State-specific reactions and autoionization dynamics of Ar2+ produced by synchrotron radiation

Abstract The long-lived excited states of doubly charged rare gases can markedly affect their reactivity. In this paper we demonstrate the presence of strong state-specific effects in the charge exchange of Ar 2+ ( 3 P, 1 D and 1 S) with several neutral targets (He, Ne, Kr, Xe, D 2 , and CH 4 ). State sensitive measurements have been performed by producing the different Ar 2+ electronic states via tunable synchrotron radiation (Elettra-Trieste, Italy and SuperACO-Orsay, France). From the product ion yield data of charge transfer, state-selected total cross-sections have been deduced. Using the state-specific reactivity of Ar 2+ towards different neutral targets, it has been possible to extract the photon-energy-dependent production branching of the three doubly charged states and to investigate the autoionization dynamics of neutral or singly charged Ar in the vicinity of the double ionization threshold.