Ab initio multichannel photoionisation of H2: photoelectron angular distribution for rotationally resolved states of H2+

The total integrated and differential cross sections for H2 photoionization were calculated with consideration given to the rotational motion of the initial as well as the residual molecule. In an attempt to perform a completely ab initio study, the final-state wavefunction of the e(-) + H2(+) system was obtained from the polarized-orbital method, and three different wavefunctions for the initial state were used. Photoionization matrix elements were calculated for both length and velocity forms of the electric dipole operator, and the effects of various approximations were evaluated. Results indicate that: (1) S branch observables are extremely sensitive to various approximations; (2) it is necessary to couple partial waves higher than l = 1 in the continuum orbital; (3) it is necessary to include exchange and polarization in the final-state wavefunctions; and (4) the best photoionization quantities are those obtained in the dipole-length approximation.