Single-photon double ionization of He and Ne

Abstract

The photoionization branching ratio for double ionization has been measured from threshold to 800 eV for Ne and from threshold to 560 eV for He. Both sets of data have an initial rise from threshold, in general agreement with other published results, but the Ne data reach a plateau value above threshold in contrast to some of the other measurements and to the He data. The Ne data reach a value of approximately 13%, while the He data approach a value of approximately 4% before decreasing. A plateau in the He data was not reached in our measurements but may exist at higher energies. The photoionization cross section for double ionization has been extracted from the branching-ratio data.