Solvated electrons in the upper atmosphere

Abstract

Solvated electrons have been postulated^1–3 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.