In the case of a dimer, excitons could not only decay to the ground state while conserving spin, but also spontaneously transfer to the coupled fragment. In this picture, transfer could be mediated through contributions from a spin-orbit coupling term in the transfer matrix. Martynov and co-workers found that Plotnikov's model (Equation ) was able to capture the internal conversion behaviour in a series of Tetrathiafulvalene chromophores at varying temperatures (Figure ), capturing physical effects that would be expected within Kasha's exciton model . Specifically, splitting of the energy levels, with each split corresponding to a Frenkel exciton residing on a single molecular fragment, would be expected to result in favourable pathways from one fragment compared to the other. Interestingly, temperature effects were minimal if not negligible, with the largest shift between 100 and 500 Kelvin of ∼6%.