Vapor complexation in the CsI–HoI3 system up to 1300 K and the f ← f hypersensitive transition intensities of Ho(III) in different coordination geometries
✍ Scribed by G.N. Papatheodorou; A. Chrissanthopoulos
- Publisher
- Elsevier Science
- Year
- 2007
- Tongue
- English
- Weight
- 493 KB
- Volume
- 832
- Category
- Article
- ISSN
- 0022-2860
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✦ Synopsis
Electronic absorption spectroscopy is used in the temperature range 850-1300 K, to study the vapor species over molten HoI 3 -CsI (1:1), molten CsI and solid HoI 3 . Quantitative absorbance measurements are used to calculate the following enthalpies of transition: DH subl (HoI 3 ) = 271 ± 3 kJ mol À1 , DH vap. (CsHoI 4 ) = 155 ± 2 kJ mol À1 and DH vap. (CsI) = 151 ± 2 kJ mol À1 . The ligand field components of the 5 G 6 ‹ 5 I 8 hypersensitive transition of Ho(III) for the three different, all iodide, coordination geometries of HoI 3 (g), CsHoI 4 (g) and HoI 6 3À (in molten CsI) have been examined in detail. The molar absorptivities (e) and oscillator strengths (f) increase as the coordination decreases from the ''octahedral'' HoI 6
3À (e = 65 L mol À1 cm À1 ; f = 99 • 10 À6 ) to the distorted tetrahedral HoI 4
À (e = 235 L mol À1 cm À1 ; f = 290 • 10 À6 ) to the trigonal HoI 3 (e = 390 L mol À1 cm À1 ; f = 500 • 10 À6 ). The main factors affecting the hypersensitive transition intensities are the coordination number and symmetry and the ligand polarizability as well as the Boltzmann population effects on the ground state levels which are responsible for the appearance of ''hot'' bands in the spectra. A C 2v symmetry is anticipated for the CsHoI 4 (g) with the HoI 4 À ''tetrahedra'' distorted towards a square planar symmetry leading to a structure with a pseudo-like inversion center.