This is a repository copy of Enhanced global primary production by biogenic aerosol via diffuse radiation fertilization.

The gas-phase reactions of a selection of sodium-containing species with atmospheric constituents, relevant to the chemistry of meteor-ablated Na in the upper atmosphere, were studied in a fast flow tube using multi-photon ionisation time-of-flight mass spectrometry.For the first time unambiguous observations of NaO and NaOH in the gas phase under atmospheric conditions have been achieved. This enabled the direct measurement of the rate constants for the reactions of NaO with H 2 , H 2 O and CO, and of NaOH with CO 2 , which at 300-310 K were found to be (at 2 confidence level): k(NaO + H 2 O) = (2.4 ± 0.6)  10 -10 cm 3 molecule -1 s -1 , k(NaO + H 2 ) = (4.9 ± 1.2)  10 -12 cm 3 molecule -1 s -1 , k(NaO + CO) = (9 ± 4)  10 -11 cm 3 molecule -1 s -1 , and k(NaOH + CO 2 + M) = (7.6 ± 1.6)  10 -29 cm 6 molecule -2 s -1 (P = 1 -4 Torr). The NaO + H 2 reaction was found to make NaOH with a branching ratio ≥ 99%. A combination of quantum chemistry and statistical rate theory calculations are used to interpret the reaction kinetics and extrapolate the atmospherically relevant experimental results to mesospheric temperatures and pressures. The NaO + H 2 O and NaOH + CO 2 reactions act sequentially to provide the major atmospheric sink of meteoric Na, and therefore have a significant impact on the underside of the Na layer in the terrestrial mesosphere: the newly determined rate constants shift the modelled peak to about 93 km, i.e. two km higher than observed by ground-based lidars. This highlights further uncertainties in the Na chemistry cycle such as the unknown rate constant of the NaOH + H reaction. The fast Narecycling reaction between NaO and CO and a re-evaluated rate constant of the NaO + CO 2 sink should be now considered in chemical models of the Martian Na layer.

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