Evidence for theΔu3→BΠg3Transition inN2

A dc discharge through 2 to 10 Torr of flowing nitrogen gas has been observed with an infrared spectrometer. Eleven molecular bands have been recorded, of which the 4435-, 4134-, 3830-, 3514-, 2998-, 2730-, and 2457-${\mathrm{cm}}^{-1\mathrm{}}$ bands have been assigned to the ${}_{}{}^3{}_{}{}^{}\Delta _u^{}{}_{}{}^{}\to B{}_{}{}^3{}_{}{}^{}\Pi _g^{}{}_{}{}^{}$ system in accordance with the vibrational analysis. Vibrational quantum numbers have been assigned for the observed bands; a potential-energy curve has been computed for the ${}_{}{}^3{}_{}{}^{}\Delta _u^{}{}_{}{}^{}$ state; and a Deslandres and Franck-Condon table has been generated for the band system. The molecular constants calculated for the ${}_{}{}^3{}_{}{}^{}\Delta _u^{}{}_{}{}^{}$ state from the present analysis are: $T_e=59738\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, ${\omega }_e=1539\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, and $x_e{\omega }_e=17\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$. This state is of particular interest because of its relationship with the nitrogen $1PG$ and $2PG$, two prominent systems in most discharges containing air or nitrogen, as well as in the aurora.