A fluorescence model of the C[SUB]3[/SUB] radical in comets

The fluorescence spectrum of the C[SUB]3[/SUB] radical in comets is investigated. A theoretical model which takes into account the rotational structure and the different vibrational levels of the bending mode ν [SUB]2[/SUB] involved in the emision of the 4050 à \ group, is elaborated. This model is used to interpret high-resolution spectra of some recent comets. The agreement between observed and theoretical spectra is satisfactory with some realistic assumptions on the electronic oscillator strength and the dipole moment derivative, which determine the relative importance of the rotation-vibration transitions. Different synthetic spectra which show the influence of the Swings effect and the consequences of the change in the heliocentric distance are also calculated and are presented.