THE RESONANCE FLUORESCENCE SPECTRUM OF NITROGEN DIOXIDE

Abstract

We have observed with high resolution the resonance fluorescence spectrum of $NO_{2}$ recently reported by Sakurai and Broida (1). With 514.5 nm excitation, the transition obeys the selection rules for a parallel band. The excitation is from the N = 8, K = 4 level of the ground state to an electronic level having N = 9 and K = 4. Three prominent triplets are observed corresponding to transitions to the $v_{2}$, $2v_{2}$, and $3v_{2}$ levels following the selection rule $\Delta N$ = 0 + 1, $\Delta K$ = 0. Our interpretation is supported by observed intensities and by the close agreement of observed displacements and displacements calculated from infrared measurements of Arakawa and Nielsen (2). We interpret these observations as evidence for a $^{2}B_{2}$ electronic state in addition to the $^{1}B_{2}$ state discovered by Douglas and Huber (3) from their U.V. absorption measurements. The existence of a $^{2}B_{2}$ state is in accord with the predictions of Burnelle, May and Gangi (4), e.s.r. observations (5) and the photo dissociation recoil spectrum (6).