Knowledge Bank

NCO was produced in a low-pressure flow system by reacting HNCO with F atoms generated in a discharge in $CF4/He$. Utilizing a Nd:YAG-pumped dye laser, excitation spectra of the $A2\Sigma +-X2\Pi 1$ system and the $B2\Pi 1-X2\Pi 1$ system were obtained between $4400-3980\backslash AA$ and $3156-3142\backslash AA$ respectively. Signals were read out using a boxear intergrator, which was operated in a scanning mode for lifetime runs. A small monochromator, capable of $1\backslash AA$ resolution, was used to obtain fluorescence spectra. Five vibrational levels (0,0,0; 0,1,0; 1,0,0; 0,2,0; 0,0,1) of the A state were probed, and assignments could be made following Dixon (1). The radiative lifetime was found to be 410 nsec and was insensitive to vibrational level. Quenching rates determined for $N2$ and $O2$ are $3.0\times 10-11$ and $11\times 10-11cm3\sec -1$ respectively. The $R1$ and $R2$ heads of the (0,0,0,-0,0,0) band of the B-X system (2) were pumped, and the resulting fluorescence spectra showed a long Progression in ground state stretching modes. These spectra allowed us to extract a set of constants describing these stretching vibrations in $X2\Pi 1$: $ \begin{array}{lll} \omega^{0}{1}=1286 cm^{-1} & \omega^{0}{3}=1925 cm^{-1} & X_{13} = 27.8 cm^{-1}\ X_{11}=-10.3 cm^{-1} & X_{33}=-11.6 cm^{-1}& \end{array} $ The radiative lifetime obtained for the 8 state was 63 nsec. Quenching rates for $N2$ and $O2$ were found to be $1.3\times 10-10$ and $2.0\times 10-10cm3\sec -1$ respectively.