Photoemission and electron scattering in Cs3Bi and Cs3Sb

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Abstract
Photoemission studies of Cs3Bi and Cs3Sb have been made for the spectral region from 5 to 11.5 eV. Structure in the energy distribution as a result of structure in the valence‐band density of states is the same as that measured previously at lower energies. As the photon energy is increased, this structure moves to higher energy by an amount equal to the increase of h ν. This further supports the argument that conservation of k is an unimportant selection rule for these materials. Monte Carlo calculations of photoemission from these materials have made possible a determination of the scattering parameters and density of states. Photoemission from Cs3Sb can be understood quantitatively only by including scattering of electrons at acceptor sites. For both Cs3Sb and Cs3Bi, the higher lying valence‐band peak has an area twice that of the lower lying peak. However, the electron‐electron scattering cross section happens to increase with increasing electron energy so as to reduce the magnitude of the higher lying peak in the photoelectron energy distribution in a particular way; the higher energy peak is of smaller magnitude than the lower peak but has nearly the same relative height at all photon energies. This shows that one must be careful in interpreting structure in the energy distribution as a being a replica of the density of states.