Re-evaluation of the W value for electrons in dry air

Abstract

In 1979 ICRU recommended the value W=(33.85+or-0.05) eV for the average energy required for electrons to produce an ion pair in dry air. A re-evaluation is presented which is based on recently published stopping-power data. The new result is W/e=(33.97+or-0.05) JC-1, where all stated uncertainties are estimated standard deviations.