Infrared photodissociation spectroscopy of Agn(C6H6)m and Agn(C6D6)m clusters: evidence of adsorption-induced symmetry reduction in benzene

The infrared photodissociation spectra of Agn(C6H6)m and Agn(C6D6)m have been recorded near 10 μm for n = 3–7. For Agn(C6H6)m, we observe a feature around 1032 cm−1, which is assigned to the allowed elu fundamental of benzene. In addition, features are observed near 986 cm−1 in Agn(C6H6)m and 938 cm−1 in Agn(C6D6)m. These bands are assigned to the a1g CC breathing mode - a transition which, while forbiddenfor a gas-phase benzene, is dipole allowed for benzene whose symmetry is reduced (to C6v or lower) by adsorption.