Bohr velocity

There is a widespread opinion that stopping of projectiles at velocities below the Bohr velocity is essentially quantal. The claim appears plausible for insulators to the extent that electron promotion may be an essential sink of energy. 

Further developments for slow ions included the application of the density functional theory (DFT) by Echenique et al. [31-33], which yields a more sophisticated (and also non-linear) treatment of many-body effects in dense media. This theory explains also the oscillatory behavior of the stopping powers in the range of low velocities (v < Vq, Vq being the Bohr velocity). But the question of extending the DFT calculations to intermediate or large velocities is still a complicated numerical problem. 

Fig, 8,3. Experimental curves of Andersen et al. [8.18, 8,19] (fully drawn) for the Bethe logarithm (L ), the Barkas factor (f-i) and the factor (L,) are shown for the targets Al, Cu, Ag, and Au as function of the projectile velocity measured relative to the Bohr velocity, v, and as function of the projectile energy per nucleon. The dashed curves show the Barkas term as given by Jackson and McCarthy [8,7] while the dot-dashed curve represents the so-called Bloch contribution to L, (eq. 8.7). From Andersen et al. [8.18]. 

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