2001 Volume 70 Issue 11 Pages 3424-3427
Reflection spectra of (C2H5NH3)2CdCl4 single crystals have been investigated in the range of 3-30 eV using synchrotron radiation. Two kinds of exciton bands with the splitting of the order of 0.1 eV, which is almost equal to the spin-orbit splitting of a Cl atom, are observed at 6.19 and 8.20 eV at 7 K. These bands are located at the energy positions close to the lowest exciton bands of CdCl2 and C2H5NH3Cl crystals, respectively. On rising the sample temperatures, the 8.20 eV band shows a discontinuous peak-shift of 0.1 eV around the temperature where a structural phase transition occurs, while such a result is not observed for the 6.19 eV band. The 6.19 eV band is assigned to the electronic transition from the Cl- 3p valence band to the lower Cd2+ 5s conduction band, and the 8.20 eV band to that from the Cl- 3p valence band to the upper NH3- s-like conduction band.
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