Calculation of neutral fraction for ion neutralization at metal surfaces by bulk-plasmon excitation

The excitation of bulk plasmons during the neutralization of protons scattered from metal surfaces was analyzed theoretically in previous work. Also, experimental evidence for this mechanism is now discussed in the literature. In this work the neutral fraction generated by this mechanism is calculated. The calculation for the neutral fraction in the scattering of protons from aluminum surface shows that it is quite small compared to that for surface-plasmon-assisted neutralization. The characteristic velocity for bulk-plasmons-assisted neutralization is 0.0009 (in atomic units). Its value for surface-plasmon-assisted neutralization is 0.75. It is concluded that, within the assumption of our theory that there is no penetration of protons into the surface (implying low-energy protons), the mechanism of surface-plasmons-assisted neutralization would be expected to be more important than that of bulk-plasmon-assisted neutralization.