I honestly have not looked into this, but I have guessed. I was sitting in my Analytical Chemistry class today and I over heard about equilibria. Now we all should know this by now, and if you don't send me a message from one chemist to another I will be glad to explain this. Now my concern is when a Hydronium cation is in the middle and 3 water molecules hovering around it. can we say there will be tunneling in between the Hydronium and the waters?