RAMAN PHONON-SPECTRA AND LATTICE-DYNAMICS OF 7-METHOXYCOUMARIN UNDER PRESSURE

Raman phonon spectra of 7-methoxycoumarin in the lattice phonon region have been measured in the range 0-5 GPa. A model atom-atom Buckingham potential has been determined to calculate structural parameters and Raman-active lattice phonons at ambient conditions and under pressure up to 14 GPa. The agreement with experiment is satisfactory. Results a re discussed with reference to the mechanism of the non-topochemical p hotodimerization which is confirmed to occur via defect sites of the c rystal rather than as a phonon-assisted process.