Photoemission from CsI: Calculation

Photoemission spectra were calculated for CsI based on crystal-momentum-conserving transitions between Bloch electron states. The energy bands of CsI were interpolated between levels at Γ and X obtained from calculations by Onodera. A fully relativistic tight-binding approximation and a pseudopotential fit were used for the valence and conduction bands, respectively. Weakly coupled Cs+ 5d conduction bands were not included in the calculation. Photoelectron distributions, generated by a computer sampling of the bands at 2600 points in the zone, agree reasonably well with experiment. The agreement confirms the interpretation of photoemission from CsI in terms of optical excitation between Bloch-wave states. © 1973 The American Physical Society.