THE DISSOCIATIVE IONIZATION OF HYDROGEN BY FAST HE+ IONS

The energy and angular distribution of fragment protons produced in 5- 25 keV He+-H-2 collisions has been investigated. The fragment protons are found to have energies corresponding (a) to Franck-Condon transiti ons to well known one excited electron repulsive states giving protons with energies of 4-15 eV and (b) especially at energies below 10 keV to two electron autoionizing states which produce protons with energie s less-than-or-equal-to 5 eV. The observed angular distributions show that this latter process occurs predominantly in the C2v conformation in accord with predictions based on a triatomic correlation diagram wh ich indicates that the primary excitation mechanism is an avoided cros sing along with rotational coupling in this conformation.