Measurement of (00v3) levels in X 2Π NCO by stimulated emission pumping spectroscopy

Laser induced fluorescence measurements of NCO formed in the reaction CN+O2→NCO+O in a free jet expansion are reported. The rotational temperature achieved in the experiments was typically 10--15 K and absorption from vibrationally excited levels was very much reduced in intensity. Two bands in the A--X system, the v1, v2, v3=200--000 and 120--000, of the radical were rotationally resolved for the first time, and wavelength resolved laser excited fluorescence measurements have been used to characterize many ground state vibronic energy levels below 6000 cm-1 in energy. Stimulated emission pumping experiments were carried out on vibronic levels associated with the ν3 vibration with 1≤v3≤3 in the electronic ground state. Harmonic and anharmonic constants were determined, together with the spin--orbit coupling parameters and rotational constants for these levels