The diffusion of helium through both H2O and D2O amorphous solid water (ASW) has been measured between 55K and 110K. We find the diffusion rate is dependent on the isotopic composition of the ASW lattice. This lattice isotope effect is the "inverse" of a normal isotope effect, in that diffusion is faster in the heavier (D2O) isotope. Transition state theory calculations show that the isotope effect is due to a tight transition state results in a large zero point vibrational energy differences at the transition state predominantly due to hindered rotations of water in the lattice.
Revised: July 13, 2011 |
Published: May 14, 2004
Citation
Daschbach J.L., G.K. Schenter, P. Ayotte, R.S. Smith, and B.D. Kay. 2004.Helium Diffusion Through H2O and D2O Amorphous Ice: A Lattice Inverse Istope Effect.Physical Review Letters 92, no. 19:Art. no. 198306.PNNL-SA-40138.