INNER-SHELL PHOTOIONIZATION OF BERYLLIUM

K-shell photoionization cross sections for Be were calculated by the R-matrix method in a close-coupling approximation using 16-, 17-, and 29-term target representations. Extensive configuration mixing was used to represent the target states so that their energies agreed closely with experiment. As a result the present ab initio calculation reproduces accurately the observed features of the photoelectron spectrum and allows its interpretation; it highlights the significance of direct and conjugate shakeup, especially at low energies, where conjugate shakeup has been found to be important. The calculated partial photoionization cross sections for the three major decay channels with an open K shell closely match recent experiments in magnitude and shape. Our representation of the Be+ target spans 9.8 Ry and is particularly suited for a discussion of highly excited states of Be.