The unimolecular dissociation of the molecular ion of acetophenone induced by thermal radiation

The molecular ion of acetophenone is shown to undergo unimolecular dissociation to the benzoyl cation in an ICR cell at low pressures and in the vicinity of 333 K with rate constants in the range of 2 to 4 s −1 . Pressure and temperature dependence of this process reveal that the process is primarily induced by absorption of thermal radiation driving ions to energies above the dissociation limit. Collisional effects also enhance this dissociation by a mechanism that attempts to restore a full Boltzmann distribution of the molecular ions.