Infrared photodesorption of methanol molecules adsorbed on a Au-4(+) cluster

The infrared photodissociation of mass selected cluster-adsorbate complexes Au-4(+)(CH3OH)(m) (m = 1-3) is studied in a Penning ion trap. Spectra are obtained by the excitation of vibrational modes of methanol, the desorption of neutral molecules and the detection of fragment ions by time-of-flight mass spectrometry. The photodissociation spectra are red-shifted with respect to the absorption frequency of free methanol. The number of photons necessary for the desorption of the adsorbate molecules and the respective separation energies are estimated.