Excitation of theBΠg3states ofN2by electron impact

Radiative lifetime measurements of 13 vibrational levels of the $B{}_{}{}^3{}_{}{}^{}\Pi _g^{}{}_{}{}^{}$ state of ${\mathrm{N}}_2$ have been obtained at 50 eV incident electron energy and 30 mTorr ${\mathrm{N}}_2$ gas pressure using a 50-μsec electron excitation pulse. Two radiative decay components with lifetimes of approximately 5 and 25 μsec are observed in each case. The short-lived component is identified as the contribution from direct excitation of the $B{}_{}{}^3{}_{}{}^{}\Pi _g^{}{}_{}{}^{}$ state. The long-lived cascade contribution is observed to decrease from 37% of the total $B{}_{}{}^3{}_{}{}^{}\Pi _g^{}{}_{}{}^{}\to A{}_{}{}^3{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}(v^{\prime }, v^{\prime \prime })$ radiation for the $v^{\prime }=0\mathrm{}$ vibrational level to 15% for the $v^{\prime }=12\mathrm{}$ level and is consistent with theoretical predictions by Cartwright et al.