B-spline R-matrix Calculations for Photoionization of the Be-isoelectronic Sequence

Abstract

We use the B-spline R-matrix (BSR) method to calculate the photoionization cross sections for the seven lightest members in the four-electron Be sequence. For these light ions, we employ the non-relativistic $LS$-coupling scheme, and we report the cross sections of the $^1$S$^e$ ground state over the range of incident photon energies from the first ionization threshold of the ion to its $1s^23d$ ionization threshold for each ion. We demonstrate the validity and the accuracy of the BSR method by comparing the results of our calculations with those of previous calculations and with experimental results. We also confirm that the problem of unphysical pseudo-resonances can be avoided in the BSR method.