Photoionization cross-section calculations for 4d10 subshell of In in the RPAE

Photoionization cross-section and angular distribution of photoelectrons for 4d¹⁰ subshell of In are calculated in the Random Phase Approximation with Exchange (RPAE). The cross section is in satisfactory agreement with the recent experimental data by Stanford synchrotron.     

Photoionization cross section of 4d10 Xe,Cs and Ba subshells with account of electron shell rearrangement

It is demonstrated that the account, along with many-electron correlations in RPAE method, of the electron shell rearrangement in the process of photoionization, permits to achieve a reasonable agreement between theory and experiment for the 4d¹⁰ subshell cross sections of Xe, Cs and Ba atoms.     

The effect of many-electron correlations on the alignment of ions in atomic photoionization

It is shown that the inclusion of many-electron correlations and electron shell rearrangement can significantly change the alignment of the ion arising from the photoionization of atomic subshells with $\text{j >}\text{1}\text{2}$. The degree of alignment for photoionization of the 4d¹⁰ subshells of Xe, Cs and Ba atoms and the 5p⁶ subshell of Ba is calculated.     

Generalization of the RPAE: 4d-photoabsorption in atomic Ba including relaxation effects

Allowing for monopole polarization of the 5p⁶ shell we find that the RPAE 4d-? f¹P photoionization cross section is very strongly modified between threshold and 1 Ry above. The shape of the calculated modified cross section agrees quite well will experiment.     

Calculation of the photoionization cross sections for the ions of the rubidium isoelectronic sequence by the Dirac-Fock method

The photoionization cross sections for the ground and some excited states of 11 ions of the rubidium isoelectronic sequence from Rb through Ag¹⁰⁺ are calculated by the relativistic Dirac-Fock self-consistent field method. The energy dependence of the photoionization cross sections and the changes in the threshold values along the isoelectronic sequence are considered. The influence of the exchange effect and the choice of gauge on the calculated values of photoionization cross sections is examined. For practical use, the calculated cross sections are approximated by an analytical expression. Along with the total photoionization cross sections, the asymmetry parameter in the angular distribution of photoelectrons and the degree of their polarization are also calculated.     

Application of the second—order ground—state correlation and random—phase approximation on photoionization cross section of manganese

Using the many-body perturbation theory,we have calculated the photoionization cross section of 3p and 3d subshells of the neutral manganese,and discussed the second-order ground-state correlation and random-phase approx-imation correlations in detail.This is the first theoretical calculation for manganese as far as we know .our calculated results are more consistent with the experimental results than those given by other methods in the literature.     

Effect of relativistic many-electron interactions on photoelectron partial wave probabilities

We obtain relative cross sections for the production of photoelectrons with specific angular momentum quantum numbers. These cross sections are obtained from the polarization analysis of the visible fluorescence of ions produced when circularly polarized vacuum ultraviolet radiation photoionizes ground state Ar. The ratio of cross sections for the production of photoelectrons with the same orbital angular momentum but different total angular momenta shows strong deviations from the statistical ratio, demonstrating the importance of relativistic interactions in many-electron photoionization dynamics.     

Photoionization Cross Section and Resonance Structure of Mn+

A photoionization cross section calculation of Mn⁺ is performed in the formalism of many-body perturbation theory for photon energies ranging from 48 eV to 56 eV. We consider excitations from the 3p, 3d, and 4s subshells. The effects of the strong 3p→3d and 3p→4s transitions are included as resonant contributions to the total cross sections. Good agreement with experiment is found.     

Spectroscopy of He–Ne afterglow plasma

Implementation of promising control schemes for the intensity and position of X-ray-laser beams with a photon energy up to several tens of kiloelectronvolts requires knowledge of the angular dependence of cross sections for photoionization of noble gas atoms by hard photons. Estimates of quadrupole corrections to the cross section for photoionization of a Kr atom by X-ray photons with an energy of about 25 keV are reported in this paper. An analytic expression for the cross section of the process is parameterized in a compact form convenient for analyzing angular distributions with an arbitrary polarization of a photon beam.     

Photoionization of onion-type atoms

The photoionization of a two-shell (“onion“) endohedral A@C_N1@C_N2 is considered. The effect of the fullerenes shells upon photoelectron from atom A is taken into account substituting the action of the fullerene by two zero-thickness “bubble potentials.“ The fullerenes shells polarization is included assuming that the radius of the outer shell R ₂ is much bigger than the inner R ₁ and both much exceed the atomic radius r. The interaction between shells C_N1 and C_N2 is taken into account in the Random Phase Approximation (RPA). The effect of photoelectron scattering by both “bubble potentials“ is included in the RPA frame. As concrete examples, two endohedrals Ar@C₆₀@C₂₄₀ and Xe@C₆₀@C₂₄₀ are considered. We investigate 3p4 Ar and 5p Xe subshells.     

Atomic magneto-dipole photoionization

The special features of magneto-dipole photoionization of atomic s states are analyzed and the possibilities of experimental observation of this effect are discussed. It has been shown that despite the smallness of total cross sections for magnetic processes as compared with electric-dipole ones, the experimental observation of magnetic effects is possible, in principle, if photoelectrons are detected in the directions perpendicular to both the polarization vector of photon and its momentum; i.e. in the directions where the differential cross section for electric-dipole ionization of atomic s states is close to zero. The capabilities of the derived general formulas for the magneto-dipole cross sections are illustrated by numerical calculations for s subshells of He and Be atoms.     

Calculation of the photoionization cross section of the 4d10 subshell of the La atom

The photoionization cross section of 4d¹⁰ subshell of La atom is calculated. The cross section curve near its threshold is strongly modified by rearrangement of outer shells in the process of photoionization.     

Theory of spin polarization phenomena in atomic and molecular photoeffects

A compact invariant expression for the angular distribution of photoelectrons formed as a result of photoionization of axisymmetrically polarized atoms and molecules, including optically active molecules, is derived from the general symmetry considerations and using a recently developed bipolar harmonic reduction technique. In the angular distribution of photoelectrons, as well as in the total photoionization cross section, the dependence on all the geometric parameters is separated completely. The polarization of ionizing radiation can be arbitrary, with the partial polarization being specified by the Stokes parameters. The expression for the angular distribution of photoelectrons escaping from an atomic-molecular system oriented in the first order also determines the structure of the expression for the photoionization cross section of an unpolarized system with allowance for the spin polarization of a photoelectron or a photoion with the spin 1/2. The roles played by circular dichroism, chirality, etc., in the process of photoionization of oriented and aligned systems are analyzed in detail.     

高离化态Au离子光电离过程的理论研究

基于多组态Dirac-Fock方法的程序包GRASP92和RATIP及在此基础上最新发展的RELPHOTO08程序, 系统地研究了高离化态金离子M壳层的光电离截面随入射光子能量、 离化度以及壳层的变化规律。结果表明: 光电离截面随光子能量的增大而单调减小; 电离nl电子时, 如果相关电子的主量子数较大, 则该电子存在与否对其光电离截面几乎没有影响; 在同一离化度下, 角量子数l可引起两种性质不同的效应, 其相互竞争可导致光电离截面随入射光子能量的复杂变化。Based on multiconfiguration Dirac Fock method and the corresponding packages GRASP92 and RATIP, as well as the newly developed RELPHOTO08, the variations of M subshell photoionization cross sections with the photon energy, ionization degree and subshells for highly charged gold ions are studied systemically. The present results show that the cross sections are decreasing monotonously with the photon energy; for the photoionization of nl electrons, if the principal quantum number of removed electron is large enough, the cross sections are essentially unchanged upon the presence or absence of outer electrons; for same ionization degree, the angular quantum number introduces two opposite effects which could exist simultaneously, and the intricate variations of cross sections with the photon energy originate from the competition between these two different effects.     

Inelastic scattering of fast electrons from metastable states of helium

Inelastic scattering cross sections for collisions of electrons with helium atoms in metastable 2 ^1,3 S states are calculated for some final states of S and P symmetry by using the First Born Approximation and the Random Phase Approximation. The results for the total cross sections compare reasonably well with previous accurate values in the case of singlet-singlet transitions.     

Theoretical determination of oscillator strengths for the principal series of rubidium-like ions by the Dirac-Fock method

A simple formula that allows the determination of the oscillator strengths for all transitions of principal series of the Rb-like ions is obtained from the relationship between the oscillator strengths and the corresponding photoionization cross sections. The photoionization cross sections are calculated by the Dirac-Fock method with allowance for the retardation and approximated by an analytic formula. The data for ten ions of the rubidium isoelectronic sequence (from Sr⁺ to Ag¹⁰⁺) are presented. Two types of gauges corresponding to the transition operators in length and velocity forms are considered.     

相对论小分量波函数对原子光电离截面的影响

利用相对论平均自洽场理论,　研究了相对论波函数的小分量对原子光电离截面的影响。原子核尺寸效应将使波函数小分量对原子光电离截面的影响减弱。由于波函数沿径向空间被压缩,　电子离核的平均半径较小,　波函数小分量对高离化态离子光电离截面的影响比对一般原子要强得多。波函数小分量反映了相对论效应的基本特征,　从而也定性地说明了光电离过程中相对论效应的强弱。The effects of relativistic small radial component on atomic photoionization cross sections have been studied within relativistic average self consistent field theory. Relativistic effects are relatively unimportant for low photon energy, along with a review of high energy photoionization the relativistic effects are quite important. The effects of relativistic small radial component on photoionization process should show breakdown when the nuclear finite size effects is taken into account. The compression of wavefunction into the space near nucleus is so strong in highly charged ions that the electronic radius greatly decreases, and the effects of relativistic small radial component on photoionization cross sections turn to stronger than ordinary atoms. Since relativistic effects are extremely sensitive to the behavior of small radial component, the results are in good agreement with relativistic effects on photoionization cross section.     

Elastic scattering of an electron by the negative lithium ion

In the framework of the many-body theory, the differential and total cross sections of elastic scattering of slow electrons by the negative lithium ion Li⁻ are obtained. Calculations are performed both in the Hartree-Fock single-particle approximation and with regard to many-electron correlations, which take into account the dynamic polarization of the core. Features observed in the behavior of the phases and cross sections for p and d partial waves are associated with resonance scattering of electron waves. Considering the dynamic polarization of the core by an incident electron heightens the diffraction character of the scattering. The real process is compared with particle scattering in models with a repulsive potential.     

Schematicity and ground state correlations in the lead isotopes

The relationship between collectivity and ground state correlations is analyzed for the single closed shell lead isotopes. The effects of the schematic approximation are discussed, within the framework of both the quasiparticle Random Phase Approximation and the quasiparticle Tamm-Dancoff approach. The consistency of the RPA is investigated.