The mechanism for ion neutralization at metal surfaces via surface plasmon excitation was previously suggested. It was shown that this mechanism is of comparable probability as the other two well studied mechanisms, namely, Auger and resonance tunneling neutralizations. In the present work we study the probability of exciting a bulk rather than surface plasmon during the neutralization process. The calculations show that the neutralization rate depends exponentially on the ion distance from the surface. And it is found to be important at small distances from the surface. The theory is applied to the scattering of protons from aluminium surface. Comparison between the transition rate for bulk plamon-assisted and surface plasmon-assisted and surface plasmon-assisted ion neutralization shows that the transition rate is lower by two orders of magnitude in the case of bulk plasmon-assisted neutralization as was expected.
