Knowledge Bank

A predissociated vibronic progression in the trans-bending ($v3$) mode of HCCH with vibrational origin at $61,340cm-1$ has been observed using the $C~1Ag\leftarrow A¯1Au\leftarrow X~1\Sigma g+$ excitation scheme. We have determined the $C~$ state to be a strongly bent valence state with electron configuration $(lag)2(lbu)2(2ag)2(2bu)2(3ag)2(3bu)2(4ag)2$, and electronic symmetry $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}Ag$. Analysis of the J and K resolved spectra have allowed us to determine the $B\equiv C$ and A rotational constants of this state to be $0.85(6)cm-1$ and $7.5(6)cm-1$ respectively. We are currently recording the spectra of DCCD to obtain bond lengths and angles for this state. The results of these experiments will be presented and the vibrational and J. K-dependence of the predissociation rate will be discussed.