Calculation of the spectroscopic parameters of van der waals diatomic molecules: An excited alkali Na or K atom and an inert gas atom

The interatomic potentials in a system of an excited Na or K atom and an inert gas atom are calculated on the basis of the effective pseudopotential method, using a new form of the polarization interaction potential obtained by calculating the most important polarization diagrams of perturbation theory in the Thomas-Fermi approximation. The results of a calculation, on its basis, of the intermolecular terms of this van der Waals system are given, refining the existing data; some of the results have been obtained for the first time. A comparison is made with the available experimental and theoretical data. Odessa Hydrometeorological Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 32–35, September, 1996.     

Calculation of spectroscopic parameters of diatomic van der walls molecules: Inert gas atom-halogen atom

Based on the effective pseudopotential method with the use of a new form of the polarization interaction potential that is obtained from calculating the major polarization diagrams of perturbation theory in the Thomas-Fermi approximation a calculation of interatomic potentials in the “halogen atom in the ground state F—inert gas atom Br” system is performed. The results of calculating on its basis the quasimolecular terms of the sought van der Waals system that ascertain the available data are given. Comparison with the available experimental and theoretical data is made. Odessa Hydrometeorological Institute, 15, L'vovskaya St., Odessa, 270016. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 256–259, March–April, 1997.     

Calculation of the interaction potential for excited alkali element atoms with the mercury atom. Rb*-Hg interaction

Using a new form for the polarization interaction potential obtained by calculating the most important polarization diagrams of perturbation theory in the Thomas — Fermi approximation, the pseudopotential method is employed to calculate interatomic potentials in a system alkali element in ground and excited states — mercury atom. Calculations of quasimolecular terms based on this technique are presented for the system A-Hg, where A = Na, Rb, some for the first time. A comparison is made to available experimental and theoretical data.Odessa Hydrometeorological Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 31–38, June, 1994.     

Nonlinear polarization response of a gaseous medium in the regime of atom stabilization in a strong radiation field

The nonlinear polarization response of a quantum system modeling a silver atom in the field of high-intensity radiation in the IR and UV spectral ranges has been studied by direct numerical integration of a nonstationary Schrödinger equation. The domains of applicability of perturbation theory and polarization expansion in powers of the field intensity are determined. The contribution of excited atoms and electrons in a continuum to the atomic polarization response at the field frequency, which arises due to the radiation-induced excitation and photoionization processes, is analyzed. Features of the nonlinear response to an external field under conditions of atom stabilization are considered.     

串接型三能级原子的感应极化

从求在双频场作用下的三能级原子系统的哈密顿量的本征函数和本征值出发,导出系统随时间的演化规律.从而得出宏观极化的表示式.计算了极化的频谱分布和它们的相对强度.     

Calculation of the spectroscopic characteristics of biatomic van der Waals molecules and ions: Inert gas atom — halogen-type inert gas ion in the ground state

The interatomic potentials in a system formed by an ion of an inert gas in the ground state and an atom of an inert gas (e.g., Ne⁺, Ar⁺-Ne, Ar, Kr, Xe) are calculated on the basis of a calculation of the most important polarization diagrams of perturbation theory in the Thomas-Fermi approximation. The calculation employs the effective pseudopotential method using a new form of the polarization interaction potential. Results are presented from a calculation of the quasimolecular terms of particular van der Waals systems that improve existing data; some of the data were obtained in earlier studies. Odessa Hydrometeorological Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 36–40, March, 1998.     

Phonon dispersion on Ag(100) surface:A modified analytic embedded atom method study

Within the harmonic approximation, the analytic expression of the dynamical matrix is derived based on the modified analytic embedded atom method(MAEAM) and the dynamics theory of surface lattice. The surface phonon dispersions along three major symmetry directionsΓˉXˉ, Γˉ Mˉ, and Xˉ Mˉ are calculated for the clean Ag(100) surface by using our derived formulas. We then discuss the polarization and localization of surface modes at points Xˉ and Mˉ by plotting the squared polarization vectors as a function of the layer index. The phonon frequencies of the surface modes calculated by MAEAM are compared with the available experimental and other theoretical data. It is found that the present results are generally in agreement with the referenced experimental or theoretical results, with a maximum deviation of 10.4%. The agreement shows that the modified analytic embedded atom method is a reasonable many-body potential model to quickly describe the surface lattice vibration. It also lays a significant foundation for studying the surface lattice vibration in other metals.     

Transient effects of three photon pulses in resonant two-level atom systems

Using statistical quantum electrodynamics techniques, we compute the polarization of a two-level atom system following three pulses. Homogeneous and inhomogeneous broadening and pulse width are incorporated in the formalism. Phase conjugation by three-photon process is investigated.     

Estimate of the polarization fields of a relativistic atom in a solid

The magnetic and electric polarization fields of a relativistic hydrogen atom in a solid are analyzed. At atomic distances, these fields differ only slightly from the corresponding fields of an ionized atom.     

Control for atom response in multicomponent laser fields

A theory of the nonlinear optical response of an atom interacting with a superposition of arbitrarily polarized fields is developed. The theory is based on the analytical solution of the boundary-value problem for an electron moving in a spherically symmetric intraatomic field and in the field of an external electromagnetic field. By means of the example of an argon atom interacting with a bichromatic field formed by the first and second harmonics of a Ti:sapphire laser, it is shown that, when an atom interacts with the field of two polarized pulses the polarization directions of which are not collinear, the response spectrum significantly depends on the laser radiation parameters—the duration and intensity of pulses, the time of delay between them, and the angle between the directions of polarization vectors. Generation of THz radiation is shown to be possible in the ionization-free regime due to intraatomic nonlinearity.     

The influence of quantum interference effects on the resonance fluorescence spectra of a degenerate three-level atom

The resonance fluorescence spectra of a degenerate three-level atom of the V-type in the field of an intense monochromatic wave with an arbitrary polarization composition are investigated. Analytical expressions are derived for the resonance fluorescence spectra, and the angular distribution of spontaneous fluorescence of atoms is analyzed for the D-line emitted by vapors of alkali atoms. It is shown that the number of lines in the spectrum may decrease in the case of the linear polarization of spontaneous radiation. The radiation relaxation operator is obtained for the D-line of alkali metals in the case when an atom is near the metal surface. Interference effects for such systems are analyzed.     

Polarization fields in the positronium atom undergoing emission or absorption of optical photons

This paper solves the problem of the interaction of an electron and positron via the field of soft and hard photons with emission or absorption of a real photon. The interaction is interpreted as a third-order QED effect in the coordinate representation. The role of intermediate states with positive and negative frequencies is studied. A general expression is derived for the matrix elements of the operator of the effective electron-positron interaction energy for different types of quantum transitions. The expression makes it possible to calculate the probabilities of the corresponding transitions in the nonrelativistic approximation. Electric dipole transitions in the positronium atom accompanied by emission (absorption) of an optical photon are investigated. Two-particle wave functions of the positronium atom are used to introduce the concept of polarization fields inside the positronium atom. It is found that the polarization fields depend on the coordinates and time and on the choice of the pair of states between which a quantum transition with emission or absorption of a photon takes place. Zh. éksp. Teor. Fiz. 113, 471–488 (February 1998)     

Effect of two-level atom on photon packet polarization

A packet of photons interacting with a two-level atom is considered. It is shown that if the atomic dipole momentum transition vector is not parallel to the photon polarization, the linear photon polarization changes into an elliptical one. The upper-bound estimation for the ratio of short and long axes of the ellipse gives 0.2. The phenomenon is of a quantum origin and caused by the action of the atom on the photon packet.     

Resonances in electron-impact integral excitation cross sections of the magnesium atom

The resonance structure of the integral cross sections of excitation of the magnesium atom by low-energy electrons is analyzed in terms of the R-matrix method. The collision strengths are calculated in terms of the close-coupling approximation with consideration of 25 atomic states, including 13 physical target states and 12 pseudostates. The latter simulate the remaining bound and continuum states of the Mg atom that were not included in the close-coupling expansion explicitly. The positions and widths of the resonances found are determined, and the resonances are classified with respect to the mechanism of formation of short-lived states of the negative Mg ion. The results of calculations are compared with available experimental data.     

Binuclear atom as the bound state of a proton and a heavy atom

The existence of a bound state of a proton and a heavy atom is predicted. The atom is described by the Thomas-Fermi method. The electrons screen the field of the proton, which suppresses the repulsive force between the proton and the atomic nucleus. On the other hand, the force of attraction between the proton and the electrons is directed along the electron density gradient (i.e., towards the nucleus). It is concluded that for Z = 80, the two forces are balanced at a distance from the nucleus of about 0.6 of the Bohr radius. It is found that the potential energy minimum of the proton with a depth of several tens of electronvolts lies in the range of negative energies (attraction). It is proposed that such a system be referred to as a binuclear atom. It is emphasized that, in contrast to molecules, in which binding with the hydrogen atom is ensured by a rearrangement of the states of the outer-shell (valence) electrons, a binuclear atom is formed as a result of the collective response of the system of inner electrons to the proton potential.     

Analysis of atom detection via the magnetic optical effect

We demonstrated a new method of atom detection by means of the magnetic optical effect. The number density of the atom cloud was measured by detecting the rotation angle of the polarization plane of linearly polarized probe light when propagating inside the atomic cloud. Detuning, the magnetic field and light intensity dependencies of the rotation angle were studied theoretically and experimentally to find the best parameter for atom detection. In this way, we managed to achieve a rotation angle of 0.22 rad with a signal to noise ratio (SNR) of 75 and a contrast of 87.5%.     

Calculation of the potential of interaction of excited atoms of alkali elements with a mercury atom: A-Hg interaction (A=K,Fr)

The interatomic potentials in the system (alkali atom in the ground and excited states)—((mercury atom) are calculated on the basis of the effective pseudopotential method using a new form of the polarized interaction potential obtained from calculations of the most important polarization patterns of perturbation theory in the Thomas-Fermi approximation. This method is used to calculate the intermolecular terms of the system A-Hg (A=K, Fr), some of which have been obtained previously.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 84–88, January, 1996.     

单个钛原子储氢能力和储氢机制的第一性原理研究

采用基于密度泛函理论的第一性原理方法研究了单个过渡金属钛原子吸附氢分子的物理机制. 研究表明,单个钛原子最多能吸附8对氢分子,吸附结构为对称的两个类金字塔型结构, 其平均吸附能为- 0.28 eV.通过计算轨道能级和差分电荷密度分布,分析决定吸附结构、 吸附能大小以及吸附氢分子数目的内在物理机制.研究表明,钛原子的4s电子转移到3d轨道上, 从而产生较强的极化电场,导致氢分子极化,钛原子通过静电极化作用吸附氢分子. 本文的研究将对设计高密度储氢材料有一定的指导作用.