Branching ratio of the H-(n=2) shape resonance.

Abstract

The relative photodetachment cross section for decay into the H(N=2) channel by the $^{1}$P\ifmmode^\circ\else\textdegree\fi{} shape resonance in ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ was measured, as well as that for decay into all channels. The branching ratio \ensuremath{\sigma}(N=2)/\ensuremath{\sigma}(total) was computed for a series of energies between 10.95 and 11.3 eV after normalizing the cross sections to theoretical peak amplitudes. The maximum branching ratio (\ensuremath{\approxeq}0.8) appears at an energy about 20 meV higher than the central energy of the resonance. Results are compared with recent theoretical calculations.