Photochemical processes on transition metal atoms and small clusters

Reported here are the first results of a new approach to studying the chemistry of metal clusters. Bare metal atoms and clusters complexes with one or two reactant molecules (either ethanol or propanol) are generated in an ion trap where they are excited with radiation from a tuneable infrared laser. Although a single photon of the latter is not sufficient to break a chemical bond, because the clusters spend ≈ 1 ms within the radiation field, they absorb 15–20 photons (1.5–2 meV) which, in some cases, is sufficient to drive a chemical reaction. The photofragment yields exhibit a pronounced dependence on laser wavelength and at least one infrared absorption feature has a peak centre close to that seen for alcohol molecules adsorbed on to the surfaces of metals and metal oxides.