Chemi-ionization in collisions of metastable neon with argon

Abstract

Absolute and relative cross sections were obtained for the Penning-ionization (PI) reaction ${\mathrm{Ne}}^{*}+\mathrm{Ar}\ensuremath{\rightarrow}\mathrm{Ne}+{\mathrm{Ar}}^{+}+e$ and the associative-ionization (AI) reaction ${\mathrm{Ne}}^{*}+\mathrm{Ar}\ensuremath{\rightarrow}\mathrm{Ne}{\mathrm{Ar}}^{+}+e$ by a merging-beams technique over a range of interaction energies $W$ from 0.01 to 600 eV. The Ne* represents a composite of $\mathrm{Ne}(3s^{3}P_{2})$ and $\mathrm{Ne}(3s^{3}P_{0})$. The PI cross section ${Q}_{{\mathrm{Ar}}^{+}}$ rises with decreasing $W$ except for a small dip near 0.05 eV and exhibits a rather weak dependence on $W$. For a change of almost five orders of magnitude in $W$, ${Q}_{{\mathrm{Ar}}^{+}}$ only changes by about a factor of 7. The AI cross section ${Q}_{\mathrm{Ne}{\mathrm{Ar}}^{+}}$ monotonically increases with decreasing $W$ and shows a large dependence on $W$. The ${Q}_{\mathrm{Ne}{\mathrm{Ar}}^{+}}$ at $W=0.01$ eV is about 70 times larger than that at 0.5 eV. The total cross section ${Q}_{T}={Q}_{{\mathrm{Ar}}^{+}}+{Q}_{\mathrm{Ne}{\mathrm{Ar}}^{+}}$ is compared with theoretical and other experimental values. At low $W$ our absolute ${Q}_{T}$ are considerably larger than those of Tang, Marcus, and Muschlitz although the relative ${Q}_{T}$ for both experiments are in fair agreement.