Electron-impact detachment from negative ions

Abstract

Electron-impact detachment cross sections have been measured from threshold to about 30 eV for ${\mathrm{D}}^{\mathrm{\ensuremath{-}}}$ and ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$. The purpose was to investigate the cross section near threshold and to reinvestigate earlier claims of resonances due to short-lived states of the doubly charged negative ion. Initial results for ${\mathrm{D}}^{\mathrm{\ensuremath{-}}}$ showed no resonances [L. H. Andersen, D. Mathur, H. T. Schmidt, and L. Vejby-Christensen, Phys. Rev. Lett. 74, 892 (1995)]. Here we show that there is no detectable resonance structure for ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$ either. The applied experimental technique is discussed in detail. Classical and semiclassical models for the detachment process are presented and compared with the data. \textcopyright{} 1996 The American Physical Society.