Paper SS1-MoA8
The H/D Exchange in Water at Surfaces of Ice and on Cu(100) Studied by Infrared Vibrational Spectroscopy and DFT Calculations

Monday, October 15, 2007, 4:20 pm, Room 608

Proton transfer in water through the reaction H₂O + D₂O -> 2HDO is one of many intriguing properties of water. We have studied the exchange in water at ice surfaces and on a Cu(100) surface using infrared vibrational spectroscopy. Intact molecules of H₂O and D₂O are observed up on adsorption at 84 K and no H/D exchange is observed in H₂O/D₂O mixtures . By monitoring the O-H (3695 cm^-1) and O-D (2730 cm^-1) stretches assigned to none-hydrogen bonded water molecules at the surface of the ice we have followed the H/D exchange in the temperature region 84 - 145 K. A clear isotope effect is observed in 4/1 mixtures of H₂O/D₂O or D₂O/H₂O. The majority isotope governs the exchange efficiency. The exchange is completed at 140 K resulting in at total scrambling of the isotopes. The vibrational data is interpreted with the aide of DFT calculations of small water complexes.