The total ionization produced by 25- to 50-keV H+, <tex-math>${\rm O}^{+}$</tex-math>, and Ar+ ions when stopped in CO2, C2 H4, and C2 H2 gases has been measured. The average energy required to produce an ion pair (W) has been obtained from these measurements and compared to alpha-particle and alpha-recoil results. Calculation for CO2 of the energy ultimately going into kinetic energy of gas atoms indicates that the competition between ionization and excitation remains roughly the same at keV energies as it is at MeV energies, but that for the heavy ions a large fraction of the initial energy goes into this kinetic energy of gas atoms.

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