Effects of strong electric fields on resonant structures inH−photodetachment

Relativistic kinematics with an 800-MeV ${\mathrm{H}}^{-}$ beam at the Clinton P. Anderson Meson Physics Facility (LAMPF) at Los Alamos allows the observation, with very little background, of resonant structures in the photodetachment spectrum of ${\mathrm{H}}^{-}$ in intense electric fields. We report studies of the ${}_{}{}^1{}_{}{}^{}P$ resonances near $n=2\mathrm{}$ in ${\mathrm{H}}^{-}$ in electric fields as high as 1.3 MV/cm. The splitting of the ${}_{}{}^1{}_{}{}^{}P$ Feshbach resonance can be explained by Stark mixing with a nearly degenerate ${}_{}{}^1{}_{}{}^{}S$ resonance. For field values above those required to quench the Feshbach resonances a ${}_{}{}^1{}_{}{}^{}D$ state is observed, apparently induced by Stark mixing with the ${}_{}{}^1{}_{}{}^{}P$ shape resonance. The systematics of the behavior of these resonances are compared with the results of a simple perturbation model.