Solvated electrons in the upper atmosphere

Abstract

Solvated electrons have been postulated1–3 to exist in liquids and solids, and recent laboratory measurements4 have revealed that they exist even in the gas phase. In particular, these measurements suggest that eight water molecules are sufficient to bind an electron and give rise to a solvated electron of the kind (H2O)8−. This seems to be consistent with theoretical considerations5 suggesting that a dipole of molecular size must have a minimum dipole moment of about 2.5 D to support a bound state. According to theoretical calculations6, a cold, neutral water cluster (H2O)8 has a dipole moment of 4.61 D, so that larger (H2O)n clusters may be expected to bind an electron. Building on these ideas I consider here the possibility that solvated electrons may also exist in the Earth's upper atmosphere and that they may affect nucleation and aerosol formation. Furthermore, I suggest that upper-atmosphere solvated electrons may be detected, using rocket-borne ion mass spectrometers, and that they may be used as tracers for probing condensation nuclei.