The infrared spectrum of the benzoyl cation

The vibrational spectrum of the gas phase benzoyl cation (C6H5CO+) in the 500–2500 cm−1 range is presented. Vapor phase benzoic acid is photolyzed/photoionized using an ArF excimer laser and the resulting ionic fragments are stored in a quadrupole ion trap. The benzoyl cation is subsequently isolated and its infrared spectrum is recorded through multiple photon dissociation spectroscopy with a free electron laser. Density functional calculations predict a C2v structure for the benzoyl cation, which is in good agreement with the observed spectrum.