Auto transfer to Rydberg states and indirect stabilization following double capture

Abstract

Two-electron capture by slow multiply charged ions colliding on rare-gas targets at keV energies populates doubly excited states of the projectile with large cross sections. Though these states are dominantly autoionizing, important radiative decay following double capture have been reported, among which the direct observation of the fluorescence from Rydberg states. These findings are important since they modify the charge and radiation balance of the multiple charge exchange reactions. A mechanism based on post-collisional effects was proposed, in which Rydberg states are fed from the quasi-symmetrical doubly excited states initially populated. A quantitative analysis of this effect is developed leading to a simple model which is applied to N7+ on He and Ar collisions. The evolution of the competition between autoionization and fluorescence yields of the Rydberg states with the internuclear distance is emphasized.

Double Rydberg States Formed in Stabilized Triple Electron Capture

“…The contribution of argon lines was only a few percent of the total intensity. Ar II lines are due to double captures into asymmetrical configurations followed by recaptures of a Rydberg electron by the target [6] as already observed [15]. The weak Ne VIII 7-8 line at 296.3 nm is attributed to the decay of the Rydberg electron n 0 ¿ n in , n of triply excited ͑n in , n, n 0 ͒ states produced by TTC and by partly autoionizing multielectron captures.…”

“…Contributions of single capture followed by transfer excitation and of other dielectronic interactions for populating asymmetrical configurations [3][4][5] depend on collision systems and impact energies. In the case of primary population into ͑n, n 0 ͒ symmetrical configurations which are strongly mixed with (low n 1 , high n 2 ) Rydberg states, the transfer from the former to the latter by autotransfer to Rydberg states (ATR) is very efficient [6,7]. In a recent paper, we showed that the radiative stabilization of both electrons in double capture is the highest when the asymmetrical Rydberg series ͑3, n͒, ͑4, n͒, and ͑5, n͒ are populated [8].…”

Kinematically complete study of electron transfer and rearrangement processes in slowAr16+-Ne collisions

“…These include a one-step correlated double-capture process [15,16] where the entrance channel crosses the DEC channels and a two-step transfer involving electron-electron interaction referred to as correlated transfer excitation [12,14,[16][17][18]. In addition, auto-transfer to Rydberg (ATR) [19][20][21] is also proposed. Via long-range coupling, it transfers a part of the population in symmetric states to the corresponding nearly degenerate Rydberg states on the way out of the collision.…”

Unexpected X-Ray Emission due to Formation of Bound Doubly Excited States

“…This effect has cre-ated controversial discussions as to whether it happens instantaneously, sequentially, or postcollisionally with flourishing activities resulting in subjects such as "autotransfer to Rydberg states," "correlated double capture," and "dielectronic excitation" [4][5][6][7].…”