Photodissociation Processes of acetylene via 9-10 eV Two-Photon Resonant States

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Ohio State University

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The photodissociation processes of acetylene via 9-10 eV two-photon energy levels have been studied by dispersed emission and the two-color photofragment excitation spectrum. Experimental results indicate that two dissociation channels have been detected: most (>90\%) excited acetylene molecules undergo sequential bond cleavage to yield vibrationally and rotationally hot $C_{2}\cdot(d^{3}\Pi_{g}, A ^{1}\Pi_{u}$) and hydrogen atoms, whereas the remaining fraction of molecules undergoes some geometric rearrangement promptly after the two-photon excitation; in the latter case, subsequent excitation leads to concertive bond ruptures to form $C_{2}\cdot(C^{1}\pi_{g}, A^{1}\Pi_{g})$ and $H_{2}$. The intermediate state, assigned to be $C_{2}H_{3}$, in the sequential bond breakage has a lifetime $2.5,\pm 0.2 \mu s$.


fax \#: 886-2-3620200, bitnet \#: w46a1001@twnmoe01 The geometry of the two-photon resonant states deduced from the photofragment excitation spectrum will be discussed
Author Institution: Institute of Atomic and Molecular Sciences Academia Sinica P. O. Box 23-166, Taipei, Taiwan, R.O.C., and Department of Chemistry, National Taiwan University