Fluorescence of deutero-chrome alum

Abstract

Fluorescence transitions between the 2 E excited state and the 4 A 2 ground state of Cr +++ in KAI (SO 4) 2·12D 2O:Cr +++ are observed while similar transitions do not occur in the corresponding protonated compound. This is taken as confirmation of the hypothesis that the excitation energy in the protonated compound is dissipated via radiationless processes through the OH vibrational overtones. In the case of OD, the transfer of energy from the electronic states is less efficient and hence radiative processes can occur. The temperature dependence of the fluorescence lifetime is given and evidence is presented for the lack of a center of symmetry for the trivalent cation in the low temperature form of this alum.