VIBRATIONAL SPECTROSCOPY OF CS2− RADICAL ANION IN WATER

Janik, Ireneusz

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https://hdl.handle.net/2142/104404 Copy

Description

Title

VIBRATIONAL SPECTROSCOPY OF CS2− RADICAL ANION IN WATER

Author(s)

Janik, Ireneusz

Contributor(s)

Tripathi, G. N. R.

Issue Date

2019-06-18

Keyword(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.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/104404

DOI

10.15278/isms.2019.TD08

Copyright and License Information

Copyright 2019 Ireneusz Janik

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