LIFETIME MEASUREMENT OF ENERGY RESOLVED $NO_{2}$ FLUORESCENCE

Author Institution: Department of Chemistry, Columbia UniversityWith a pulsed narrow-band (0.1 {\AA}) tunable dye laser, $NO_{2}$ fluorescence has been excited in the region 5850 - 5950 {\AA}. By placing the $NO_{2}$ cell inside the resonant cavity of the laser, a 3/4-M Spex spectrometer can be used to energy resolve the fluorescence. The $NO_{2}$ fluorescence in a near collision-free environment ($<$ 1 mtorr) consists of structural features superimposed on an apparent continuum. By directly observing the fluorescence decay, it is found that the structural features have a considerably shorter lifetime $(\sim 10-30 \mu sec)$ than the apparent continuum $(\sim 70 \mu sec)$. Moreover, the lifetime of the structural features show large fluctuations as a function of excitation wavelength. The nature of the excited electronic states involved and their coupling will be discussed