Attenuation lengths of low-energy electrons in solids: The case of CoO

The effective attenuation length (EAL) of low-energy electrons in CoO is investigated by photoemission spectroscopy experiments (5 <= hv < 19eV) by measuring the Ag Fermi-edge signal through a CoO overlayer of increasing thickness. The EAL is found to increase when lowering the electron energy, but the experimental values are much smaller than expected from the commonly used Seah-Dench formulas [Surf. Interface Anal. 1, 2 (1979)].