NONRESONANT EXCESS PHOTON DETACHMENT OF NEGATIVE HYDROGEN-IONS

We report the first observation of nonresonant excess photon absorptio n (for ionization as well as detachment) in competition with the singl e photon process. A 35 keV negative hydrogen ion beam is irradiated wi th focused Nd:YAC laser pulses: the 1.165 eV photon energy exceeds the electron binding energy by 0.41 eV. The time of flight spectrum of de tached electrons exhibits the absorption of one and two photons. The d etached electrons exit with a P wave angular distribution for the one- photon detachment and primarily a D wave for the two photon excess pho ton detachment.