Spin selectivity of H₂O isomers in vapors above boiling water demonstrates more than 5:1 ortho-/para-ratio

A spin selectivity of processes occurring in vapor above the surface of boiling water has been detected for the first time, to the best of our knowledge. A tunable diode laser operated at 1.35 microns was used to analyze the relative content of Н₂О spin isomers in water vapor. A significant increase in the H₂O ortho-/para-molecule ratio (5:1) compared to the statistically stable state (3:1) was observed at 80-90°C. A possible mechanism of the phenomenon could be associated with the depletion of vapor by the para-H₂O isomer due to its higher activity in condensation and formation of water microdrops.