Zero kinetic energy photoelectron spectra of the allyl radical, C3H5

We present high resolution zero kinetic energy photoelectron spectra of the allyl radical through various intermediate vibronic states. The spectra yield an ionization energy of 65 762 cm(-1), corresponding to 8.153 eV, as well as frequencies for a number of cationic vibrational states. The spectrum from the B 0(0)(0) state shows activity in modes corresponding to out-of-plane motion of the terminal -CH2 groups. This confirms the nonplanar geometry of this state suggested previously, and thus provides additional insight into the vibronic couplings in the intermediate states. (C) 2000 American Institute of Physics. [S0021-9606(00)02326-6].