The photofragmentation of anthracene cations under continuous irradiation by visible light is used asa tool to measure the radiative exchanges between the isolated species and its environment. The comparison of the experimental results with a numerical simulation allows an absolute determination of the oscillator strength of the whole set of absorption lines. Experimental evidence is given that, besides infrared vibrational emission, the contribution of electronic transitions has to be-accounted for in the evaluation of the cooling rate.