FLUORESCENCE LIFETIMES OF THE $\tilde{B}^{2}A'$ STATE OF CCH

Abstract

Three vibrational levels of the $\tilde{B}^{2}A^{\prime}$ state of CCH have been observed by laser-induced fluorescence. They were assigned as $T_{1}$ T+775, and T+1221 where level T was first identified as a vibrational level of the $\tilde{B}$ $state.^{a}$ J, K-resolved fluorescence lifetimes of these vibrational levels of the $\tilde{B}$ state have been determined in a supersonic molecular beam. It was found that the lifetimes of levels T+775 and T+1221 were significantly shorter than that of level T. Lifetimes of various ro-vibrational levels will be presented. The previously reported CC-H bond energies range from 95.6 to 116.3 kcal/$mol,^{b}$ resulting difficulty in assigning the onset of the dissociation process, $CCH(\tilde{X}^{2}\Sigma)\rightarrow C_{2}({X}^{2}\Sigma_{g})+H(^{2}S_{1/2})$. We speculated that lifetimes quenched at levels T+775 and T+1221 were due to predissoication. Comparison of $D_{0}^{0}(CC-H)$ estimated from this work and other literature values will be given.