Recombination Coefficient of Molecular Rare-Gas Ions

The coefficients relating to the recombination of molecular rare-gas ions with electrons are determined from the slope of the straight part of the curve representing the reciprocal of the electron density as a function of time during the afterglow period of plasmas produced in helium, neon, argon, krypton, and xenon. The results are compared with the machine computation of Gray and Kerr. The influence on the measurements of the magnitude and duration of the plasma excitation pulse was studied. The values of the recombination coefficients obtained are ${\alpha }_r\left({{\mathrm{He}}_2}^{+}\right)<~4\times {10}^{-9\mathrm{}}$, ${\alpha }_r\left({{\mathrm{Ne}}_2}^{+}\right)=(2.2\mathrm{}\pm 0.2)\times {10}^{-7\mathrm{}}$, ${\alpha }_r\left({{\mathrm{Ar}}_2}^{+}\right)=(6.7\mathrm{}\pm 0.5)\times {10}^{-7\mathrm{}}$, ${\alpha }_r\left({{\mathrm{Kr}}_2}^{+}\right)=(1.2+0.1)\mathrm{}\times {10}^{-6\mathrm{}}$, and ${\alpha }_r\left({{\mathrm{Xe}}_2}^{+}\right)=(1.4\mathrm{}\pm 0.1)\times {10}^{-6\mathrm{}}$ ${\mathrm{cm}}^3$ ${\sec }^{-1\mathrm{}}$. The values were independent of gas pressure over the pressure ranges studied. The influence on the measuring technique of the collision frequency for momentum transfer of electrons with gas atoms caused an apparent pressure dependence of the measured recombination coefficient of ${\mathrm{Xe}}_2^{+}$ ions.