Representation of electronic wavefunctions by Lobatto shape functions: application to the photoionization cross section of H⁺ ₂

It is shown that a convenient and flexible representation of molecular electronic continuum wavefunctions may be constructed from Lobatto shape functions, especially in combination with conventional Gaussian-type basis functions. When used in the logarithmic derivative version of the Kohn variational principle, an efficient procedure for calculating molecular photoionization cross sections is obtained. As a first example, the method is applied to the benchmark system H⁺ ₂. Excellent results are found with rather moderate effort for the full investigated range of photoelectron energies (up to 200 eV).