Direct and indirect probing of recurrent fluorescence on carbon-bearing molecules, metal clusters and sulfur allotropes

The radiative decay pathway of recurrent fluorescence has in the last decade been recognized as an efficient cooling mechanism in many carbon-bearing molecules and metal clusters in isolated conditions. Experiments have demonstrated that many of these systems radiate at surprisingly high rates, often with a distinct dependence on the precise size of the particles. There are several consequences of an active radiative cooling channel, as for example in the production of size-selected particles in an evaporative ensemble, where abundances of highly radiating sizes will be enriched. In an astrochemical context, recurrent fluorescence provides an efficient pathway to dissipate internal energy in photo-dominated regions of the interstellar medium. Despite its relevance, there are several open questions about the fundamental mechanism responsible for recurrent fluorescence, involving the population of electronic states via inverse internal conversion. In this talk, I will provide a general overview of the history of the study of recurrent fluorescence using ion traps and storage rings, as well as the knowns and unknows about the process, focusing on future studies using novel spectroscopic techniques.