Pseudolocal phonons in p-terphenyl : pentacene single crystals

The structural nature of the phonon sidebands in the fluorescence and excitation spectra of pentacene guests in p‐terphenyl crystals at 4.2 K are investigated using site‐selective spectroscopy. The distinct features in the phonon sideband structure were observed to depend significantly on the guest site configuration of pentacene occupying four inequivalent sites in the triclinic p‐terphenyl lattice. The sharp peaks dominating the phonon sideband structure are assumed to arise from the pseudolocal phonons. The eigenvalues and eigenvectors of the pseudolocal phonons are calculated carrying out a modified normal mode analysis on the distinct pentacene site configurations including the contribution of all intermolecular atom‐pair interactions.