Reflectivity and Electronic Structures of Layered Ionic Crystals, (C_<i>n</i>H_2<i>n</i>+1NH₃)₂CdCl₄:<i>n</i>=1, 2, 3

Abstract

The reflection spectra of (C n H 2 n +1 NH 3 ) 2 CdCl 4 were measured in the photon energy region of 0.5–25 eV at room temperature (RT) and liquid nitrogen temperature (LNT) by means of synchrotron radiation. It was found that absorption spectra of the present crystals resemble that of CdCl 2 crystals except for an additional peak at 5.10 eV (RT). The energy of the additional peak shifts with temperature by as much as 0.38 eV from 5.10 eV (RT) to 5.48 eV (LNT). This absorption peak has doublet structure and the splitting energy is 0.1 eV, which is the same magnitude as the spinorbit splitting of a chlorine atom. The band is assigned to be an electronic transition from the chlorine 3 p valence band to a new-type conduction band which is composed of alkylammonium bases and is below the ordinary Cd 5 s conduction band in energy.