Zero-phonon transitions and vibronic coupling in the 1:1 charge-transfer crystal anthracene-pyromellitic-acid-dianhydride

High resolution spectra of the 1:1 CT-crystal anthracene-pyromellitic-acid-dianhydride (A-PMDA) show at low temperatures sharp structures in absorption and in emission. We attribute these structures to a zero-phonon transition which is accompanied by vibronic satellites. The spectra yield the coupling strength of the CT-transition to the phonons and to the vibrational modes of both the donor and acceptor molecule. © 1974.