CO ice desorption during warmup for two different deposition temperatures, 7 K (thick solid trace) and 20 K (thick dotted trace). The desorption of H₂ in the samples deposited at 7 K (thin solid trace) and 20 K (thin dotted trace) are also shown. The ion current (A) is plotted on a logarithmic scale, for a better appreciation of the curve profile, and roughly corresponds to partial pressure in mbar.