-phonon coupling, the nature of the phonon dispersion; and on the discrete or the continuum nature of the applicable Hamiltonian.     

Inelastic processes in the interaction of an atom with an ultrashort electromagnetic pulse

Electron transitions occurring during the interaction of a heavy relativistic atom with a spatially inhomogeneous ultrashort electromagnetic pulse are considered by solving the Dirac equation. The corresponding transition probabilities are expressed in terms of known inelastic atomic form factors, which are widely used in the theory of relativistic collisions between charged particles and atoms. By way of example, the inelastic processes accompanying the interaction of ultrashort pulses with hydrogen-like atoms are considered. The probabilities of ionization and production of a bound-free electron-positron pair on a bare nucleus, which are accompanied by the formation of a hydrogen-like atom in the final state and a positron in the continuum, are calculated. The developed technique makes it possible to take into account exactly not only the spatial inhomogeneity of an ultrashort electromagnetic pulse, but also the magnetic interaction.     

Three-body interaction between an atom and a monolayer film

An atom (B) situated near a plane of atoms (A) experiences an interaction potential energy V = (V₂ + V₃ + … The leading term is the sum over the monlayer of 2-body interactions. We compute here the 3-body correction V₃. Numerical results are presented for the case of noble gases, H and CH₄. For H or He near a Xe layer, V₃ reduces the well depth by ~ 10%.     

Oscillation correction to the electron density of an atom

The oscillation correction to the electron density of an atom in the Thomas-Fermi model is calculated with the help of the method of Green's functions and continuous integration. This correction has a nonanalytic dependence on Planck's constant and cannot be obtained by the usual methods, which employ an expansion in terms of a small parameter proportional to .The author is deeply grateful to L. Ya. Kobelev for suggesting this subject and supervising the work.     

Kerr介质中纠缠原子与非简并双光子相互作用的动力学

考虑了在位于充满Kerr介质的腔中,一对纠缠的二能级原子之一与非简并双光子的相互作用,当该原子离开腔被作选测性测量时,分析测量后光场的量子性质,研究结果表明,在纠缠度一定时,Kerr效应使光场平均光子数的崩塌回复周期减小,光场的二阶相干度减弱,使Cauchy-Schwartz不等式关联程度减弱.     

On the interaction between a vacancy and self-interstitial atom clusters in metals

Atomic-scale computer simulation is used to study the interaction between a vacancy and a cluster of self-interstitial atoms in metals with hcp, fcc and bcc crystal structure: α-zirconium, copper and α-iron. Effects of cluster size, atomic structure, dislocation nature of the cluster side and temperature are investigated. A vacancy can recombine with any interstitial in small clusters and this does not affect cluster mobility. With increasing sizes clusters develop dislocation character and their interaction with vacancies depends on whether the cluster sides dissociate into partial dislocations. A vacancy recombines only on undissociated sides and corners created with undissociated segments. Vacancies inside the cluster perimeter do not recombine but restrict cluster mobility. Temperature enhances recombination by either increasing the number of recombination sites or assisting vacancy diffusion towards such sites. The results are discussed with relevance to differences in irradiation microstructure evolution of bcc, fcc and hcp metals and higher level theoretical modelling techniques.     

Calculation of the potential energy of the interaction of an electron with a molecule

We set forth a mathematically correct algorithm, simple in computer realization, for calculation of the potential energy of the interaction of an electron with a molecule and for the calculation of electric 2^L-pole molecular moments in the framework of the Hartee-Fock-Roothaan method. The proposed method permits consideration of the dynamics of the problem of the dependence of the energy on oscillatory motion in the molecule.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 30–33, August, 1987.     

Self-consistent equations for the interaction of an atom with an electromagnetic field of arbitrary intensity

A system of equations is suggested for the interaction of an atom with an electromagnetic field of arbitrary intensity. The distinctive feature of the equations is that, in the absence of the field, the electron density in the atom is determined by the Schrödinger equation and, in the presence of the field, by the equation resembling the classical equation for an electron in the Lorentz force field.     

Energy lost by an electron beam in interaction with a plasma

Measurements of the electron beam distribution function after the beam has interacted with a plasma, indicate that a large fraction of the energy lost by the beam has been absorbed by the plasma. Only a small fraction is in the wave field.     

Model of the interaction potential of an atom with a hard corrugated surface incorporating a stationary potential well

We propose a new atom-surface interaction potential model which is designed for use in the recent exact theory for the elastic scattering of an atom by a hard corrugated surface model which incorporates a stationary attractive potential well [N. García, F.O. Goodman, V. Celli and N.R. Hill, Phys. Rev. B (1979)]. The model parameters are adjusted to obtain a best-fit to all available experimental data on atom-surface bound-state energies, and comparisons are also made with the latest theoretical data, with satisfactory results.     

The interaction between an atom and a surface at large separation

A simple expression is generated for the coefficient C₃ of the asymptotic dispersion interaction ~z^?3 between an atom and a surface. The basis of the derivation is the assumption of simple forms for the frequency dependence of the polarizability of the atom and the dielectric function of the solid. The expression yields the known value of C₃ within a few percent for all cases for which it has been calculated previously. We use it to generate C₃ values for a large number of systems not previously treated.     

On observing the absence of an atom

An atom is confined to a box in its ground state. An attempt is made to observe it in the left half of the box by scattering photons out of a photon wave packet passing through this half of the box. If no photons are scattered, the atom is missing. It is located on the right side of the box and its wave function is changed. The expectation value of the combined atom and photon energy is increased. For the other alternative, that the atom is found on the left side, the expectation value is decreased. By including both alternatives, it is shown that the mean energy is conserved.     

Emission of an atom during its interaction with an ultrashort pulse of electromagnetic field

The electronic transitions and emission of an atom during its interaction with a spatially inhomogeneous ultrashort pulse of electromagnetic field are considered. The probabilities of excitation and ionization, as well as the spectra and cross sections of reemission of such a pulse by the atom, are obtained. As an example, the one-and two-electron inelastic processes accompanying the interaction of ultrashort pulses with hydrogen-and helium-like atoms are considered.     

Van der Waals interaction between an atom and a surface defect

A continuum dielectric theory is used to investigate the Van der Waals interaction between an atom and a point defect on a planar surface. A vacancy (or adsorbed atom) is modelled by a hemispherical pit (or bump) which perturbs the dielectric response of the defect-free surface. The anisotropy of the interaction is found to be qualitatively different for the vacancy and adsorbate situations. The estimated magnitude of the interaction seems consistent with recent experimental results.