Quantum Size Effect on the Excited State of HgI₂,PbI₂and BiI₃Clusters and Molecules in Zeolite LTA

The absorption spectra are reported for HgI 2 , PbI 2 and BiI 3 clusters and molecules incorporated into supercages of zeolite LTA at various loading densities. The spectra exhibit bands originating from a molecule to five molecular clusters of HgI 2 and PbI 2 , and from a monomer and a dimer of BiI 3 . The excitation energies are largely shifted to the higher energy side compared with the respective bulk exciton energies, and shift with decreasing the number of molecules, indicating the quantum size effect on the excitation energy. The blue shift decreases in the order of HgI 2 , PbI 2 and BiI 3 . The blue shift can be interpreted qualitatively in terms of the effective mass approximation, but quantitative analysis is beyond the framework of the effective mass approximation. The quantum size effect on the oscillator strength is also observed.