Investigation of several low-lying levels of X 2Π NCO using argon laser excited fluorescence

The laser excited fluorescence spectrum of NCO from an atmospheric pressure CH4/N2O/N2 flame is reinvestigated with a more sensitive apparatus than used previously. The NCO is pumped from the X 2Π (1,01,0) level to the A 2Σ+ (0, 00, 0) level. Emissions to (0, 01, 0)2Π, (1, 01, 0)2Π, (0, 01, 1)2Π, and (0, 10, 0)2Σ+ in the X state are observed. The previous tentative assignment of pumping transition as Q231 is confirmed. The confirmation of pumping transition solidifies our earlier interpretation that excited state spin relaxation in the flame is much faster than electronic quenching. In addition, analysis of the fluorescence spectra yields the first reported constants for the X(1, 01, 0)2Π level and spin splitting for X(0, 01, 1)2Π level in the gas phase.