The possibility to separate Auger transitions to different repulsive doubly charged final ion states by measuring the photo- and the Auger -electrons in coincidence in the molecular frame is demonstrated.
Photoionization cross sections for the outer shell of the nitrogen atom ground state are calculated in the single-particle Hartree–Fock approximation and, in order to take into account many-electron correlations, also in the Random Phase Approximation with Exchange (RPAE). To be able to apply the RPAE, its modification for the half-filled shell atom, such as nitrogen atom, is presented. Calculation of length and velocity forms of the cross section in both approximations are compared with the available experimental data, and a good agreement is obtained. It has been found that in the RPAE the influence of many-electron correlations in a nitrogen atom is not great, but it is very important since, in contrast to the Hartree–Fock approximation, it results in the validity of the sum rule and the coincidence of the length and velocity forms of the cross sections, in agreement with the requirement of the general theory. The angular distribution of photoelectrons is also calculated in the RPAE, which has not been measured so far.
It is shown that recently discovered effects of magnetic x-ray dichroism in angular-resolved photoemission from core levels of ferromagnets appear due to the spin-orbit and exchange splitting of core levels. The effects are proportional to the state multipoles characterizing the alignment and orientation of the hole levels, and can be observed with circularly polarized, linearly polarized, and unpolarized light. Possible applications of these effects in investigations of magnetic structures and adsorbates are pointed out.
Photoionization cross sections, dipole matrix elements and phase shifts are calculated for the O K-shell of the CO molecule using two theoretical models. One of them is a new version of the relaxed core Hartree–Fock approximation with a fractional charge. The value of this charge is considered as a fitting parameter. In this paper, the fractional charge 0.7 was used which gives a correct position of the maximum of the σ* shape resonance in the photoionization cross section. The other model is a modification of the multiple scattering method with overlapping atomic spheres. The dipole matrix elements and phase shift differences calculated by these two methods are compared with the corresponding values determined from the complete experiment by Cherepkov et al (2000 J. Phys. B: At. Mol. Opt. Phys. 33 4213).
Partial and total photoionization cross sections of ${\mathrm{N}}_{2}$ molecule are calculated using the generalization of the random-phase approximation (RPA) which earlier has been successfully applied to the description of the atomic photoionization processes. According to this method, at first the Hartree-Fock (HF) ground-state wave functions are calculated in prolate spheroidal coordinates using the fixed-nuclei approximation. With their help the zero order basis set of single particle Hartree-Fock wave functions containing both discrete excited states and continuous spectrum is calculated in the field of a frozen core of a singly charged ion. The calculations are performed for all four valence shells of ${\mathrm{N}}_{2}$ molecule, $3{\ensuremath{\sigma}}_{g},$ $1{\ensuremath{\pi}}_{u},$ $2{\ensuremath{\sigma}}_{u},$ and $2{\ensuremath{\sigma}}_{g},$ with the intershell correlations fully taken into account within the RPA method. It is demonstrated that different intershell correlations, especially between three outer shells, play an important role in photoionization process. Examples of the influence of intershell correlations on several transitions are presented. Partial and total photoionization cross sections of ${\mathrm{N}}_{2}$ molecule obtained by this method in the photon energy range from ionization threshold up to 70 eV are in a good agreement with the existing experimental data and with the recent RPA calculations [Cacelli et al., Phys. Rev. A 57, 1895 (1998)].
The generalized oscillator strengths for the transitions from the ground state to the excited discrete and continuous states of the beryllium atom are calculated in the framework of the random-phase approximation with exchange for a range of momentum transfer values from 0 to 3 a.u. The results for the 2s→2p transition are compared with calculations of Sinanoglu and Davis and good agreement is obtained. Also the influence of electron correlation is examined for the transitions to the lowest excited states in the discrete and continuous spectrum, as for these transitions the influence is strongest.
The alignment of Au + ions following L3 photoionization has been studied using ah igh-resolution x-ray spectrometer. We observed a small anisotropy for the angular dependence of Au Lι and Lα emissions. The alignment parameter A20 derived from the experimental results is compared with theoretical calculations by Hartree–Fock approximation and random phase approximation with exchange. The contribution to the alignment of quadrupole interaction is discussed.
Abstract We have developed the Hartree‐Fock jellium model for deformed metal clusters by treating the quantized electron motion in the field of the spheroidal ionic jellium background in the Hartree‐Fock approximation. Using this model, we have calculated single electron energy levels as a function of the cluster deformation parameter for a series of sodium clusters with the number of atoms N in a cluster ranging from 4 to 40. We have established that the cluster deformations corresponding to the minimum total energy of the oblate and prolate clusters are in reasonable agreement with the experimental data and the predictions of other theoretical models.
