Normalized m/z = 4 ion current after background substraction (equivalent to the normalized D₂ flux) during three experiments performed at ~140 K (left panel), ~130 K (middle panel), and ~120 K (right panel) on a 3.4 μm thick a-C:D analog. Black solid lines correspond to the normalized D₂ flux during irradiation (irradiation starts at t = 0), while colored solid lines correspond to 1 – normalized D₂ flux after irradiation (irradiation stops at t = 0).