Vacuum Ultraviolet Emission Produced by Proton and H-Atom Impact onH2

Abstract

The spectrum in the wavelength range 1200 to 1700 Å excited by proton and hydrogen-atom collisions with hydrogen molecules has been investigated under thin-target conditions. The prominent features of the spectrum are bands originating from the $B$ and $C$ states of ${\mathrm{H}}_2$ and the Lyman $\alpha$ line of atomic hydrogen. Relative cross sections are presented for the emission of Lyman $\alpha$ and the Lyman band emission from the $B$ state of ${\mathrm{H}}_2$ due to proton and hydrogen-atom impact in the energy range 20-130 keV. Absolute values of these cross sections are estimated by comparison with known cross sections for Lyman $\alpha$. A calculation of the cross section for proton excitation of the sum of the $B$ and $C$ states of ${\mathrm{H}}_2$ in the first Born approximation is presented and compared with the experimental results for the $B$ state.