Collision destruction of fast metastable hydrogen atoms

A modulated beam technique has been used to investigate the collisional destruction of 10-30 keV 2s metastable hydrogen atoms in passage through hydrogen, helium, neon, argon, krypton and nitrogen. It is shown that, at the impact energies investigated, both electron loss and de-excitation are significant destruction processes and the absolute cross sections for each process have been separately determined. Loss cross sections for metastable atoms, which were found to be approximately a factor of two larger than the corresponding cross sections for ground state hydrogen atoms, are compared with recent theoretical estimates obtained by Bates and his collaborators using a classical impulse approximation. The formation of metastable atoms by charge transfer neutralization of 10-30 keV protons has also been analysed quantitatively using neutralizer gas pressures high enough to obtain equilibration of the beam.