Showing papers on "Water cluster published in 1970"

Water Cluster Ions: Rates of Formation and Decomposition of Hydrates of the Hydronium Ion

Abstract: The rates of formation of hydrates of H3O+ in the reactions H3O+(H2O)n−1+H2O+M⇆H3O+(H2O)n+M, n = 1, 2, 3, were studied using drift tube techniques. Experiments were performed at 337°K with mixtures of 0.5% to 1.8% partial pressure of water in argon at total pressures from 0.6 to 3.0 torr. Rate constants for the forward reactions decreased slowly with increasing E / P0 in the range 4–30 V cm−1·torr−1. Values for k1, k2, and k3 at 337°K were 6 × 10−28, 6 × 10−28, and 2 × 10−28 cm6/sec. Limits were estimated for the reverse reactions. Mobilities of the cluster sequence from H3O+ to H9O4+ were almost independent of E / P in the range studied, with zero‐field values of 3.0, 2.5, 2.2, and 2.0 cm2V−1·sec−1 in close agreement with the polarization‐limit Langevin theory.

A direct mass spectrometric study of the formation and reactions of water-cluster ions.

Abstract: : In an effort to establish the reasonableness of one postulate as to the origin of water-cluster ions in the D-region of the atmosphere, the authors have investigated the direct electron-impact ionization properties of small water clusters. Water clusters were generated in free-jet expansions of moist Argon, yielding an electron-impact mass-spectrum consisting of the ion series H(+).(H2O)n. Electron impact appearance potential measurements are described, yielding appearance potentials substantially higher than predicted from thermochemical cycles involving ion dissociation energies. Measurements were made of the cluster mass-spectrum as a function of extent of nucleation, of the variation of appearance potentials with extent of nucleation and of fragment-ion kinetic energies. Results of these measurements lead to the conclusion that not only do the larger water clusters fragment by loss of H2O as well as of OH, but that substantial excess internal and fragment kinetic energy is involved. The utility of ion peak-shape analysis in detecting fragmentation of Argon clusters is illustrated. (Author)