A Stopping Power Formula for Helium Ions
The empirical ratio of He to H stopping powers from Ziegler, Biersack, and Littmark  is compared with the Brandt-Kitagawa theory , trying various choices for the screening length ˄ and the fractional number of electrons on the projectile ion q. The best agreement is obtained when ˄ = <r> and q = 1 - exp[-vr/(Z1v0)] are chosen for hydrogenic helium ion. The stopping power ratios are furthermore corrected because the stopping power is not simply proportional to \(Z_1^2\) as assumed in Ziegler’s scaling. A formula, which interpolates between a Lindhard-Scharff-like formula at low velocities and the Bethe-Bloch expression of high velocities, is used to make this correction.
KeywordsEffective Charge Screen Length Heavy Target Empirical Ratio Target Atomic Number
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