Chemical reaction pathways and product state correlations of gas-phase ion–molecule reactions are governed by the involved potential energy surfaces (PESs). Here, we report the photodissociation dynamics of charge-transfer complex [Ar–N2]+, which is the intermediate of the model system of the Ar+ + N2 → Ar + N2 + reaction. High-resolution recoiling velocity images of photofragmented N2 and N2 + from different dissociation channels exhibit a vibrational state-specific correlation, revealing the nonadiabatic charge-transfer mechanisms upon the photodissociation of [Ar–N2]+. The state-resolved product branching ratios have yielded an accurate determination of the resonant charge-transfer probabilities. This work provides a powerful approach to elucidating the detailed dynamics of chemical events of charge-transfer complex [Ar–N2]+ and to probing the state-to-state charge-transfer PESs.

The recently constructed cryogenic cylindrical ion trap velocity map imaging spectrometer (CIT-VMI) has been upgraded for coincidence imaging of both ionic and neutral photofragments from photodissociation of ionic species. The prepared ions are cooled down in a home-made cryogenic cylindrical ion trap and then extracted for photodissociation experiments. With the newly designed electric fields for extraction and acceleration, the ion beam can be accelerated to more than 4500 eV, which is necessary for velocity imaging of the neutral photofragments by using the position-sensitive imaging detector. The setup has been tested by the 355 nm photodissociation dynamics of the argon dimer cation (Ar2+). From the recorded experimental images of both neutral Ar and ionic Ar+ fragments, we interpret velocity resolutions of Δv/v≈4.6% for neutral fragments, and Δv/v≈1.5% for ionic fragments, respectively.

No abstract