Analysis of phonon structure in line-narrowed optical spectra

The complexities involved in interpretation of the phonon structure in hole burned (HB) and fluorescence line narrowed (FLN) spectra are discussed by analyzing the four contributions to the spectra, one of which is the zero-phonon hole (line) and the remaining three due to multi-phonon transitions. It is concluded that HB spectra allow for a more reliable qualitative assessment of the electron–phonon coupling. In addition, related HB experiments provide good first estimates of the Huang–Rhys factor S, the mean phonon frequency ωm and Γinh. An application is given for the LHC II chlorophyll a/b antenna complex of photosystem II.