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Optical absorption (~1–5 eV) in rf-deposited hydrogenated (20–40 at. %) amorphous “diamondlike” carbon films has been studied as a function of heat treatment. For E >~ 2.5 eV a Tauc behavior is exhibited. Optical band gaps Eg are E0, the width of the tail, is quantitatively explained in terms of the annealing temperature TH. Increasing TH (<700 >K) reduces the hydrogen content, lowers Eg, and appears to harden the films. Eg is determined to be a linear function of E0. Additional analysis was performed in terms of a divergence temperature, T0; the results of this analysis are comparable to those observed in a-Si:H.