Photodetachment of metal cluster negative ions within many-body theory

The photodetachment cross section and photoelectron angular distribution of metal cluster negative ions are studied theoretically within the consistent many-body theory. Using the Hartree-Fock approximation for the delocalized electrons and the jellium model for the ionic core as the initial approximations, the many-electron correlations are taken into account within the Random Phase Approximation with Exchange. Our calculations demonstrate the dominant role of the many-body effects in the formation of cross sections and angular distributions of photoelectrons emitted from sodium clusters and are in good agreement with the existing experimental data. The concrete comparison of the theory and experiment has been performed for the photoionization of Na7-, Na19-, Na57 anions with entirely closed shells of delocalized electrons

Channeling of ultra-relativistic positrons in bent diamond crystals

Results of numerical simulations of channeling of ultra-relativistic positrons are reported for straight and uniformly bent diamond crystals. The projectile trajectories in a crystal are computed using a newly developed module of the MBN Explorer package which simulates classical trajectories in a crystalline medium by integrating the relativistic equations of motion with account for the interaction between the projectile and the crystal atoms. The Monte Carlo method is employed to sample the incoming positrons and to account for thermal vibrations of the crystal atoms. The channeling parameters and emission spectra of incident positrons with a projecti le energy of 855 MeV along C(110) crystallographic planes are calculated for different bending radii of the crystal. Two features of the emission spectrum associated with positron oscillations in a channel and synchrotron radiation are studied as a function of crystal curvature