Influence of temperature and pressure on narrow-band fluorescence of 1,8-diphenyloctatetraene in solid crystalline solutions

Forbidden 21Ag–11Ag fluorescence of 1,8-diphenyloctatetraene has been recorded in n-tetradecane and aromatic crystal hosts (naphthalene, bibenzyl, p-quaterphenyl) in the temperature interval from 5 to 50 K and under the He gas pressure up to 200 bar. Both the pressure and the temperature-induced shifts of lines have opposite signs in Shpolskii and aromatic matrices. The pressure and temperature shifts as well as the increase of S1–S0 one-photon transition probability in aromatic crystals were rationalised in terms of the change in S2–S1 splitting that is smaller in aromatic hosts as compared to n-alkanes.