Abstract
The surface of the Moon is covered by a layer of dust grains. On the sunlit side, the photoemission dominates other charging processes and the work function of grains determines the maximum energy of the originated photoelectrons and, consequently, the grain surface potential.
We present laboratory measurements of the work function on a single micrometer-sized lunar dust simulant captured in an electrodynamic trap and irradiated by UV photons. The first results indicate that the work function of lunar dust simulant Minnesota Lunar Simulant grains exceeds 5 eV.
We suggest that a slight difference between the work functions determined for two grains is probably caused by the shape effect. The photoelectron yield in the energy range of about 20 eV (58 nm) estimated from the measurements is around 0.05 and it is in good agreement with the previous results.