TIME-CORRELATED ION FORMATION IN THE FIELD DESORPTION OF HYDROGEN

Time-correlated ion formation is observed in the field ion current of hydrogen from a tungsten emitter. The simultaneous emission of pairs of ions, where each pair contains two of the three possible ions H+, H2+, or H3+, is confirmed by auto- and cross-correlation measurements. From the observed dependence on field strength and hydrogen pressure and supplementary laser induced field desorption experiments we conclude that the time-correlated ion formation is due to electron stimulated field desorption (ESFD). The amount of correlated ions can reach approximately 16% of the total field ion rate for a hydrogen pressure of 10(-5) mbar.