Formation of Ar2 + ions in cold argon plasmas through the ternary recombination mechanism

A general scheme for calculating ternary recombination rate constants of atomic species based on a hybrid quantum-classical nonadiabatic dynamics approach is presented and applied to a specific case of the ternary recombination of atomic ions of argon in cold argon plasmas. Rate constants are reported for both fine-structure states of the Ar$^+$ ion, $^2P_{3/2}$ and $^2P_{1/2}$, $T = 300$ K, and selected values of the reduced electric field. A thorough comparison with literature data available for $T=300$ K and a couple of close temperatures is performed with a favorable agreement achieved. It is shown that the excited Ar$^+(^2P_{1/2})$ ions may contribute to the formation of dimer ions, Ar$_2^+$, as efficiently as the ground-state ions, Ar$^+(^2P_{3/2})$, due to fast internal conversion of the electronic energy which takes place in ternary collision complexes, Ar$^+$/Ar/Ar.