Spectrophotometric Studies of Holmium(III) Chloride-Aluminum(III) Chloride Vapor Complexes

摘要

The gas complexation reactions between LnCl sub 3 and Al sub 2 Cl sub 6 to yield molecular species of the form LnCl sub 3 (Al sub 2 Cl sub 6 )/sub x/ have been studied for a number of years. The spectrophotometric technique has been used to deduce the thermodynamic properties of the molecular species. We have studied the HoCl sub 3 (Al sub 2 Cl sub 6 )/sub x/ system from 600 to 900 exp 0 K and at Al sub 2 Cl sub 6 pressures between 1 and 7 atm. The Ho exp 3+ hypersensitive transition between exp 5 I sub 8 and exp 5 G sub 6 at 456 nm has been used to measure the complex vapor densities as a function of pressure and temperature. A temperature-dependence of the optical absorption spectrum was observed in samples with a constant Ho exp 3+ ion density. These data cannot be understood in terms of the generally used treatment of molar absorptivity, but requires the introduction of an effective oscillator strength. A temperature-dependent oscillator effect is also observed and this is interpeted as evidence for the presence of multiple species with differing oscillator strengths. The consequence of these observations for the determination of equilibrium constants for the different species will be discussed. (ERA citation 06:015860)