Example: neutralization of negative ions InI₂^– in direct charge transfer collisions with atomic ions In⁺

Processes of ion destruction are important for the balance of charged particles, which directly affects plasma characteristics, such as electric field strength and discharge current, in practically important devices like gas-discharge lasers and luminescence lamps.

A typical example of such processes is mutual neutralization in a direct collision between the positive atomic ion In+ and negative molecular ion InI2–. This neutralization takes place because of nonadiabatic transitions at crossings between the diabatic ionic term Uion(R) and covalent terms Ucov,i(R) (see figure) and can be described by the Landau-Zener model. The probability of the transition between the ionic and covalent state i is low if crossing takes place at short distances, where coupling Vi between the ionic and covalent states is strong (adiabatic limit), and at long distances, where the above coupling is weak (diabatic limit). Therefore, the M states i to which charge can be transferred effectively can be determined by analyzing this figure and calculating couplings Vi.

Specific calculations were performed using the vertical binding energy of the outer electron in InI₂^– found in Kintech Lab by ab initio computations using the GAUSSIAN-03 program package,  energy levels of In available in the literature, and the semiempirical expression for V_i from the work [R.Olson, F.Smith, E.Bauer Appl.Opt. 10, 1846 (1971)]. It was found that only In(5s²5p,²P_3/2) is formed with the rate constant k(T)=1.7´10^-12T^-0.33 cm³/s.

Thus, Kintech Lab expertise in the theory of elementary processes and quantum chemistry allowed us to gain quantitative information about the rate of the practically important process, for which both experimental and theoretical data were unknown.