Electric-field-induced electron detachment of 800-MeV H − ions

The lifetime of 800-MeV ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ ions against electron detachment in a static electric field was measured over a range of eight orders of magnitude in experiments at the High Resolution Atomic Beam Facility of the Los Alamos Meson Physics Facility. The ions traversed a linear gradient magnetic field of 1.3-T peak strength resulting in a 6-MV/cm peak rest-frame electric field capable of stripping a large fraction of ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ ions. The unstripped ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ ions, neutral ${\mathrm{H}}^{0}$ atoms, and protons were detected 5.5 m from the magnet. This spectrum was analyzed to determine the lifetime of the ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ ion versus electric-field strength and the results were compared with previous studies. Three parametrizations of the lifetime formula based on an existing theory were used to calculate the stripping probability. The data were fit to the lifetime formula and good agreement with theoretical predictions was found. Finally, a possible experiment for observing excited states of ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ is briefly discussed.