If it is assumed that the electron-hole substituents are in thermal equilibrium, then it can be said that the photoluminescence bandstructure also decays with an averaged time constant weighted with respect to its thermal occupation . In the case of internal conversion being the dominant mechanism, a three dimensional energy continuum therefore behaves similarly to trap states. In the case of a thin well with a single confined level, this is analogous to the rate of thermal ionisation within the two-level system . This can be cast as :