  Electron-stimulated desorption (ESD) of cryosorbed molecules on surfaces is a
process of relevance to fields as varied as vacuum dynamics in accelerators and
astrochemistry. While desorption from such molecular systems induced by keV
electrons and fast ions has been extensively studied, the sub-keV electron
regime is comparatively little known. We measured and quantified
electron-stimulated desorption from molecular ice systems (layers of N$_2$, CO,
CO$_2$, Ar and H$_2$O/D$_2$O condensed at cryogenic temperatures) in the
150-2000 eV electron energy range. In this regime stopping power is no longer
sufficient to explain the electron energy dependence of ESD yields. We
introduce the notion of desorption-relevant depth, which characterizes the
transition between two energy deposition regimes near the surface. We then
apply this notion to the different systems, showing how ESD in the sub-keV
regime can for example reveal the differences in species diffusion in
crystalline and porous amorphous CO$_2$ ices.
