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Title:VIBRATIONAL SPECTROSCOPY OF CS2− RADICAL ANION IN WATER
Author(s):Janik, Ireneusz
Contributor(s):Tripathi, G. N. R.
Subject(s):Radicals
Abstract:Recent transient Raman studies of the CO$_{2}$$^{-}$ radical in water have led to the vibrational properties of this important radical intermediate. More importantly the evidence of the electron being shared between the bent CO$_{2}$ and its hydration shell at an energy of about \~{} 0.28 eV above the ground electronic state is obtained. The corresponding electronic state has a life-time of several femtoseconds, consistent with the theoretical value. No evidence of non-equivalence of the two CO bonds was found, which suggested that the partially detached electron is symmetrically situated between CO$_{2}$ and the water molecule. Because of the electron not being localized on CO$_{2}$, the Raman scattered photon does not terminate into a vibrational state corresponding to the CO$_{2}$$^{-}$ overtones above 0.28+/-0.03 eV or higher.$^{1}$ Now in a follow up study, we have examined its sulfur analogue CS$_{2}$$^{-}$. We have prepared the radical anion in water by pulse radiolysis with Raman detection up to 4000 \wn to monitor its vibrational fingerprints. The Raman spectrum, excited in the resonance with the 270 nm ($\lambda$$_{max}$) absorption of CS$_{2}$$^{-}$ is dominated by a very strong band at 666 \wn, associated with the symmetric C-S stretching vibration, its overtones, and combinations with SCS bending vibration of 330 \wn. Solvation shell bending and stretching modes are also enhanced, suggesting contribution to the excited state of the radical anion analogous to CO$_{2}$$^{-}$. From the progression of overtones, and the first order anharmonicity of 2.57\wn, we estimate a continuum of vibrational states at an energy of roughly 5.4 eV. Unlike CO$_{2}$$^{-}$, CS$_{2}$$^{-}$ did not show any evidence of electron detachment up to the energies of ~0.5eV. DFT calculations reproduced experimental frequencies fairly well predicting a molecular geometry of CS$_{2}$$^{-}$ with CS bond lengths of 1.638\AA and CSC angle of 143.3$^{o}$. (1) Janik I.,Tripathi G.N.R.; The nature of the CO$_{2}$$^{-}$ radical anion in water. J. Chem. Phys. 2016, 144, 154307.
Issue Date:2019-06-18
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Type:Text
Language:English
URI:http://hdl.handle.net/2142/104404
DOI:10.15278/isms.2019.TD08
Rights Information:Copyright 2019 Ireneusz Janik
Date Available in IDEALS:2019-07-15
2020-01-25


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