Structured Luminescence Emission in Cadmium Sulphide at 2.0 to 2.8 μm

For cadmium sulphide a new structured luminescence emission in the wavelength region 2.0 to 2.8 μm and the corresponding excitation spectra are reported. The luminescence is believed to occur at an acceptor centre analogous to that responsible for the 1.5 to 2.2 μm banded emission. Cadmium sulphide phosphors which exhibit luminescence between 2.0 and 2.8 μm also show an apparent shift of the well‐known 1.06 μm emission band to shorter wavelengths, the shift is caused by the existence of a new luminescence emission band with an intensity maximum at 0.90 μm. By considering the new acceptor centre and a common donor level the 0.90 μm luminescence emission band may be explained on the same donor‐acceptor pair model previously proposed to explain the origin of the 1.06 μm luminescence emission band. Comparision of absorption and emission transitions for the two luminescence centres on the model proposed to explain the 1.06 μm and 1.5 to 2.2 μm emission bands leads to a consistent value of approximately 0.2 eV for the energy separation of the two acceptor levels.