Fluorescence Spectra of Several Aromatic Crystals under High Pressures

Abstract

The fluorescence spectra of crystalline chrysene, 1,2-benzanthracene, anthracene, and four derivatives of anthracene were surveyed in the 0–25-kbar pressure range. In addition to stronger reabsorption of the crystal fluorescence upon compression, a pressure exceeding 10 kbar results in significant modifications of the spectrum. Diffuse bands at longer wavelengths appear at the higher pressures and may be attributed to a reorientation of the molecules in the lattice and the creation of many defects, which favors excimer interaction. The effect is largest for anthracene, where the initial intensity distribution at 1 atm generally does not return after high pressures have been applied. The results appear to depend significantly upon the crystal size and preparation.