The photodetachment cross section of the negative hydrogen ion

The photoionization cross section of the hydrogen negative ion is computed using a discrete-basis-set expansion to represent both the ground and continuum states of the system. This discrete-basis-set representation is used to construct an approximation to the dynamic polarizability, which in turn is used in an analytical continuation procedure for complex values of the frequency. This "discretization" of the continuum makes the method potentially applicable to larger systems, and a study of the basis-set dependence is made. The final results are in good agreement with more elaborate calculations and with experimental results. The dynamic polarizability in the normal dispersion region is also computed.