Studies of Nonresonant Charge Transfer between Atomic Ions and Atoms

Abstract

Measurements of nonresonant charge transfer between atomic ions and atoms have been made in a drift-tube—mass-spectrometer apparatus as a function of $\frac{E}{p}$ (drift field/gas pressure) at 295 K. At $\frac{E}{p}=0\mathrm{}$ the charge-transfer coefficients are: $k({\mathrm{He}}^{+},\mathrm{Hg})=(1.6\mathrm{}\pm 0.3)\times {10}^{-9\mathrm{}}$ ${\mathrm{cm}}^3$/sec, $k({\mathrm{Ar}}^{+},\mathrm{Hg})=(1.52\mathrm{}\pm 0.3)\times {10}^{-11\mathrm{}}$, $k({\mathrm{Kr}}^{+},\mathrm{Hg})=(8.5\mathrm{}\pm 2)\times {10}^{-12\mathrm{}}$. For ${\mathrm{Ne}}^{+}$ + Hg and ${\mathrm{Xe}}^{+}$ + Hg, $k$ is ≤ ${10}^{-12\mathrm{}}$, while for ${\mathrm{He}}^{+}$ + Ne and ${\mathrm{He}}^{+}$ + Ar, $k$ is ≤ ${10}^{-13\mathrm{}}$ ${\mathrm{cm}}^3$/sec. Little dependence of $k({\mathrm{He}}^{+},\mathrm{Hg})$ and $k({\mathrm{Ar}}^{+},\mathrm{Hg})$ on ion energy is found up to mean energies of $\sim 0.25$ eV. Comparison of the measured rates with available theories suggests an inability to predict the moderately slow reaction rates.