Theory of ion neutralization at metal surfaces by surface plasmon excitation

A new mechanism is proposed for electron capture by ions scattered from metal surfaces, wherein a surface plasmon is excited during the capture process. The matrix element for this process and resultant neutral fraction are calculated for a simple model of electron capture to the hydrogen 1s state by a low-energy (few keV) proton incident on jellium. It is found that the transition rate for this capture channel is competitive with those for the previously-considered resonance tunneling and Auger channels. The calculation uses a novel second-quantization representation wherein terms equivalent to orthogonalization of the continuum metal and bound atomic wave functions arise naturally from a canonical transformation. These orthogonalization corrections are found to be important, suggesting that their omission is some previous resonance tunneling and Auger calculations may not be justified.