Sodium hydroxide ions in the stratosphere

Abstract

Recently observed non‐proton hydrate ions observed at 37 km by Arnold, Böhringer and Henschen are interpreted as being protonated sodium hydroxide cluster ions of the form NaOH 2 + (H 2 O) n (NaOH) m . Values of n from 0 to 4 and m from 0 to 2 allow an interpretation of all seven unidentified NPH ions reported by Arnold et al . The sodium oxide molecules believed to exist below the well‐known sodium layer around 90 km are presumed to convert to the more stable NaOH molecules below ∼ 40 km where the OH/H and HO 2 /H concentration ratios become very large. The very large proton affinity of NaOH (∼248 kcal mol −1 ) virtually assures proton transfer from the H + (H 2 O) n ions that are produced in the stratosphere and observed to be dominant above ∼ 40 km. The possible role of other metallic species in stratospheric ion chemistry is briefly discussed.