Conclusion
The characteristics of the LIF spectrum and the fluorescence lifetimes measured for the jet-cooled DPBBTD molecules are reported.
Since the vibronic progressions indicate harmonic, torsional vibrations, the potential energy curves along the torsional coordinate of the phenyl groups in DPBBTD in the S1 states are expected to have a single minimum at the coplanar conformation.
No indication of nonradiative processes from the S1 state was observed in the present study.
The fluorescence quantum yields are therefore expected to be unity and also the energy level of the S1 state should be lower than the level of the triplet state Tn state, which has the most effective interaction with the S1 state.
