Since the ensembles of nuclei and photons only interact through the electromagnetic force, whose carrier particle is the photon, such a definition naturally considers all interactions, including collisions, to be mitigated by photons and I call these transitions from now on thermal transitions. Consequently, the first law of thermodynamics is automatically fulfilled. In the next step, I investigate the rate of such transitions using Markov chains before combining it with transitions mitigated by transition events.