Column densities of H₂S and H₂S₂ in the ice during H-atom bombadrment. Upper panel: variation in H₂S₂ column density during H-atom exposure of an H₂S ice at 10 K. Lower panel: variation in H₂S column density as a function of H-atom fluence during bombardment of an H₂S ice at 10 K. The two-term exponential fitting to the points is shown in red, while the fast and slow components of the fitting are plotted in blue and green, respectively.