Unravelling the electronic nature of the radiative cooling of cobalt clusters

Abstract

In this paper, we report on the experimental determination of photon emission rates of laser-excited cobalt clusters, Con+ (n=5-23), deduced from fragmentation mass spectrometry and metastable decay fractions. The rates are so high that they can only be ascribed to recurrent fluorescence (RF), a process where emitting states are populated by inverse internal conversion, followed by photon emission. Cooling via electronic states is confirmed by quantitative agreement with calculated rates using the low-lying electronic transitions predicted by time-dependent density functional theory calculations for n=5-10, which are performed considering all electrons and including relativistic effects implicitly. The outstanding agreement between experiment and theory provides clear evidence that the clusters radiate via electronic states, being a consistent theoretical and experimental study invoking RF.