Laboratory measurements of the Mesosphere

The only metal species that can be observed directly in the mesosphere are the atomic neutrals and ions. Knowledge of the chemistry that controls the metal layers and the nature of the metal containing reservoir species has had to come from a combination of laboratory studies and modelling. Up until the 1980s, laboratory measurements of the rate coefficients for reactions involving metallic species were only available for ion-molecule reactions, which were studied in ion drift tubes. Since then, however, the two classical techniques of flash photolysis and the fast flow tube have been applied with great success to the challenging task of studying reactions of neutral metallic species in the gas phase, at the low temperatures characteristic of the upper atmosphere. The development of theoretical formalisms (ab initio quantum chemistry methods and statistical theory of reaction rates) has enabled insighful interpretation of the experimental data. Our group has made a substantial contribution to a growing database on the pertinent photochemistry of sodium, iron, magnesium, calcium, potassium and silicon neutral and ionic gas phase species. We have also conducted laboratory research on the synthesys of comic dust analogues, the nucleation and growth of meteor smoke particles and on mesospheric and stratospheric heterogeneous chemistry.