One- and two-photon detachment of O-

Cross sections for one- and two-photon detachment of O-(1s(2)2s(2)2p(5) P-2(o)) have been determined in a joint experimental and theoretical study. The absolute measurement is based on the animated-crossed-beam technique, which is extended to the case of pulsed lasers, pulsed ion beams, and multiphoton detachment. The ab initio calculations employ R-matrix Floquet theory, with simple descriptions of the initial bound state and the residual oxygen atom which reproduce well the electron affinity and ground-state polarizability. For one-photon detachment, the measured and computed cross sections are in good mutual agreement, departing significantly from previous reference experiments and calculations. The generalized two-photon detachment cross section, measured at the Nd: YAG laser wavelength, is in good agreement with the R-matrix Floquet calculations. Long-standing discrepancies between theory and experiment are thus resolved.