Absence of energy loss in positron emission from metal surfaces

Creation of a monoenergetic pulsed positron beam

“…At present this is accomplished most effectively using a solid-state moderating material. 1,[6][7][8] In general, positrons emerge from the moderator with an energy of several electron Volts and an energy spread in the range 0.3-2 eV, although methods have been described to reduce this energy spread by as much as an order of magnitude in some instances. 9, 10 We have previously developed positron storage and handling techniques, using a Penning trap as a reservoir of thermalized, room-temperature positrons.…”

Disordered state of adsorbed hydrogens on Ni(111) surface studied by slow‐positron beam

“…β is a coefficient that takes account of internal reflection at the surface. Since the positron work function is around −1.3 eV in Ni, [13] thermalized positrons, which diffuse back to the surface, are emitted from the surface to vacuum as reemitted slow positrons. On all low-index Ni surfaces, H adsorbs dissociatively.…”

Behavior of the reemitted slow positron on hydrogen-adsorbed Ni (111) surface

“…Since the positron work function is $À1.3 eV in Ni [16], thermalized positrons, which diffuse back to the surface, are emitted from the surface to vacuum as reemitted slow positrons. Table 1 shows average counts/20 min of reemitted slow positrons emitted from the Ni (1 1 1) surface of hydrogen exposures 2.6 L, 3.0 L, 3.6 L and hydrogen exposures 4.5 L, 6.0 L, 6.9 L. In the present experiment, the sample voltage is 35 V and the positron beam of incident energy 1.97 keV is injected into the sample.…”