Coherence in electronically excited dimers. II. Theory and its relationship to exciton dynamics
A theory of microwave absorption in coherent or incoherent states of multidimensional crystals is developed. Application of the theory to the cluster states (dimer, trimer, tetramer,..., etc) of linear chain systems and its relationship to microwave band-to-band transitions in coherent Frenkel excitons provides a new way of studying coherence in the excited levels of molecular solids. A quantitative treatment of the influence of exciton-phonon coupling of spin dynamics in a two-level system (dimer) and the extension to a multilevel system (exciton) is given. The results show that zero-field electron spin resonance can directly measure the cross section of the scattering processes in the excited state and that the technique is applicable to other classes of solids. Moreover, the anisotropy and the magnitude of intermolecular interactions can be established from these experiments.
Additional Information© 1975 The American Physical Society. Received 19 August 1974. This work was supported in part by a grant from the National Science Foundation and in part by the Inorganic Materials Research Division of Lawrence Berekeley Laboratory under the auspices of the U.S. Atomic Energy Commission.
Published - ZEWprb75a.pdf