Theoretical investigation of the negative ionization of hydrogen particles on metal surfaces with low work function

This work addresses the negative ionization of hydrogen particles on low work function metal surfaces, which is an important process for the field of the surface plasma negative ion beams sources. We present the theoretical model for the computer calculation of the negative ionization probability which takes into account the component of atom/ion velocity, parallel to the surface. The calculated negative ionization probability of hydrogen quantitatively fits to the experimental data in the wide range of ion exit energies. The theoretical estimation shows, that for the low work function converter surfaces (φ ∼ 1.5 eV) the negative ionization probability of hydrogen can be enhanced up to 30% if the hydrogen has velocity component parallel to the surface ∼0.05 a.u. (∼60 eV). Therefore, the H- ion production rate can be increased for a negative ion source configuration that implements the oblique exit angle of hydrogen.