LASER-INDUCED FLUORESCENCE STUDIES OF C3 FORMATION AND ISOMERIZATION IN THE 193 NM PHOTOLYSIS OF ALLENE AND PROPYNE

The quantum state distributions of the C3 radical from the UV multipho ton dissociation of allene and propyne in a pulsed molecular beam have been measured. The observed distributions for both molecules are iden tical and are much colder than a phase space model would predict, impl ying that direct dissociation is occurring in one step and isomerizati on in another. It is concluded that both allene and propyne undergo in ternal conversion from the S1 state to the vibrationally excited S0 gr ound state of allene followed by molecular elimination of H-2. The obs erved C3 is then produced by molecular elimination of H-2 from the sec ondary photolysis of C3H2.