Photoinduced reactions in the ion-molecule complexes Mg+-XCH3 (X = F, Cl)

The cation-molecule complexes Mg+-(XCH3)(n) (X = F, Cl) were produced in a laser-ablation pickup source. Photoinduced reactions in Mg+-FCH3 and Mg+-ClCH3 were observed, with the dominant or the only products being CH3+ and MgX. We have measured the relative photodissociation product yields as a function of the excitation wavelength for several complexes in a broad spectral region. Experiments on the complexes with different halide substitutions show different photoreaction patterns. In particular, photodissociation of the cationic complex Mg+-FCH3 produced exclusively MgF and CH3+, whereas in Mg+-ClCH3, nonreactive quenching was also observed besides the reactive channel mentioned above. The photodissociation action spectra are discussed with the help of quantum ab initio calculations of both the ground state and the relevant excited-state potential energy surfaces