| 16626196 |
Kummli DS, Frey HM, Leutwyler S: Femtosecond degenerate four-wave mixing of carbon disulfide: high-accuracy rotational constants. J Chem Phys. 2006 Apr 14;124(14):144307.
Femtosecond degenerate four-wave mixing (fs-DFWM) rotational coherence spectroscopy (RCS) has been used to determine the rotational and centrifugal distortion constants of the 00 (0) 0 ground and 01 (1) 0 vibrationally excited states of gas-phase CS (2). RCS transients were recorded over the 0-3300 ps optical delay range, allowing the observation of 87 recurrences. The fits yield rotational constants B (00 (0) 0)=3.271 549 2 (18) GHz for (12) C (32) S (2) and B (00 (0) 0)=3.175 06 (21) GHz for the (12) C (32) S (34) S isotopomer. The rotational constants of the degenerate 01 (1) 0 bending level of (12) C (32) S (2) are B (01 (1) 0)=3.276 72 (40) and 3.279 03 (40) GHz for the e and f substrates, respectively. These fs-DFWM rotational constants are ten times more accurate than those obtained by CO (2) laser/microwave heterodyne measurements and are comparable to those obtained by high-resolution Fourier transform infrared spectroscopy. Ab initio calculations were performed at two levels, second-order Moller-Plesset theory and coupled-cluster singles, doubles, and iterative triples [CCSD (T)]. The equilibrium and vibrationally averaged C=S distances were calculated using large Dunning basis sets. An extrapolation procedure combining the ab initio rotational constants with the experiment yields an equilibrium C=S bond length of 155.448 pm to an accuracy of +/-20 fm. The theoretical C=S bond length obtained by a complete basis set extrapolation at the CCSD (T) level is r (e)(C=S)=155.579 pm, or 0.13 pm longer than that in the experiment. |
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