Collective relaxation processes in atoms, molecules and clusters

Abstract

Abstract. Electron correlation is an essential driver of a variety of relaxation processes in excited atomic and molecular systems. These are phenomena which often lead to autoionization typically involving two-electron transitions, such as the well-known Auger effect. However, electron correlation can give rise also to higherorder processes characterized by multi-electron transitions. Basic examples include simultaneous two-electron emission upon recombination of an inner-shell vacancy (double Auger decay) or collective decay of two holes with emission of a single electron. First reports of this class of processes date back to the 1960's, but their investigation intensified only recently with the advent of free-electron lasers. High fluxes of high-energy photons induce multiple excitation or ionization of a system on the femtosecond timescale and under such conditions the importance of multielectron processes increases significantly. We present an overview of experimental and theoretical works on selected multi-electron relaxation phenomena in systems of different complexity, going from double Auger decay in atoms and small molecules to collective interatomic autoionization processes in nanoscale samples.

Highly efficient double ionization of mixed alkali dimers by intermolecular Coulombic decay

“…In contrast, for SPDI near threshold, the branching ratio to single ionization is much less than 1% for atoms [28] and small molecules [29]. For DAD, the branching ratio to Auger decay is typically a few percent for atoms [30]. As such, one can conclude that dICD can even be the dominant process in weaklybound systems for cases where it is energetically allowed.…”

Interatomic and Intermolecular Coulombic Decay

“…It is also interesting to compare collective ICD processes detailed above, and the three-electron ICD 23 ( Section 5.1.8 ) to collective Auger processes in atoms and molecules, which were recently summarized. 515 …”

Bimolecular reactions of the dications and trications of atoms and small molecules in the gas-phase

“…[47][48][49][50] This study of the formation and decay of core-excited and core-ionized species has spawned a whole series of sophisticated coincidence experiments. [51] More generally, away from resonances and above the double ionization threshold, the probability for forming atomic dications is commonly of the order of a few percent with respect to that for forming a monocation. [52][53][54] Whereas, the yield of ions resulting from molecular double ionization (see below) is often markedly larger.…”

“…[98] The increasing sophistication of these multi-parameter coincidence experiments has now been extended to higher levels of ionization providing an elegant and informative probe of the formation and fate of multiply-charged species. [51] 4.…”