LASER-INDUCED FLUORESCENCE STUDIES OF THE A-X AND B-X SYSTEMS OF THE NCO RADICAL

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 Title: LASER-INDUCED FLUORESCENCE STUDIES OF THE A-X AND B-X SYSTEMS OF THE NCO RADICAL Creators: Sullivan, Brian J.; Smith, Gregory P.; Crosley, David R. Issue Date: 1982 Publisher: Ohio State University Abstract: NCO was produced in a low-pressure flow system by reacting HNCO with F atoms generated in a discharge in $CF_{4}/He$. Utilizing a Nd:YAG-pumped dye laser, excitation spectra of the $A^{2}\Sigma^{+}-X^{2}\Pi_{1}$ system and the $B^{2}\Pi_{1}-X^{2}\Pi_{1}$ system were obtained between $4400-3980 \AA$ and $3156-3142 \AA$ respectively. Signals were read out using a boxear intergrator, which was operated in a scanning mode for lifetime runs. A small monochromator, capable of $1 \AA$ 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 $N_{2}$ and $O_{2}$ are $3.0 \times 10^{-11}$ and $11 \times 10^{-11} cm^{3} \sec^{-1}$ respectively. The $R_{1}$ and $R_{2}$ 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 $X^{2}\Pi_{1}$: $\begin{array}{lll} \omega^{0}_{1}=1286 cm^{-1} & \omega^{0}_{3}=1925 cm^{-1} & X_{13} = 27.8 cm^{-1}\\ X_{11}=-10.3 cm^{-1} & X_{33}=-11.6 cm^{-1}& \end{array}$ The radiative lifetime obtained for the 8 state was 63 nsec. Quenching rates for $N_{2}$ and $O_{2}$ were found to be $1.3\times 10^{-10}$ and $2.0\times 10^{-10} cm^{3} \sec^{-1}$ respectively. Description: $^{(1)}$R.N.Dixon, Phil. Trans. Roy. Soc. London, A262, 165 (1960). $^{(2)}$R.N. Dixon, Can. J. Phys. 38, 10 (1960). This work was supported by the U. S. Army Research Office. URI: http://hdl.handle.net/1811/29229 Other Identifiers: 1982-RC-8