The infrared spectrum of Al+–benzene in the gas phase

The Al–benzene complex is produced by laser vaporization in a pulsed nozzle source. It is ionized with an ArF excimer laser (193 nm), and the Al+(benzene) ions are stored in a quadrupole ion trap. Infrared excitation with a tunable free electron laser induces multiphoton photodissociation, and fragment ions are analyzed by a time-of-flight mass spectrometer. The infrared spectrum of Al+(benzene) is measured with resonance-enhanced multiphoton photodissociation (IR-REMPD) spectroscopy. Bands in the 600–1800 cm−1 region correspond to benzene vibrations shifted by the metal bonding. The spectrum indicates that Al+ binds in the symmetric η6π configuration on the benzene molecule.