The low energy end of the S0→T1 absorption spectrum has been measured in anthracene and pyrene crystals from 220 to 330°K. A transition is found in both of these systems at an energy approximately 400 cm-1 below the 0-0 energy. The temperature dependence of this absorption reveals it to be excitation of a hot vibrational level of the ground state. Polarized excitation measurements have been carried out on the hot band absorption in anthracene, and it is found that the polarization ratio between light polarized parallel and perpendicular to the 6 axis is the same as that for the 0-0 transition. In addition it is found that there is no measurable shift (within 4 cm-1) in the position of the hot band maxima for the two polarizations. Within the framework of strong and weak coupling and the Born-Oppenheimer approximation only weak coupling is found to fit all the experimental facts.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry