CROSSED-BEAM STUDY OF THE H--2-]HD(UPSILON')+D- REARRANGEMENT REACTION IN THE COLLISION ENERGY-RANGE 0.3-3 EV(D)

A crossed beam study of the rearrangement reaction H- + D-2(v = 0) --> HD(v') + D- in the collision energy range E(rel) = 0.3-3 eV is report ed. From the vibrationally state-resolved energy and angular spectra o f the D- product ions, we derive state-specific differential cross sec tions in the CM system. Absolute units are obtained by using elastic H - + He scattering as a reference system. The measurements allow detail ed conclusions concerning the reaction mechanism. By integrating over angles and summing over partial cross sections (for individual v' stat es of the HD product molecule), we determine the absolute total cross section of the reaction. The reaction has a threshold at E(rel) = 0.42 +/- 0.12 eV. The cross section rises to a maximum of 2 x 10(-16) cm(2 ) at 1.5 eV and then rapidly decreases again. The present results reso lve a discrepancy between two previous measurements bearing on the det ermination of the total cross section.