Beyond solvation of HX acids at the ice surface: Kinetics of H-bond chemistry of ice and acid-hydrate nanoparticles

COLL 347

J.P. Devlin, Department of Chemistry, Oklahoma State University, Stillwater, OK 74078 and V. Buch, Fritz Haber Institute for Molecular Dynamics, Hebrew University, 91904 Jerusalem, Israel.
After a brief review of the behavior of submonolayer quantities of HCl and HBr on the surface of ice nanocrystals in the 50 – 100 K range, attention will be directed to the kinetics and mechanisms for the conversion of ice nanocrystals to acid-hydrate particles in the 110 – 150 K range. With an abundance of acid at particle surfaces, ice particles convert to the monohydrate (HCl) or dihydrate (HBr) with a rate determined by diffusion through the hydrate crust that quickly surrounds the ice particle cores. This rate control factor is apparent from a ~t(exp 1/3) dependence of the rate plus the results of application of the shrinking-core model of particle reaction. The kinetics of the repetitive cyclic inter-conversion of mono- and dihydrate crystalline particles will also be examined. The results of a Monte Carlo particle-reaction model developed by V. Buch and C. Yinnon will be applied to the data.