Analysis of photon emission from 50--350-keV proton impact onH2O

Abstract

We have measured photon emission cross sections from neutral fragments produced by collisions of 50--350 keV protons with ${\mathrm{H}}_{2}$O molecules. Balmer $\ensuremath{\alpha}\ensuremath{-}\ensuremath{\delta}$ emissions from both the target and projectile were recorded. We also analyzed $A {}^{2}{\ensuremath{\Sigma}}^{+}\ensuremath{-}X {}^{2}\ensuremath{\Pi}$ (0,0) and (1,0) emission from the excited OH fragment produced during target dissociation. Trends in the cross sections revealed two key properties of the collision process: (1) The Bethe theory accurately describes target emission from both H and OH fragments and (2) the ratio of any two Balmer emission cross sections for both the target and projectile can be approximated by simple functions of the respective optical oscillator strengths. Finally, we provide the Bethe fit parameters necessary to calculate the target emission cross sections at all nonrelativistic impact energies.