The photodissociation of propargyl radical, , and its perdeuterated isotopolog was investigated using photofragment translational spectroscopy. Propargyl radicals were produced by photolysis of allene entrained in a molecular beam expansion and then photodissociated at . Photofragment time-of-flight spectra were measured at a series of laboratory angles using electron impact ionization coupled to a mass spectrometer. Data for ion masses corresponding to , , , and the analogous deuterated species show that both H and loss occur. The translational energy distributions for these processes have average values and , respectively, and are consistent with dissociation on the ground state following internal conversion, with no exit barrier for H loss but a tight transition state for loss. Our translational energy distribution for H atom loss is similar to that in a previous work on propargyl in which the H atom, rather than the heavy fragment, was detected. The branching ratio for H loss/ loss was determined to be , in good agreement with previous calculations.
REFERENCES
It should be noted that the most recent high-level calculations on propargyl radical yield a heat of formation of (Ref. 29), a value of greater than the value suggested by Nguyen et al. However, no revised heats of formation for the propargyl fragments were given.
