Laser-excited fluorescence of 15NO2 and N18O2

Measurements are reported of the resonance fluorescence of 15N16O2 and 14N18O2 excited by the 488,496, and 514 nm radiation of an Ar+ laser. The frequency displacements in these spectra are consistent with values calculated previously, using potential constants for the electronic ground state of NO2 derived from the rotational and vibrational constants of NO2 and 15N16O2 but containing no information from N18O2 spectra; the agreement obtained for the latter isotope is therefore a partial test of the potential field.In these spectra, fluorescence occurs from vibronic B2 levels of the A2B2 state possessing 7500–8500 cm−1 of vibrational energy. A number of examples are described in which the emission from these vibrationally excited levels shows an anomalous intensity distribution or K-selection rule (e.g., ΔK = ±2) as a result of Coriolis and/or spin–orbit coupling between vibrational levels of the upper electronic state.