Structure in the Energy Distribution of Photoelectrons fromK3Sb andCs3Sb

The energy distributions of photoelectrons from ${\mathrm{K}}_3$Sb and ${\mathrm{Cs}}_3$Sb show structure that is similar in form to structure in the spectral dependence of the optical absorption. One may rationalize this empirical result by saying that both the photoelectric and optical effects arise from structure in the state density of the valence band. Assuming that the optical absorption involves transitions to the conduction band, a lower limit for the electron affinity of the crystal is 0.6 ev for ${\mathrm{K}}_3$Sb and 0.4 ev for ${\mathrm{Cs}}_3$Sb.