Photoinduced charge transfer in the Zn-methanol cation studied with selected-ion photofragment imaging

The Zn⁺(methanol) ion molecule complex produced by laser vaporization is studied with photofragment imaging at 280 and 266 nm. Photodissociation produces the methanol cation CH₃OH⁺ via excitation of a charge-transfer excited state. Surprisingly, excitation of bound excited states produces the same fragment via a curve crossing prior to separation of products. Significant kinetic energy release is detected at both wavelengths with isotropic angular distributions. Similar experiments are conducted on the perdeuterated methanol complex. The Zn⁺ cation is a minor product channel that also exhibits significant kinetic energy release. An energetic cycle using the ionization energies of zinc and methanol together with the kinetic energy release produces an upper limit on the Zn⁺-methanol bond energy of 33.7 ± 4.2 kcal/mol (1.46 ± 0.18 eV).