2024 - Sustainable Industrial Processing Summit
SIPS 2024 Volume 16. Intl. Symp on Electrochemistry, Molten Salts, Corrosion, Recycling and Battery
| Editors: | F. Kongoli, C.A. Amatore, R. Fehrmann, G. Kipouros, I. Paspaliaris, G. Saevarsdottir, R. Singh, R. Gupta, M. Halama, D. Macdonald, F. Wang, M. Barinova, F. Ahmed, C. Gaidau, X. Guo, K. Kolomaznik, H. Ozgunay, K. Tang, N.N. Thanh, S. Yefremova, K. Aifantis, Z. Bakenov, C. Capiglia, V. Kumar, A. U. H. Qurashi, A. Tressaud, R. Yazami |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2024 |
| Pages: | 243 pages |
| ISBN: | 978-1-998384-34-1 (CD) |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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OPTICAL SPECTROSCOPY OF CHLORINE GAS
Artem Kolobov1; Alexei Potapov2; Vladimir Khokhlov2;1JSC «DINUR», Pervouralsk, Russian Federation; 2INSTITUTE OF HIGH TEMPERATURE ELECTROCHEMISTRY, Ekaterinburg, Russian Federation;
Type of Paper: Regular
Id Paper: 173
Topic: 13
Abstract:
Chlorine gas is one of the most important reagent and product of many chemical reactions and technological processes involving molten salts, it is also often used in organic chemistry and photochemistry. Data on the optical spectroscopy of gaseous chlorine obtained over a wide temperature range provide additional information about the properties of chlorine and its reactivity.
Electronic absorption spectra (EAS) of chlorine gas were recorded in the range of 8333÷50000 cm-1 (200÷1200 nm). The spectrum consists of a single broad absorption band located mainly in the range 20000÷43500 cm-1 (230÷500 nm). There is no absorption in the range of 500÷1200 nm. The spectra were recorded in the temperature range from 0 to 1000°C approximately every 100 degrees.
With increasing temperature, the optical density of the absorption band decreases, and the position of the maximum shifts slightly (~ 1 nm per 100 degrees) to the short wavelength region [1]. The shape of the absorption band does not change significantly, although there is a tendency to the band broadening with increasing temperature. As the temperature rises, gaseous chlorine expands and fewer chlorine molecules enter the light beam. To compensate the influence of density change, all further considerations will be carried out in extinction units , dm2/mol.
If the parameters of the potential curves, between which electronic-vibrational transitions occur, are specified, then the question arises what transitions will be more likely and what transitions will be less likely. The excitation of the Cl2 molecule (20277 cm-1) is caused by the transition from the ground state X^1 ∑_g^+▒Cl_2 to the antibonding 1ПuCl2 state [2], which is accompanied by the dissociation of the molecule. Unlike an atom, a molecule consists of two connected subsystems; these subsystems move at significantly different speeds. The set of electrons is a fast subsystem, the set of nuclei is a slow one. Thus, in the process of electronic-vibrational transitions, the molecule finds itself in an excited electronic state at the same value of the internuclear distance r, in which it was caught in the act of absorption. Halogen molecules represent a rare case where r* r. It is obvious that in this case the most probable transitions (v=0 v*=n) are accompanied by a significant increase in the reserve of vibrational energy, and the high-frequency edge of the electronic-vibrational spectrum can become continuous, which corresponds to transitions in the section of the upper potential curve lying above the dissociation boundary. Under such conditions, the chlorine molecule dissociates as a result of a significant relative shift of the stable functions U(r) along the r axis rather than due to a transition to an unstable potential curve.
In the early 1950s, Sulzer and Wieland [3] proposed an equation describing the temperature dependence of extinction in the Franck-Condon approximation, which, however, did not describe the temperature shift of the absorption band maximum. Later, Golovitsky and Mikhailov [4] proposed an amendment that takes into account the displacement of the maximum with increasing temperature. This shift is apparently a consequence of the manifestation of anharmonic vibrations of the diatomic chlorine molecule [5].