Angular distribution of electrons from collisionally produced autodetaching states ofH−

The angular distributions of electrons emitted in the decay of the autodetaching $\left(2\mathrm{}{s}^2\right){}_{}{}^1{}_{}{}^{}S$, $\left(2s2p\right){}_{}{}^3{}_{}{}^{}P$, $\left(2\mathrm{}{p}^2\right){}_{}{}^1{}_{}{}^{}D$, and $\left(2s2p\right){}_{}{}^1{}_{}{}^{}P$ states of ${\mathrm{H}}^{-}$ have been measured from 10° to 150° for collisions of ${\mathrm{H}}^{-}$ on He, Ar, and ${\mathrm{H}}_2$ between 100 eV and 10 keV. The intensity of the $\left(2\mathrm{}{s}^2\right){}_{}{}^1{}_{}{}^{}S$ line, in the "rest" reference frame of ${\mathrm{H}}^{-}$, was isotropic for high collision energies. For low-energy collisions the distribution has a component which is asymmetric about 90° and peaked at forward angles. The intensity of the $\left(2s2p\right){}_{}{}^3{}_{}{}^{}P$ line, observed only in high-energy collisions, was approximately isotropic. The intensity of the unresolved $\left(2\mathrm{}{p}^2\right){}_{}{}^1{}_{}{}^{}D$ and $\left(2s2p\right){}_{}{}^1{}_{}{}^{}P$ lines, for collisions above 1 keV, was symmetric about 90° exhibiting a ($1+C {cos}^2\theta$) behavior with angle. For lower collision energies, the angular distribution of the unresolved $\left(2\mathrm{}{p}^2\right) {}_{}{}^1{}_{}{}^{}D-\left(2s2p\right) {}_{}{}^1{}_{}{}^{}P$ lines became asymmetric. The results are interpreted in terms of the orientation of the excited ${\mathrm{H}}^{-}$ state. We discuss the effect of interference between discrete and continuum states and the effect of molecular distortion due to the target atom on the measured angular distribution.