Radiative Lifetime of theS25Metastable State ofN+

The radiative lifetime of metastable ${\mathrm{N}}^{+}\left({}_{}{}^5{}_{}{}^{}S_2^{}{}_{}{}^{}\right)$ has been measured to be 4.2±0.6 msec, a value generally in agreement with theory, by direct monitoring of the spontaneous emission from ∼ 1$0^6$ ${\mathrm{N}}^{+}$ ions stored in a radio-frequency ion trap. Additional measurements were made of the quenching rate coefficient (2.5×${10}^{-9\mathrm{}}$ ${\mathrm{cm}}^3$ ${\sec }^{-1\mathrm{}}$) and the production cross section (≥ ${10}^{-18\mathrm{}}$ ${\mathrm{cm}}^2$) of ${\mathrm{N}}^{+}\left({}_{}{}^5{}_{}{}^{}S_2^{}{}_{}{}^{}\right)$ in ${\mathrm{N}}_2$. This work supports the interpretation of the 2145-Å feature in the spectrum of aurorae as being due to ${\mathrm{N}}^{+}\left({}_{}{}^5{}_{}{}^{}S_2^{}{}_{}{}^{}\right)$ emission.