ISOTOPE EFFECTS IN THE AUTOIONIZATION OF SUPEREXCITED 1-SIGMA-U+ (Q1)STATES IN HYDROGEN

The kinetic energy spectra of the fragment protons and deuterons produ ced in the dissociative photoionization of H-2 and D2 by 27.5 32.0 eV photons have been measured. It is shown that the results can provide a n experimental estimate of the autoionizing state width of the 1SIGMA( u)(1) superexcited state as a function of internuclear separation R. T he experimentally determined state widths are significantly larger tha n theoretical predictions especially at large R. Furthermore there is an unexpectedly large isotope effect.