Stopping power of gases for heavy ions

Pulse-height and time-of-flight methods have been used to measure the electronic stopping cross sections for projectiles of 12C, 16O, 19F, 23Na, 24Mg, and 27Al, slowing in helium, neon, argon, krypton, and xenon. The ion energies were in the range 185 keV less than or equal to E less than or equal to 2560 keV. A semiempirical calculation of the electronic stopping cross section for projectiles with atomic numbers between 6 and 13 passing through the inert gases has been performed using a modification of the Firsov model. Using Hartree-Slater-Fock orbitals, and summing over the losses for the individual charge states of the projectiles, good agreement has been obtained with the experimental data. The main features of the stopping cross section seen in the data, such as the Z1 oscillation and the variation of the velocity dependence on Z1 and Z2, are present in the calculation. The inclusion of a modified form of the Bethe-Bloch formula as an additional term allows the increase of the velocity dependence for projectile velocities above v0 to be reproduced in the calculation