EMISSION, ABSORPTION AND QUANTUM YIELDS IN THE $C_{2}N_{2} A^{1}\Sigma^{-} \leftarrow {^{1}}\Sigma^{+}$ TRANSITION

Abstract

Author Institution: Department of Chemistry, Howard University WashingtonWe have measured the absorption, emission end photodissociation spectra of cyanogen in the 220 and 210 nm regions near the $4_{O}{^{1}}$ and $1_{O}{^{1}}4_{O}{^{1}}$ bands of the $A^{1}\Sigma^{-} \leftarrow x^{1}\Sigma^{+}$ system. The spectra were excited with a frequency doubled Nd-YAG pumped dye laser. The doubled light was Reman shifted in high pressures of hydrogen gas. Emission spectra were measured by an unfiltered VUV photomultiplier. The emission spectra did not show all lines that appeared in the absorption spectra and almost all of the intensity was in the $1_{O}{^{n}}4_{O}{^{1}}$ progression. The radiative lifetime of the emission was 660 ns. We used laser induced fluorescence to measure the relative yield of CN radicals as a function of photolysis wavelength. Above the dissociation threshold the yield generally followed the absorption spectrum. A few nascent quantum state distributions of CN were measured. Energy in the CN fragments appeared to be statistically distributed. These results can be understood if some of the excited $C_{2}N_{2}$ is crossing over into a non-dissociating triplet manifold. We are attempting to establish quantum yields for dissociation and emission. If possible fluorescence spectra will also be measured. Dispersed fluorescence spectra will identify the emitting state