Photodissociation of the propargyl and propynyl (C3D3) radicals at 248 and 193 nm

The photodissociation of perdeuterated propargyl (D2CCCD) and propynyl (D3CCC) radicals was investigated using fast beam photofragment translational spectroscopy. Radicals were produced from their respective anions by photodetachment at 540 and 450 nm (below and above the electron affinity of propynyl). The radicals were then photodissociated at 248 or 193 nm. The recoiling photofragments were detected in coincidence with a time- and position-sensitive detector. Three channels were observed: D-2 loss, CD+C2D2, and CD3+C-2. Observation of the D loss channel was incompatible with this experiment and was not attempted. Our translational energy distributions for D-2 loss peaked at nonzero translational energy, consistent with ground state dissociation over small (< 1 eV) exit barriers with respect to separated products. Translational energy distributions for the two heavy channels peaked near zero kinetic energy, indicating dissociation on the ground state in the absence of exit barriers.