THE CAGE EFFECT AND ENVIRONMENTAL ISOMERS IN LIQUIDS WITH SPECIAL EMPHASIS ON WATER

Environmental isomers are molecules of the same molecular species which are distinguishable because they exist in different liquid cages. A possible example are the two 'states'' of water which account for many of the water anomalies. This paper derives the conditions for distinguishability when the cages exist in dynamic equilibrium. The approach involves first a Fourier transform and then is analogous to interpreting the coalescence of spectral lines in dynamic magnetic resonance. The analogy exists because cage switching causes a frequency switching of the electronic-state Schroedinger wave of the caged molecule. The result is that the distinguishability of two cage environments (a and b) depends both on the potential energy difference \E(a) - E(b)\ of the caged molecule in the two environments and on the mean time tau for cage switching. Fluctuations in E(a)(b) due to random Brownian motions of molecules in the cage wall produce intrinsic widths that are similar to the natural line widths in NMR. Practical criteria for distinguishability are: (i) \E(a) - E(b)\ > 4 kJ/mol and (ii) 2pi\E(a) - E(b)\tau/hL > 5. The two states of water meet these criteria and thus can be environmental isomers.