Fundamental optical absorption of Cs4PbCl6

The fundamental absorption spectrum of Cs4PbCl6 has been observed for the first time. The spectrum exhibits novel structures. They are explained in terms of Pb2+-ion excitation of the octahedral Pb2+(Cl−)6 quasi-complexes, like the case of isolated Pb2+ ions, doped in fcc alkali halides. The individual quasi-complexes behave like quantum dots. The Cs4PbCl6 crystal provides the regular array of the quantum dots.