Electron-impact detachment from negative ions

Electron-impact detachment cross sections have been measured from threshold to about 30 eV for D^- and O^-. 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 D^- 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 O^- either. The applied experimental technique is discussed in detail. Classical and semiclassical models for the detachment process are presented and compared with the data. {} 1996 The American Physical Society.