Abstract The dynamics of several thermal and photochemical reactions in the solid-state are investigated by laser Raman spectroscopy, electronic spectroscopy and a rigid-body motion analysis of the thermal parameters of x-ray diffraction studies. Raman phonon spectroscopy along with electronic emission spectroscopy is used to identify the reaction mechanism. The possibility of occurence of any lattice and/or molecular intermediate is examined, by Raman spectroscopy of both phonons and intramolecular vibrations. The new concept of phonon-assisted reaction is tested by examining the role of an overdamped oscillation in a thermal reaction and that of a strong electron-phonon coupling in a photochemical reaction.