Recombination of electrons withNH4+·(NH3)n-series ions

The recombination coefficients $\alpha$ of ${\mathrm{N}{\mathrm{H}}_4}^{+}·{\left(\mathrm{N}{\mathrm{H}}_3\right)}_n$ series ions for $n=0\mathrm{} \mathrm{to} 4$ have been determined using a microwave afterglow-mass-spectrometer apparatus. For $\mathrm{NH}_4^{}{}_{}{}^{+}$ ions, under conditions where the electron, ion, and neutral temperatures are equal ($T_e=T_{+}=T_n$), $\alpha \left({18}^{+}\right)=(2.5\mathrm{}\pm 1), (1.5\mathrm{}\pm 0.3) \mathrm{and} (1.3\mathrm{}\pm 0.2)\times {10}^{-6\mathrm{}}$, ${\mathrm{cm}}^3$/sec at 200, 300, and 410 K, respectively. The electron-temperature dependences of the recombination coefficients for the first and second cluster ions are found to be (in ${\mathrm{cm}}^3$/sec) $\alpha \left({35}^{+}\right)=2.82\mathrm{}\times {10}^{-6\mathrm{}}{\left[\frac{300}{T_e\mathrm{}\left(K\right)\mathrm{}}\right]}^{0.147}$ and $\alpha \left({52}^{+}\right)=2.68\mathrm{}\times {10}^{-6\mathrm{}}{\left[\frac{300}{T_e\mathrm{}\left(K\right)\mathrm{}}\right]}^{0.050}$, accurate to ± 10% over the range $300\le T_e\le 3000$ K. At 200 K, the third and fourth clusters yield $\alpha \left({69}^{+}\right)=\alpha \left({86}^{+}\right)=(3\mathrm{}\pm 1)\times {10}^{-6\mathrm{}}$ ${\mathrm{cm}}^3$/sec. A new recombination mechanism, cluster-detachment recombination, is postulated to account for the very weak variation of $\alpha$ with electron temperature observed for the (${35}^{+}$) and (${52}^{+}$) ions.