K-Shell Ionization ofN2and CH4by 50- to 600-keVH+,D+,H2+, andHe+Impact

Abstract

A crossed-beam scattering chamber was used to measure absolute cross sections for Auger-electron ejection by 50- to 600-keV ${\mathrm{H}}^{+}$, ${\mathrm{D}}^{+}$, $\mathrm{H}_{2}^{}{}_{}{}^{+}$, and ${\mathrm{He}}^{+}$ impact on ${\mathrm{N}}_{2}$ and C${\mathrm{H}}_{4}$. Auger electrons emitted at 150\ifmmode^\circ\else\textdegree\fi{} with respect to the incident ions were analyzed by an electrostatic parallel-plate spectrometer with a resolution of 1.1% full width at half-maximum. The intensities of Auger-satellite lines were determined to study the simultaneous inner- and outer-shell ionization of ${\mathrm{N}}_{2}$ by $\mathrm{H}_{2}^{}{}_{}{}^{+}$ and ${\mathrm{He}}^{+}$ at different energies. The Auger spectra were integrated with respect to energy and angle of ejection of the electrons to obtain total cross sections for $K$-shell ionization. The experimental results are compared with existing theories. Good agreement is obtained for ${\mathrm{H}}^{+}$, ${\mathrm{D}}^{+}$, and $\mathrm{H}_{2}^{}{}_{}{}^{+}$, but discrepancies appear for ${\mathrm{He}}^{+}$ impact at low energies. Ratios of Auger-electron and x-ray production cross sections are determined to study the effect of multiple ionization on the fluorescence yield.