Collisional fragmentation of fast HeH+ ions: The He2++H- channel

We studied the H- production from the dissociation of fast HeH+ projectiles , which occurs only through the He2+ + H- dissociative channel as electron capture is negligible at large velocities. We measured the lateral profiles of the H- ions produced in collisions of HeH+ with We and Ar atoms at velo cities of 2.8, 3.0, and 3.9 a.u. and extracted from them an H- kinetic ener gy distribution in the projectile center-of-mass frame. These results, toge ther with a published internuclear distance distribution measured with a si milar ion source, allowed us to obtain the potential energy curve associate d to this dissociative channel. This energy curve crosses several excited s tates of the HeH2+ and HeH+ ion dissociating into He2+ plus A and He+ plus H, respectively, thereby suggesting;the existence of an inhibition in the H - formation process through transition to these HeH2(+) and the HeH+ states . The presence of this inhibition was corroborated by measuring the H- tota l cross section for He, Ne, and Ar targets and v = 4 a.u. [S1050-2947(99)01 103-8].