Excitation of the 2p sigma(u) state of H-2(+) as a function of the internuclear axis alignment

H-2 is bombarded by 400-eV electrons. Electrons scattered 18 degrees with a n energy loss of 36 eV are detected in coincidence with 7.6-eV H+ fragments from the 2p sigma(u) state of H-2(+) The collision time and dissociation t ime are very small compared to the rotation time of the molecule. Therefore , the H+ fragments leave the collision region along the line of the internu clear axis at the time of the interaction with the projectile. Angular dist ribution measurements of the H+ ions yield the relative cross section for e xcitation of the 2p sigma(u) state of H-2(+) as a function of orientation o f the internuclear axis. The data show a cosine-squared distribution relati ve to the momentum transfer vector of the collision. Calculations predictin g the angular distribution are performed using prolate spheroidal coordinat es. [S1050-2947(99)04101-3].