Search

Your search keyword '"Chambaud, G."' showing total 264 results
Start Over Author "Chambaud, G."
264 results on '"Chambaud, G."'

54. Reaction of CN–with F, Cl, O, andS Atoms: Attachment or Associative Detachment?

Author

Khiri, D. and Chambaud, G.

Subjects
*POTENTIAL energy surfaces, *ELECTRONIC structure, *HALOGENS, *INTERSTELLAR medium, *COUPLING reactions (Chemistry)
Abstract

Highly correlated ab initio wavefunctions within the UCCSD(T)-F12approach have been used to map the potential energy surfaces (PESs)describing the reactivity of the CN–(X1Σ+) anion with neutral atoms presentin interstellar media (F, Cl, O, and S). With the H atom, for comparison,the reaction [CN–(1Σ+) + H(2S)] evolves along the PES of the X2Σ+electronic ground state of HCN–(or HNC–) until the crossing withthe X1Σ+electronic groundstate of HCN (or HNC), where electron detachment occurs. The processis rather similar to the two halogen atoms F and Cl, with some differencesdue to the larger electron affinity of the halogens, making possiblethe existence of ClCN–in a 2Σ+state. The reaction of CN–with O and Satoms proceeds via a multistep mechanism. The lowest electronic stateat long distance, the 3Π state arising from the [CN–(1Σ+) + O/S(3P)] reaction channel, does not correlate with the X1Σ+ground state of the XCN–anion (X = O or S). This 3Π state and its bentcomponents cross at medium RXC(RXN) distances the X1Σ+ground state of XCN–or XNC–, and at shorter distances the X2Π state of the neutral XCN or XNC where the extra electroncan detach. With both O and S atoms, it is shown that the spin–orbitcouplings can efficiently lead the [CN–(1Σ+) + O/S(3P)] reaction toward the stable X1Σ+ground state of XCN–and XNC–. [ABSTRACT FROM AUTHOR]

Published
2015
Full Text
View/download PDF

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

Author

Khiri, D., Gritli, H., Peterson, K.A., and Chambaud, G.

Subjects
WAVE functions, AB-initio calculations, POTENTIAL energy, CHEMICAL stability, MATHEMATICAL functions
Abstract

Highly correlatedab initiowave functions within the UCCSD(T)-F12 approach have been used to map portions of the potential energy surfaces and to study the stability of the first excited triplet states of the NCS−/CNS−and NCO−/CNO−anions. Thesea3Π states for linear geometries, or their3A′ and3A″ bent components, correlate with the lowest dissociation asymptote of NCX−(X = S and O) along the NC-X coordinates. TheX1Σ+linear ground states of these anions are known to be stable with respect to dissociation to theX2Π ground state of the corresponding neutral molecule with a rather large electron affinity. Thea3Π state of the NCS−anion is positioned below theXstate of the neutral at long NC-S distances and its minimum of energy is found for bent geometries. The stability of its two components in bent geometries has been investigated, and it is found that some anionic forms are stable with respect to theXstate of the neutral. The linear CNS−and CNO−isomers present a minimum only at long CN−X distances, located below the minimum of their corresponding neutral CNX ground states. [ABSTRACT FROM PUBLISHER]

Published
2015
Full Text
View/download PDF

100. Ab initio study of the first excited state and of the transition of CNO

Author

Léonard, C. and Chambaud, G.

Subjects
*POTENTIAL energy surfaces, *DIPOLE moments, *ABSORPTION, *PHYSICAL & theoretical chemistry
Abstract

Abstract: The potential energy surface of the electronic state of CNO is calculated using the cc-pVQZ/MRCI+Q method. The rovibrational levels are determined variationally up to 18000cm−1 above the electronic ground state zero energy point and are used with the transition dipole moment surfaces, obtained with the cc-pVQZ/CASSCF method, in order to model the rovibrational absorption spectrum at 5K which is compared with the measurement of Bondybey et al. [V.E. Bondybey, J.H. English, C.W. Mathews, R.J. Contolini, Chem. Phys. Lett. 82 (1981) 208]. [Copyright &y& Elsevier]

Published
2008
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results