Publisher's Note: Threshold effect in the energy loss of slow protons and deuterons channeled in Au crystals [Phys. Rev. A75, 010901 (2007)]

Electronic Stopping Power in Gold: The Role ofdElectrons and theH/HeAnomaly

“…We find very good quantitative agreement with some recent low energy ion scattering experiments on thin gold films [2][3][4]. The results are analyzed in terms of the electronic excitations that are responsible for the energy loss, which very clearly shows why the slope of S e increases with projectile velocity.…”

“…1 shows our results for S e (v) for H and He projectiles in gold for the velocity range v = 0.06−0.50 a.u. We also plot results of some recent experiments performed on thin single crystal gold films oriented along 100 [2] and polycrystalline gold films [3,4]. The agreement between our simulations and the experiments is noticeable.…”

“…Experiments on noble metals Cu, Ag and Au, show pronounced nonlinearities in S e (v) [2-4, 8, 11, 15, 19]. In the case of slow H and He ions in gold [2][3][4], S e (v) displays an increase in the slope roughly around v 0.18 a.u. This is usually attributed to a threshold projectile velocity needed to excite the d-band electrons that are relatively tightly bound.…”

“…Substantial progress has been made for weakly non-adiabatic problems such as the chemistry of vibrationally excited molecules landing on metal surfaces [1], but not in the stronger coupling regime of radiation damage. Recently, the electronic stopping power for swift ions in gold has been carefully characterized by experiments [2][3][4], showing flagrant discrepancies with the established paradigm for such problems [5,6], and only qualitative agreement with time-dependent tight-binding studies [7], and with detailed studies for protons based on first principles [8], leaving very fundamental questions unanswered in spite of the apparent simplicity of the system. Most notably the H/He anomaly: the present understanding predicts a stopping power for H higher than for He at low velocities [6], which strongly contradicts the recent experiments [4].…”

“…It seems a plausible explanation that at low projectile velocity only s-band electrons from the states around the Fermi energy contribute to the stopping and at higher velocity electrons in the d band that lie relatively deeper in energy are also able to take part in it, resulting in an increase in the slope of S e . Thus, comparisons have been made [2,4] with jellium using the average electron density n e of the s electrons (r s = 3.01 a.u., where n −1 e = 4 3 πr 3 s ), using r s = 1.49 a.u., corresponding to an effective number of s and d electrons [4], or of the density in the 100 channel (r s = 1.8 a.u.). However, the jellium predictions do not agree with the experimental results except at projectile velocities around v = 0.6 a.u.…”