STABILITY UNDER PRESSURE OF EXCIMERS OF ANTHRACENE-DERIVATIVES

Catastrophe theory has been applied to classify the properties of the potential surfaces of excimer states in some anthracene derivatives. The observed dependence of the excimer emission frequencies with pressure has been reproduced using as model for the excited state surface an anharmonic quartic potential modulated by pressure. A discussion is given in terms of "stable" and "unstable" systems on the basis of the deformation of the anharmonic Potential surface when pressure is changed. Unstable systems, like 9,10-dichloro- and 9,10-dibromo-anthracene, undergo pressure-induced phase transitions.