title: Relativistic spin-orbit coupling effects on secondary isotope shifts of (13)C nuclear shielding in CX(2) (X = O, S, Se, Te).
abstract: Rovibrational corrections, temperature dependence, and secondary isotope shifts of the (13)C nuclear shielding in CX(2) (X = O, S, Se, Te) are calculated taking into account the relativistic spin-orbit (SO) interaction. The SO effect is considered for the first time for the secondary isotope shifts. The nuclear shielding hypersurface in terms of nuclear displacements is calculated by using a density-functional theory method. Ab initio multiconfiguration self-consistent field calculations are done at the equilibrium geometry for comparison. (13)C NMR measurements are carried out for CS(2). The calculated results are compared with both present and earlier experimental data on CO(2), CS(2), and CSe(2). The heavy-atom SO effects on the rovibrational corrections of (13)C shielding are shown to be significant. For CSe(2) and CTe(2), reliable prediction of secondary isotope effects and their temperature dependence requires the inclusion of the SO corrections. In particular, earlier discrepancies of theory and experiment for CSe(2) are fully resolved by taking the SO interactions into account.
authors.affiliation: NMR Research Group, Department of Physical Sciences, P.O. Box 3000, FIN-90014 University of Oulu, Finland.
authors.forename: Perttu
authors.initials: P
authors.lastname: Lantto
authors.forename: Juha
authors.initials: J
authors.lastname: Vaara
authors.forename: Anu M
authors.initials: AM
authors.lastname: Kantola
authors.forename: Ville-Veikko
authors.initials: VV
authors.lastname: Telkki
authors.forename: Bernd
authors.initials: B
authors.lastname: Schimmelpfennig
authors.forename: Kenneth
authors.initials: K
authors.lastname: Ruud
authors.forename: Jukka
authors.initials: J
authors.lastname: Jokisaari