Zeeman effect in complex molecules in solid solutions with laser T1 → S0 excitation. New possibilities for investigation of spin—lattice relaxation

The main peculiarities of Zeeman-effect in phosphorescence spectra of randomly oriented molecular systems under selective T₁→S₀ excitation are investigated. On this basis a new method of measuring triplet state characteristics and spin—lattice relaxation rates in solid solutions is proposed. The results of Zeeman-effect investigations on 5-bromo-acenaphtene in ethanol and butylbromide at magnetic fields 10–50 kG at helium temperatures are given as an example. At low fields the deviation from Boltzmann equilibrium in the spin system of the molecule is observed and the rates of spin—lattice relaxation are determined.