über die optische Absorption von Schichten aus PbCl₂ und des Systems TlCl-KCl

Abstract

In the first part of this paper the optical absorption of amorphous films of PbCl₂, formed by quenching condensation, is shown and compared to the spectrum of PbCl₂ in its normal state. The sharp exciton band of crystalline PbCl₂ in the long wavelength region is considerably broadened in the spectrum of amorphous films. The transition from the amorphous state to the normal crystalline state is indicated by an abrupt, irreversible change in the absorption curve at 260‡ K. This comparatively high temperature of crystallisation seems to be due to the complicated structure of PbCl₂.

In the second part of this paper the optical absorption curves of evaporated films of the system TlCl-KCl are measured. A shift of the absorption bands as a function of the composition is found. The 3,46-eV-maximum of pure TlCl is coordinated to the A-band of the KCl∶Tl-phosphor. On the other hand there is no connection between the 5,82-eV-maximum of TlCl and the known bands of KCl∶Tl.