Auger width and branching ratios for berylliumlike 1s2s²np¹P^o and 1s2p³¹P^o resonances and photoionization of beryllium from 1s²2s²¹S

The photoionization cross section (PICS) of Be from the ground state is studied with the saddle-point complex-rotation method for photon energies from 25 to 122 eV. A full-core plus correlation wave function is used for the ground state. For the resonances in the continuum, the energy and width for the singly core-excited Be-like 1s2s²2p¹P^o, 1s2p³¹P^o, and 1s2s²3p¹P^o are calculated to high precision. The PICS are studied with a single open-channel approximation as well as fully coupled open channels. The Auger decay branching ratios of these states are studied to check the spin-alignment theory recently proposed by Chung. These results are compared with the existing theoretical and experimental data in the literature. For beryllium, our energy and width of 1s2s²2p are 115.513 eV and 36.6 meV and those of 1s2s²3p are 121.420 eV and 50.4 meV, which agree with the experiment of Caldwell et al., [Phys. Rev. A 51, 542 (1990)].