A time-resolved electron spin resonance study of mobile excited triplet states in the anthracene-1,2,4,5-tetracyanobenzene crystal

Abstract

Mobile triplet excitations (excitons) in the antracene-1,2,4,5-tetracyanobenzene crystal are studied by analysis the e.s.r. transient nutation signals after laser pulse excitation. Values of the relaxation times T₁ and T₂ are measured as a function of the temperature and of the crystal orientation. Their values are discussed in terms of the time modulation of the fine tensor caused by the exciton and the lattice motion. In the phase stable at low temperature the crystal structure consists of magnetically inequivalent stacks of anthracene and tetracyanobenzene molecules and a detailed analysis of the variation of T₂^–1 with the crystal orientation gives an estimate of the interaction between anthracene molecules in adjacent stacks.