Stopping power of protons and alpha particles in H/sub 2/, He, N/sub 2/, O/sub 2/, CH/sub 4/, and air

Recent developments in the theory of the energy loss of charged particles in the gases H/sub 2/, He, N/sub 2/, O/sub 2/, and CH/sub 4/, permit a calculation of the stopping power with only one free parameter, : that needed in the description of the cubic correction term for the projectile charge. Experimental data for the stopping power of these gases for protons and alpha particles have been compared with calculated values. Once a value of the free parameter is assumed, it appears that no further improvements in the theory are required to explain the data for projectile energies above 0.5 MeV/u. The error of the theory is probably about +- 2% for these energies.