Energy Required to Produce One Ion Pair for Several Gases

The absolute values of $W$, the energy required to produce one ion pair, for electrons have been determined for several gases. A parallel plate extrapolation ionization chamber in conjunction with a ferrous sulfate dosimeter was used. The gases investigated were air, nitrogen, oxygen, carbon dioxide, argon, methane, and ethylene; and the absolute values of $W$ were 33.9, 34.8, 30.9, 32.6, 25.5, 26.8, and 26.3 ev, respectively.