Measurements of Threshold Behavior for One- and Two-Electron Photodetachment from the H exp - Ion

摘要

One and two-electron photodetachment from the H exp - ion by a single photon has been studied using a crossed beam apparatus. A Q-switched laser beam was directed across the 800 MeV H exp - beam at LAMPF ( beta =0.842) resulting in Doppler-shifted photon energies in the H exp - barycentric frame, which were tunable from 0.4 eV to 15.5 eV by changing the intersection angle. The particles (e exp - , H exp 0 , H exp + ) resulting from photodetachment reactions were magnetically deflected into scintillation detectors allowing the total and partial cross sections for 1e exp - and 2e exp - processes to be separately measured. The 2e exp - signal (H exp + ) was produced by two different mechanisms, the true signal gamma + H exp - implies H exp + + 2e exp - and the background process gamma + H exp - implies H exp 0 (n), followed by motional electric field ionization of excited H exp 0 . Two-electron photodetachment which had been predicted theoretically was observed for the first time, and the relative cross section was measured from threshold to 15.5 eV. (ERA citation 07:012715)