Knowledge Bank

Vibrational relaxation in the $A2\Sigma +$ state of the NCO free radical is shown to be slow compared with its radiative lifetime of 170 ns. Excitation into high vibrational levels results in observation of extensive progressions in the ground state $\nu 2$ frequency and permits study of the Renner Teller splitting in the $X2\Pi 3/2$ state. In contrast with the slow overall vibrational relaxation in the A state, the relaxation between levels known to be in Fermi resonance is found to be extremely fast.