Fast Nuclear Spin Conversion in Water Clusters and Ices: A Matrix Isolation Study

Russell Sliter, Melissa Gish, and Andrey F. Vilesov 

Department of Chemistry, University of Southern California, Los Angeles, USA

ABSTRACT
Single water molecules have been isolated in solid Ar matrices at 4 K and studied by rovibrational spectroscopy using FTIR in the regions of the ν₁, ν₂, and ν₃ modes. Upon nuclear spin conversion at 4 K, essentially pure para-H₂O was prepared, followed by subsequent fast annealing generating ice particles. FTIR studies of the vapor above the condensed water upon annealing to T≥250 K indicate fast reconversion of nuclear spin to equilibrium conditions. Our results indicate that nuclear spin conversion is fast in water dimers and larger clusters, which preclude preparation of concentrated samples of para-H₂O, such as in ice or vapor.

*J. Phys. Chem. A 2011, 115, p.9682–9688