A selective photo-induced reaction in the ion-molecule complex Mg+–FCH3

We have produced cation–molecule complexes Mg+–(FCH3)n (n=0–6) in a laser-ablation pickup source. A photo-induced reaction in Mg+–FCH3 was observed for the first time, with an exclusive production of CH3+ and MgF. This reaction selectivity is remarkable considering the fact that other product channels (CH3+ MgF+) and (Mg++FCH3) are much more energetically favorable. We have measured the relative photodissociation product yield as a function of the excitation wavelength in a broad spectral region. The reaction mechanism is considered to involve a curve crossing to an ionic PES, leading to the formation of the final products CH3+ and MgF.