Photoionisation of the tropyl radical

We present a study on the photoionisation of the cycloheptatrienyl (tropyl) radical, C(7)H(7), using tunable vacuum ultraviolet synchrotron radiation. Tropyl is generated by flash pyrolysis from bitropyl. Ions and electrons are detected in coincidence, permitting us to record mass-selected photoelectron spectra. The threshold photoelectron spectrum of tropyl, corresponding to the X(+ 1)A(1)’ ← X (2)E(2)” transition, reveals an ionisation energy of 6.23 ± 0.02 eV, in good agreement with Rydberg extrapolations, but slightly lower than the value derived from earlier photoelectron spectra. Several vibrations can be resolved and are reassigned to the C–C stretch mode ν(16)(+) and to a combination of ν(16)(+) with the ring breathing mode ν(2)(+). Above 10.55 eV dissociative photoionisation of tropyl is observed, leading to the formation of C(5)H(5)(+) and C(2)H(2).