Stark effect is calculated by the perturbation theory method separately for the ortho and para water molecules. At room temperature, a 30%-difference in the energy change is found for the two species put in electric field. This implies a sorting of the ortho and para water molecules in non-uniform electric fields. The ortho/para water separation is suggested to occur in the course of steam sorption on a solid surface and of large-scale atmospheric processes.
@article{arxiv.physics/0703038,
title = {Ortho and Para Molecules of Water in Electric Field},
author = {S. N. Andreev and V. P. Makarov and V. I. Tikhonov and A. A. Volkov},
journal= {arXiv preprint arXiv:physics/0703038},
year = {2007}
}