The interaction of HCl with water‐ice at tropospheric temperatures

The uptake of HCl on frozen film ice surfaces was studied as a function of temperature and HCl partial pressure ( P HCl ) in a flow reactor. The temperatures ranged from 205 to 230 K, and P HCl was (0.4–2.0) × 10 −6 Torr. The initial uptake coefficients, γ, and the HCl surface coverage are reported. It was observed that the coverage varied from 3.0 × 10 14 molecules/cm² at 205 K to 1.0 × 10 14 molecules/cm² at 230 K. At 205 K the coverage showed no dependence on P HCl ; the average surface coverage was ∼ (2.0±0.7) ×10 14 molecules/cm² at saturation. This value is consistent with other studies on similarly prepared ice films. It was found that γ ∼0.1 at 205 K, but decreased substantially when the temperature increased; however, γ was insensitive to P HCl .