Excitation of Atomic Hydrogen by Fast Protons

Abstract

The excitation of the metastable state ($2S$) of atomic hydrogen by fast protons is discussed. The direct excitation cross section of $2S$ is calculated from a coupled set of equations ($1S, 2S, 2P$). The indirect population of the $2S$ state by excitation to higher states with subsequent cascade to the $2S$ state is described by Born approximation. The calculation is shown to apply to a fast crossed beam experiment.