Doubly excited 2s2p P-1,3(1) resonances in photoionization of helium

The multi-configuration Dirac Fock (MCDF) method is implemented to study doubly excited 2s2p P-1,3(1) resonances of the helium atom and the interference between photoionization and photo excitation autoionization processes. In order to reproduce the total photoionization sprectra, the excited energies from the ground 1s(2) S-1(0) state to the doubly excited 2s2p P-1,3(1) states and the relevant Auger decay rates and widths are calculated in detail. Further more, the interference profile determined by the so-called Fano parameters q and rho(2) is also reproduced. Good agreement is found between the present results and other available theoretical and experimental results. This indeed shows a promising way to investigate the Fano resonances in photoionization of atoms within the MCDF scheme, although there are some discrepancies in the present calculations of the 2s2p P-3(1) state.ational Natural Science Foundation of China 10774122 10876028 China/Ireland Science and Technology Collaboration Research Fund CI-2004-07 Higher Education of China 20070736001 Foundation of Northwest Normal University of China NWNU-KJCXGC-03-2

Radiative electron capture and subsequent radiative decay in collisions of U89+ ions with N-2

To evaluate the radiative electron capture for the collisions of U89+ ion with N-2, radiative recombination cross sections and the corresponding emitted photon energies are calculated from the ground state 1s(2)2s to 1s(2)2snl(j) (2 <= n <= 9, 0 <= l <= 6) using the newly developed relativistic radiative recombination program RERR06 based on the multiconfiguration Dirac-Fock method. The x-ray spectra for radiative electron capture in the collision have been obtained by convolving the radiative recombination cross sections and the Compton profile of N2. Good agreement is found between the calculated and experimental spectra. In addition, the transition energy levels and probabilities among the 147 levels from the captured 1s(2)2snl(j) have been calculated. From the calculated results, radiative decay cascade processes followed by the radiative electron capture have also been studied with the help of multistep model and coupled rate equations, respectively. The present results not only make us understand the details of the radiative electron captures and the radiative decay cascade spectra in the experiment but also show a more efficient way to obtain the cascade spectra. Finally, the equivalence between the multistep model and coupled rate equations has been shown under a proper condition and the latter can hopefully be extended to investigate other cascade processes