Photofragment translational spectroscopy of 1,3-butadiene and 1,3-butadiene-1,1,4,4-d4 at 193 nm

The photodissociation dynamics of 1,3-butadiene at 193 nm have been investigated with photofragment translational spectroscopy coupled with product photoionization using tunable VUV synchrotron radiation. Five product channels are evident from this study: C4H5 + H, C3H3 + CH3, C2H3 + C2H3, C4H4 + H-2, and C2H4 + C2H2. The translational energy (P(Er)) distributions suggest that these channels result from internal conversion to the ground electronic state followed by dissociation. To investigate the dissociation dynamics in more detail, further studies were carried out using 1,3-butadiene-1,1,4,4-d(4). Branching ratios were determined for the channels listed above, as well as relative branching ratios for the isotopomeric species produced from 1,3-butadiene-1,1,4,4-d4 dissociation. C3H3 + CH3 is found to be the dominant channel, followed by C4H5 + H and C2H4 + C2H2, for which the yields are approximately equal. The dominance of the C3H3 + CH3 channel shows that isomerization to 1,2-butadiene followed by dissociation is facile.