Secondary electron emission from lunar soil: Yields, energy distributions, and charging effects

We report the electron emission and charging of sub-mature lunar highland soil 61241 by electron impact under ultra-high vacuum for 40–2000 eV electrons. The energy distribution of emitted secondary electrons was measured as a function of primary electron energy under neutral charging conditions, and electron energy loss spectroscopy was used to determine the ∼8 eV band gap. Total electron yields were obtained with low electron fluxes. Imaging the soil with a Scanning Auger Microprobe using 10 keV electrons revealed differential grain motion induced by charging in ultra-high vacuum.