Energy Dependence of the 4610- and 4765-Å Lines ofAr+Excited in Low-EnergyHe++Ar Collisions

We have measured the energy dependence of the 4610- and 4765-Å lines of ${\mathrm{Ar}}^{+}$ excited in low-energy ${\mathrm{He}}^{+}$ +Ar collisions from threshold to 700 eV ${\mathrm{He}}^{+}$ energy. The 4610-Å line rises sharply with energy to a peak near threshold, while the rise of the 4765-Å line is more gradual than previously reported and than most other lines excited in this process. The 4765-Å line still shows, however, a much lower energy peak than predicted by the adiabatic hypothesis. The threshold behavior of the 4610- and 4765-Å lines appears to be typical of lines emitted from levels with ${}_{}{}^1{}_{}{}^{}D$ and ${}_{}{}^3{}_{}{}^{}P$ parent terms, respectively.