Ionisation of atomic hydrogen by slow He2+ions

A crossed beam method incorporating time-of-flight analysis and coincidence counting of the collision products has been used to measure cross sections for ionisation of atomic hydrogen by alpha particles in the range 18.6-64 keV amu -1 . The results extend measurements previously obtained in this laboratory in the range 31-550 keV amu -1 down to energies significantly below the cross section peak where the limitations of some theoretical descriptions become apparent.