Triplet excitons in molecular pairs: Analytical investigation of electron spin resonance

For triplet excitons in pairs of differently oriented molecules ESR lineshape is investigated analytically using a microscopic model. The model hamilton takes into account the coherent tranfer of the exciton between the two molecules, the Zeeman and fine-structure energy and the interaction with phonons. The analytical expression for the line positions and linewidths are evaluated using values characteristic for triplet excitons in naphthalene pairs.