Effects of electric fields on the photodetachment cross section of the H- ion near threshold.

Abstract

A study is presented of the photodetachment cross section of the ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ ion near the one-electron threshold in electric fields ranging from approximately 5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$ up to 2.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ a.u. The lowest-field data, nominally at zero field, are consistent with the Wigner threshold law for p-wave processes. At larger field values, photodetachment using \ensuremath{\sigma}-polarized laser light displays the expected lowering of apparent threshold and evidence of tunneling. Using \ensuremath{\pi}-polarized light, the same features are seen with the additional feature of oscillations superimposed on the cross section. Three complementary explanations are presented for the oscillations.