Robinson & Frosch discuss internal conversions in terms of nonstationary states. Internal conversion can be reimagined discussed as the problem of energy transfer in the solid state; while the initial and final state may not be in resonance, a rigorous but reasonable model whereby the set of final states is constructed using simple mathematical properties can be used to liken the problem to small lattice vibrations. A series of assumptions can be made here: firstly environmental effects (eg. solvent) have no influence on the electronic coupling and a weak influence on the vibronic coupling through Franck-Condon factors, and that each vibration, in the zeroth-order, is near-degenerate and coupled to the 0-band. From here, the combination of each individual state will form a discrete band, with a width ℵ proportional to the occupational vibrational quanta (typically ∼1 cm -1 ). Importantly, as more vibrations contribute to the overall rate, those states closer to resonance make a more measurable contribution to the rate. Thus, over small timescales, the transition probability can be cast in terms of either near or far resonance :