TEMPERATURE EFFECT OF ION MOLECULE REACTIONS IN A WATER MOLECULAR-BEAM CROSSED BY AN ELECTRON-BEAM

An effusive water molecular beam emitted by a cylindrical capillary was ionized by a transverse electron beam (energy 100 eV) just above the capillary outlet. This system was an open ion source of a cycloidal mass spectrometer. The temperature of the effusion capillary was varied from 343-873 K, and the pressure of the molecular beam from 0-0.5 Pa. Primary ionization processes and ion/molecule reactions were recorded directly, free from the effects of walls and slots which are characteristic of conventional systems used for investigating ionization processes. Secondary H3O+ ion production as a function of temperature and pressure of a water beam was examined.