Normalized QMS ion counts for m/z = 19 (DHO), 15 (NH), and 29 (¹³CO) as functions of the temperature at the deposition pressure of P_d = 6 × 10⁻⁷ Torr. The three species are representative of H₂O, NH₃, and CO, respectively. The blue line represents the best fit using the relation Q = 1 - D. Red dots are the derivative of the column density expressed in monolayers (right vertical axes).