Low-energy electron emission in proton-helium collisions.

We have measured doubly differential cross sections for slow electrons emitted in collisions of H[sup +] on He at 100 and 200 keV. The electron energy comprised the range from 1 to 16 eV. We present a detailed account of the experimental steps followed in order to obtain confidence in the data. Two features in the angular distribution of the low-energy electron emission were observed: a strong forward-backward asymmetry that gets smaller at higher projectile energy, and a minimum around [theta]=120[degree].