A flowing afterglow study of water vapour

A flowing afterglow system has been used to measure the gas-phase, thermal-energy rate constants for reactions between a variety of ions and water-vapour molecules at 300K. A method of measuring water-vapour flow-rates has been developed which may be readily extended to other vapours. Rate constants, together with reaction processes, are reported for the ions He+, Ne+, Ar+, Ar+2, N+, N+2, H2O+, C+, CO+ and O+ reacting with water vapour, together with measurements of the three-body rate constants for the systems O+2+ H2O + Ar and H3O++ H2O + He, and the Penning ionization cross-section for the He (23S)+ H2O system.