Bond rearrangement caused by sudden multiple ionization of water molecules

Matt Leonard, A. Max Sayler, Mark A. Smith , Jiangfan Xia, Pengqian Wang, Kevin D. Carnes, Itzik Ben-Itzhak
(Kansas State University)

Bond rearrangement, namely the dissociation of water into H_2^+ + O^q+ following sudden ionization by swift highly charged ion impact, was investigated. Single ionization by fast proton impact exhibits a strong isotopic effect, the dissociation of H_2O^+ \to H_2^+ + O being about twice as likely as D_2O^+ \to D_2^+ + O, with HDO^+ \to HD^+ + O in between. This suggests that the bond-rearrangement does not happen during the slow dissociation, but rather during the very fast ionization, and thus H_2^+ should also be produced when the water molecule is multiply ionized. We observed that the H_2^+ + O^+ and H_2^+ + O^2+ production in 1 MeV/amu F^7+ + H_2O collisions are 0.209\pm 0.006% and 0.0665\pm 0.003%, respectively, of the main double-ionization dissociation product, H_2O^2+ \quad \to H^+ + OH^+. Similar dissociation channels in the heavier water isotopes, expected to be smaller, are under study.

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division,
Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Submitted to DAMOP, May 2004 in Tucson, AZ.