Variation of electron-NO+-ion recombination coefficient with electron temperature

Abstract

The electron-temperature dependence of the recombination of mass-identified N${\mathrm{O}}^{+}$ ions with electrons is studied by means of a microwave-afterglow/mass-spectrometer apparatus employing microwave heating of the electrons. Under conditions where the N${\mathrm{O}}^{+}$-ion wall current satisfactorily tracks the volume electron density decay, the electron decay data indicate that the recombination coefficient, $\alpha \left(\mathrm{N}{\mathrm{O}}^{+}\right)$, decreases as $T_e^{-(0.37\mathrm{}\pm 0.03)}$ over the range $380\le T_e\le 5470$ K with $T_{+}=T_n=380\mathrm{}$ K. The values of $\alpha \left(\mathrm{N}{\mathrm{O}}^{+}\right)$ obtained at $T_e=T_{+}=T_n=300\mathrm{} \mathrm{and} 380$ K are (${4.3}^7$±0.3)×${10}^{-7\mathrm{}}$ and (${3.5}^0$±0.3)×${10}^{-7\mathrm{}}$ ${\mathrm{cm}}^3$/sec, respectively. These values apply to N${\mathrm{O}}^{+}$ ions in their ground electronic and probably the $v=1\mathrm{} or 0$ vibration state, and are in good agreement with previous afterglow measurements. Our $T_e^{-0.37\mathrm{}}$ variation agrees qualitatively with theoretical predictions of a $\sim T_e^{-0.5\mathrm{}}$ variation, but is not in agreement with the $\sim T_e^{-0.83\mathrm{}}$ variation obtained for N${\mathrm{O}}^{+}$ ($v=0\mathrm{}$) ions using ion-storage techniques. We are unable to account for the discrepancies in the energy dependences obtained in the two measurements.