W values of protons in liquid water.

The W values of protons in liquid water were calculated for energies from 0.1 keV to 10 MeV using the continuous slowing down approximation as well as three models for the calculation of the differential ionisation cross-sections of water for protons published in recent years. The W values determined by means of the three models differ only marginally from each other and lie between 25 and 26 eV at proton energies >5 MeV. This high-energy W value is approximately 3 eV lower than that in water vapour.