Degenerate autoionization processes in the photoionization of molecular hydrogen

Abstract

The contribution of both autoionization and direct ionization processes to the photoionization continuum of hydrogen has been examined experimentally in order to ascertain the relative importance of the above two processes, to determine the final state to which a particular autoionizing Rydberg state decays, and to see if there are any preferred routes for the two types of processes. Autoionization processes which produce electrons with energies in the range 0 to 0.003 eV, so-called degenerate autoionization processes, have been studied here by means of a new type of threshold electron analyzer which has an identically zero transmission probability for energetic electrons. It was found that degenerate autoionization processes are not uncommon and that there is a preference in such autoionization processes for J=K between the ground state hydrogen molecule and the final state of the molecular ion. Direct ionization also appears to be favored for J=K. The detailed routes of several degenerate autoionization processes are examined and other inferences made.