Some kinetic and thermochemical aspects of sodium in the stratosphere

Metallic species produced in the atmosphere by meteoroid ablation may play an important role in atmospheric chemistry, especially that related to ozone. Observations of sodium at 90 km yield estimated concentrations of 3 × 10³ cm^-3. We report here calculations on NaCl, which is formed by the reaction of NaOH with HCl. We show that while NaCl photolyzes rapidly in the upper stratosphere, in the 30-35 km region it rapidly polymerizes, producing (NaCl)_m, where m ≤ 10,000. One effect of this polymerization is to reduce the concentration of NaCl to 30 cm^-3 and subsequent polymers to even lower concentrations, where they can act as a permanent reservoir for sodium and chlorine and cease to affect ozone chemistry. These calculations represent upper limits for (NaCl)_m, since other metallic salts may copolymerize with NaCl.