Illustration of the main cooling processes balancing the radioactive decay heating at all ejecta depths in the reference model m20mix100vnimH9. We show each dominant cooling rate (stepping down from the rate having the largest peak value at any depth) normalized to the local heating rate. The term “NT” stands for non-thermal processes (in this context non-thermalexcitation and ionization) and “COL” stands for collisional processes (i.e., collisional excitation).