State-selected ion–molecule reactions: N+2(v)+H2→N2+H+2 and Ar+(2P J) +H2→Ar+H+2

Charge transfer cross sections for state-selected N+2 (X,A;v) and Ar+(2PJ) ions colliding with H2 have been measured at laboratory energies of 10.5 and 14.5 eV by means of the TPEPICO (threshold-photoelectron/photoion coincidence) method using synchrotron radiation. The cross sections are put on an absolute basis by normalizing to earlier measurements for N+2+H2. For the purpose of comparison total cross sections have also been measured for state-selected H+2(v)+N2 at 10 eV lab. A simple model, which assumes that small impact parameter collisions lead to chemical reaction, gives a qualitative explanation of the N+2+H2 and Ar++H2 data. The work sheds light on previous problems with the application of the principle of microscopic reversibility to these systems.