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Are there stable excited triplet states of NCS-/CNS- and NCO-/CNO-?

Abstract : Highly correlated ab-initio wave functions within the UCCSD(T)-F12 approach have been used to map the Potential Energy Surface (PES) and to study the stability of the first excited triplet states of the NCS−/CNS− and NCO−/CNO− anions. These a3Π states for linear ge- ometries or their 3A′ and 3A” bent components correlate with the lowest dissociation asymptote of NCX− (X = S and O) along the NC-X coordinates. The X1Σ+ linear ground state of these anions is known to be stable with respect to the X2Π linear ground state of the corresponding neutral molecule with a rather large Electron Affinity (EA), calculated 3.57 eV and 3.70 eV for NCS and NCO respectively, in good agreement with previous experimental and theoretical data. The a3Π state of the NCS− anion is positioned below the X2Π state of the neutral at long NC-S distances and on contrary to the linear X2Π state of the neutral, the minimum of energy of the a3Π state is found for bent geometries with an angle close to 140 degree : the stability of its two components, 3A′ and 3A”, in bent geometries, has been discussed and it is found that some anionic forms are stable with respect to the X2Π state of the neutral. The absolute minima of the triplet states have been determined. Only for NCS−, it is found that the absolute minimum of the 3A′ triplet state is below the minimum of the neutral X2Π state. The linear CNS− and CNO− isomers present a minimum at long distance, located below the minimum of their corresponding neutral CNX ground states.
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Contributor : Gilberte Chambaud <>
Submitted on : Tuesday, September 19, 2017 - 2:11:14 PM
Last modification on : Wednesday, October 28, 2020 - 2:20:03 PM


  • HAL Id : hal-01590240, version 1



Khiri Dorra, Hager Gritli, Kirk A. Peterson, Gilberte Chambaud. Are there stable excited triplet states of NCS-/CNS- and NCO-/CNO-?. Molecular Physics, Taylor & Francis, 2015, 113 (13-14), pp.1534. ⟨hal-01590240⟩



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