RANDOM PHASE APPROXIMATION WITH EXCHANGE FOR THE INNER-SHELL ELECTRON PHOTOIONIZATION

Abstract:

We have developed a random phase approximation with exchange (RPAE) method to study the inner-shell electron excitation and photoionization of an open-shell atom or ion. The equations for the dipole matrix element and Coulomb matrix element are derived using the second quantization method and checked against previous formulas by reducing them to those for the case of a single open shell or a closed shell. A computer code has been written to perform the RPAE calculation of the inner-shell photoionization processes. Our RPAE method has been used to calculate the photoionization cross sections of the 4d–ɛf, so called Giant resonance for the atom I and ions Xe⁺ and I⁺. The ground states and core wave functions of Xe⁺, I and I⁺ are obtained through self-consistent Hartree–Fock calculations. The radial functions of the continuum electron are determined by solving the linear HF equations. Finally the following states for Xe⁺ and I are included in the calculations,

The following states are included in the I⁺ calculations, Our results for the Xe⁺ and I⁺ 4d– ɛf transitions agree excellently with the measurements. However, the peak cross section of the I are about three to four times higher than the experimental maximum. We recommend a remeasurement of the I 4d Giant resonance with a careful experimental arrangement.