Charge transfer dynamics of the Ar+(2P3/2) + N2 reaction at very low collision energies.

The charge transfer reaction Ar+ + N2 → Ar + N2+ has been studied for collision energies of 40, 90, and 170 meV with product energy and angle-differential crossed-beam velocity map imaging. Resonant multi-photon ionization was employed to create the charged reactant Ar+ in the 2P3/2 spin-orbit ground state with high purity. At the lowest studied collision energy of 40 meV, we could observe the N2+ product in the v = 0 vibrational level with a high amount of rotational excitation. This level is strongly dynamically suppressed at higher collision energies, where excited vibrational levels become accessible. In addition, a higher fraction of backward scattering is observed at this low collision energy compared to higher collision energies. This shows that the reaction dynamics of the charge-transfer reaction undergo a profound change from direct to unusual complex-mediated charge transfer dynamics at very low collision energy.