Zero electron kinetic energy spectroscopy of the para-fluorotoluene cation

Zero electron kinetic energy (ZEKE) spectroscopy is employed to gain information on the vibrational energy levels of the para-fluorotoluene (pFT) cation. Vibrationally resolved spectra are obtained following excitation through a range of intermediate vibrational energy levels in the S-1 state. These spectra allow the observation of different cationic vibrational modes, whose assignment is achieved both from a knowledge of the S-1 vibrational states and also by comparison with density functional calculations. In one notable case, clean ZEKE spectra were obtained from two overlapped S-1 features. From the authors' data, the adiabatic ionization energy of pFT was derived as 70 946 +/- 4 cm(-1). The information on the cationic energy levels obtained will be useful in untangling the intramolecular vibrational redistribution dynamics of pFT in the S-1 state. (c) 2007 American Institute of Physics.