Effects of High Pressures on the Phosphorescence of Aromatic Hydrocarbons

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Abstract
The phosphorescence spectra, intensities, and lifetimes have been measured for 10 aromatic hydrocarbons, dispersed in polymethylmethacrylate, in the 0–32‐kbar pressure range at 298°K. It is observed that the red shift is small (200–450 cm−1 at 32 kbar) and comparable to the red shift observed in fluorescence. The measured phosphorescence lifetime decreases monotonically with increasing pressures over the 0–32‐kbar range for nine of the ten aromatics. From dynamic intensity measurements at 0, 10, and 20 kbar pressure it is concluded that the natural lifetime decreases by ≲30% at 20 kbar. Also, the radiationless rate constant must increase by at least the same amount. It is concluded that pressure enhances spin—orbit interaction and the vibrational overlap factors.