Calculation of the spectroscopic parameters of diatomic van der waals molecules consisting of an inert gas atom and a halogen atom in the ground state

The interatomic potentials in a system consisting of a halogen atom in the ground state and an inert gas atom are calculated by the effective pseudopotential method with a new form of the polarization interaction potential found by calculating the most important polarization diagrams of perturbation theory in the Thomas-Fermi approximation. The results of these calculations of the quasi-molecular terms of this van der Waals system refine available data; some are obtained for the first time. The available experimental and theoretical data are compared. Odessa Hydrometeorological Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 71–75, October, 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 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.     

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.     

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 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.     

Role of a fullerene shell upon stuffed atom polarization potential

We have demonstrated that the polarization of the fullerene shell considerably alters the polarization potential of an atom, stuffed inside a fullerene. This essentially affects the electron elastic scattering phases as well as corresponding cross sections. We illustrate the general trend by particular examples of electron scattering upon endohedrals Ne@C₆₀ and Ar@C₆₀. To obtain the presented results, we have suggested a simplified approach that permits to incorporate the effect of fullerenes polarizability into the Ne@C₆₀ and Ar@C₆₀ polarization potential. By applying this approach, we obtained numeric results that show strong variations in shape and magnitudes of scattering phases and cross sections due to effect of fullerene polarization upon the endohedral polarization potential.     

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.     

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.     

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.     

Radiation loss of electrons under scattering by a Thomas-Fermi atom

A universal theory and calculation results for the bremsstrahlung of electrons on complex atoms are presented. The theory accounts for the dynamic polarization of the core in the energy range from 0.5 to 10 keV, which is characteristic of radiation energy losses in a hot plasma with heavy ions. The treatment is based on the statistical atom model and the quasi-classical approximation of the incident electron. The model accounts for the penetration of the incident electron into the atomic core, which affects the relationship between the polarization and static radiation channels. The contribution of the polarization channel in both the spectral and the total radiation loss of electrons at various frequencies, nucleus charges, and energies of the incident particle is analyzed. It is shown that the contribution of the polarization channel is comparable with that of the static channel (which was calculated elsewhere) in a wide range of parameters. The results obtained are in a reasonable quantitative agreement with the detailed quantum-mechanical calculation carried out for individual atoms.     

极化门控制下中红外激光场驱动He原子产生的单个阿秒脉冲

由中红外激光场（波长为2128nm）驱动He原子,在极化门的控制下,通过强场近似方法(SFA)研究了He原子发射高次谐波的特点.研究表明,在这种组合场驱动下He原子可产生截止位置很高的高次谐波,并且在接近截止位置的平台区展现了超连续的特点,对该超连续部分的高次谐波进行叠加,可得到宽度为44.5as的单个超短脉冲．为了了解该超短阿秒脉冲的产生机理,我们对高次谐波谱的发射过程进行了时频分析,分析表明由于极化门的存在,有效地抑制了极化门以外的阿秒脉冲的发射,从而获得单个阿秒脉冲．     

极化门控制下中红外激光场驱动He原子产生的单个阿秒脉冲

由中红外激光场(波长为2128nm)驱动He原子,在极化门的控制下,通过强场近似方法(SFA)研究了He原子发射高次谐波的特点.研究表明,在这种组合场驱动下He原子可产生截止位置很高的高次谐波,并且在接近截止位置的平台区展现了超连续的特点,对该超连续部分的高次谐波进行叠加,可得到宽度为44.5as的单个超短脉冲.为了了解该超短阿秒脉冲的产生机理,我们对高次谐波谱的发射过程进行了时频分析,分析表明由于极化门的存在,有效地抑制了极化门以外的阿秒脉冲的发射,从而获得单个阿秒脉冲.     

Electron-impact excitation cross sections of gallium atom

Excitation of gallium atom in collisions with slow electrons is studied using the method of extended crossing beams with recording of the optical signal of excited atoms. At an electron energy of 30 eV, 66 excitation cross sections are measured. In the electron energy range of 0–200 eV, 24 excitation optical functions are recorded. The dependence of the cross sections on the principal quantum number of an upper level is obtained for eight spectral series of Ga I. The results obtained are compared with the data of the previous experiment.     

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.     

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.     

Nonlinear optical response of an atom in the field of femtosecond laser pulses with near-atomic intensity

A theory of the nonresonant response of a single atom in a state with arbitrary magnitude and direction of the angular momentum of an atomic electron with respect to the polarization vector of the acting electromagnetic field has been developed. It has been shown that the atomic response current has a tensor structure and depends both on the direction of the angular momentum of the atom and on the polarization vector of the external field. The tensor character of the response is due to the effects of the anisotropy of probability density distribution of the atomic electron as compared to the case of the free atom. The selection rules for the axisymmetric problem of the atom in the field have been analyzed. The manifestation of the selection rules in the angular spectra of photoelectrons has been demonstrated. The probability of the ionization of the atom has been analyzed as a function of the amplitude and duration of the pulse. It has been shown that the width of the generation spectrum is a nonlinear function of the field strength and is saturated in the region of nearly atomic fields. Methods for controlling the parameters of the atomic response spectrum have been proposed on the basis of the use of a sequence of laser pulses with various time profiles, carrier frequencies, and polarization states. It has been shown that the generation of terahertz radiation is possible in the preionization regime, where the generation mechanism is attributed to atomic nonlinearity.     

Integral electronic excitation cross sections of hydrogen atom levels

Bombined results on the integral electron impact excitation cross sections of the 1s → 2s, 2p, 3s, 3p, and 3d transitions in the hydrogen atom obtained on the basis of the global approximation of all available data are presented. The parameters of a four-parameter approximation of the dependence of the excitation cross sections on the electron energy are calculated. Although the values of the cross sections reported in different papers differ by several times, the relative variance obtained by us for the 1s → 2s and 2p transitions is about 25%, while that for the 1s → 3s, 3p, and 3d transitions amounts to 30–40%, which corresponds to the real accuracy for these transitions reported to date. The data obtained on the basis of the global approximation seem to be more reliable than the data of any separate study.