Theoretical determination of bound–free absorption cross sections in Ar+2

A b initio calculations have been carried out for the potential energy curves and transition moments of the 2Σ+u, 2Πg, 2Πu, and 2Σ+g states of Ar+2 which arise from the 2P+1S ion–atom asymptote. These data have been used in a theoretical calculation of the dissociative absorption cross sections from the bound 2Σ+u state to the repulsive 2Πg and 2Σ+g states. The 2Σ+u→2Πg transition, which is dominated by spin–orbit effects, has a maximum absorption cross section of 2.6×10−19 cm2 centered at 716 nm with a full width at half-maximum of 185 nm at room temperature. The 2Σ+u→2Σ+g transition is found to be much stronger with a maximum cross section of 0.5×10−16 cm2 centered at 300 nm with a full width at half-maximum of 75 nm at room temperature.