Inverse internal conversion in C below the electron detachment threshold

Inverse internal conversion followed by recurrent fluorescence was observed as a fast decay (10 μs range) in the time profile of neutral yields from photo-excited C 4 − molecular ions. We also elucidated the contribution of such electronic radiative cooling to the C 4 − ions with internal energy far below the detachment threshold by an alternative novel approach, observing the laser wavelength and storage time dependence (ms range) of the total yield of the photo-induced neutrals. Inverse internal conversion below the electron detachment threshold drives fast the radiative cooling of vibrationally hot C 4 − isolated in a vacuum.