Fast radiative cooling of anthracene: Dependence on internal energy

Fast radiative cooling of anthracene cations (C14H10)+ is studied with a compact electrostatic storage device, the Mini-Ring. The time evolution of the internal energy distribution of the stored ions is probed in a time range from 3 to 7 ms using laser-induced dissociation with 3.49-eV photons. The population decay rate due to radiative emission is measured to vary from 25 to 450s–1 as a function of the excitation energy in the range from 6 to 7.4 eV. After corrections of the infrared emission effect via vibrational transitions, the fluorescence emission rate due to electronic transitions from thermally excited electronic states is estimated and compared with a statistical molecular approach. In the considered internal energy range, the radiative cooling process is found to be dominated by the electronic transition, in good agreement with our previous work [S. Martin et al., Phys. Rev. Lett. 110, 063003 (2013)] focused on a narrower energy range.