Field desorption point source of alkali and alkaline-earth metal ions

A field desorption point source of metal ions is explored. A continuous or pulse flux of Na, Cs and Ba ions from the W and Ir field emitter is achieved. The continuous flux of ions is realized when under certain conditions surface diffusion flux of adatoms to the apex of a tip is equal to desorption flux. The ion current was 0.001-0.1 nA. The ion current density in pulse (10 ns) amounted to 10/sup 3/ A/cm/sup 2/. Size of emission area can be changed from /spl sim/1 mcm to /spl sim/1 nm by varying conditions of desorption. The point source of metal ions can be used in ultra high vacuum installations.