Chemical desorption curves for H₂S as a function of H-atom fluence. Upper panel: estimated contribution from chemical desorption to the decrease in N(H₂S) as a function of fluence. The simple exponential fitting to the points is shown in red, and the linear fitting to the first 55 min of bombardment is shown in blue (dashed line). Lower panel: integrated intensity of the m/z = 34 signal measured by the QMS as a function of H-atom fluence during the same experiment. The red line shows the exponential fitting to the points.