Potassium sulphate crystals containing chromate ions show two broad bands in the region 2300-2650 Å and 3300-3750 Å. These bands contain a fine structure of alternately weak and strong lines. The set of strong lines is due to transitions from the ground state to vibrational levels of the excited state. The set of weaker lines is due to transitions from one of the vibration frequencies of the ground electronic state to vibration frequencies of the upper electronic state. © 1971.

K. P. Pande

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Optical properties of chromate ion in potassium sulphate crystals

Chemical Physics Letters

Optical and infrared spectra of dichromate ions in KC1, KBr, and KI matrices are reported. Optical spectra of Cr2O7 -- consist of three absorption bands that are attributed to the electronic transitions 1A1(t1 6)→1T2(t13t 21);1A1(1t 16)→1E(t15t 21)or 1T2(t1 5t21); and 1A1(t 16)→1T2(t1 5e1) on the basis of molecular orbitals. Fine structure caused by coupled vibration-electronic transitions is observed in the 1A1(t16)→1T 2(t15e1) band. This fine structure further splits at low temperature (77°K) because of the symmetry lowering of the dichromate ion from T'd to C3v. Infrared spectra show a number of lines. A model that assumes that the dichromate ion enters the lattice by replacing two halide ions with no charge compensating vacancy satisfactorily explains all the experimental results.

Fulltext

The Journal of Chemical Physics

Electronic and vibrational spectra of Cr2O7 ions in potassium halide matrices

Vibrational frequencies of CrO 42− ion embedded in orthorhombic sulphates have been determined from optical and infrared absorption studies. In the optical absorption spectra, the electronic levels are found to have a superposed vibration structure, in the regions 2300 to 2750 Á and 3300 to 3850 Á, with alternate strong and weak lines. The set of strong lines is interpreted to be due to the transitions from the ground electronic state to the vibrational levels of the excited state, whereas the set of weaker lines is assigned to the transitions from one of the vibrational levels of the ground electronic state to the vibrational levels of the upper excited electronic state. It is found that the IR forbidden bands become allowed and are observed in these lattices. No splitting is observed in the degenerate modes in IR spectra. Copyright © 1973 WILEY‐VCH Verlag GmbH & Co. KGaA

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Optical Properties of CrO 42− Ion in Orthorhombic Sulphates

Two electronic bands arising from the t1 → 2e and t1 → 3t2 transitions are observed in the region ≈ 360 nm and ≈ 250 nm in alkali halide crystals doped with Cr2O2-7. These bands split and also show well resolved fine structure at 77°K. The fine structure is explained on the basis of vibrational frequencies superimposed on electronic spectra. Infra-red spectra of these crystals show three prominent bands. © 1972.

Journal	Chemical Physics Letters
ISSN	00092614
Open Access	No