Abstract
The fluorescence excitation and dispersed fluorescence spectra of jet-cooled o- and
m-toluidine were observed. Vibrational analysis of the spectra provided us with the
potentials for the internal rotation of the CH3 group in both ground and excited states. In
o-toluidine, a large potential barrier to the internal rotation in the ground state is
practically removed in the excited state. On the other hand, a nearly free internal
rotation of the CH3 group in the ground state of m-toluidine gains a large barrier by the
electronic excitation. The great change in the barrier height upon the electronic excitation is more remarkable than that found for fluorotoluene. A close relationship between the barrier height and the