Calculation of photoionization cross sections by the absorbing boundary method

A new method for the calculation of quantum state decay rates, the absorbing boundary method (ABM), has recently been developed. In this talk the general form of the ABM will be outlined. The pseudo bound state approach to the calculation of continuum rates such as photoionization cross sections and used by Langhoff and coworkers will be briefly reviewed and shown to lack precision in the absence of information about the line widths and shapes of the pseudo bound states. It will then be noted that the ABM can be used to construct a rigorous new approach to the calculation of photoionization cross sections incorporating the necessary lifetime information for the pseudo bound states while still allowing the computation to be carried out by bound state procedures.