One can get a feel for the degree of molecular rigidity, and therefore a qualitative probing of cavity-type internal conversion within the system, by examining the combined Huang-Rhys factor (Equation ). A series of anthracene derivatives were examined by Tsai and co-workers , and it was found that each yielded different Y values and displayed similar photophysical properties, but with rate constants differing by more than an order of magnitude. Simply put, the size of Y correlates directly with the degree of wavefunction overlap. However, it should be emphasised that this is only the case for electrodynamic internal conversion, where the reverse is true for non-cavity based internal conversion, since greater overlap results directly stronger wavefunction overlap and therefore less vibronic coupling, as shown by Manian and co-workers . This does however, offer an interesting opportunity for cavity tuning, whereby electromagnetic fluctuations could be shifted to minimise internal conversion. Rather, even the most minute of cavity alterations can have drastic effects on the internal conversion mechanism.