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NCS: AN AB INITIO MOLECULAR ORBITAL STUDY.
TSUNEO HIRANO AND UMPEI NAGASHIMA, Grid Technology Research Center, Institute of Advanced Industrial Science and Technology, 6-9-3 Ueno, Taito-ku, Tokyo 110-0015, Japan; TINA ERICA ODAKA AND PER JENSEN, FB 9 -- Theoretische Chemie, Bergische Universität -- Gesamthochschule Wuppertal, D-42097 Wuppertal, Germany.
Much is not known for NCS, while its sister molecule NCO is a quite familiar molecule for high resolution molecular spectroscopy and is known as one of the typical molecules to show the Renner effect. Molecular constants of X 2
NCS are known, but there has been a discrepancy between theoretically predicted and experimentally determined rotational constants. At the MR-SDCI+Q and MR-ACPF levels with the full-valence active space, our calculated B0 values were smaller by at least 0.4 % than experimentally observed B0 value, as is the case reported by Ouazbir, et al .b When the core-valence correlation is included, this situation was improved to give an error of 0.05% in Be and B0. The predicted Be and B0, though preliminary at the moment, at the level of core-valence MR-SDCI+Q/aug-cc-pCVQZ are 6113.9 and 6103.5 MHz, respectively, against the experimental B0 valuea of 6106.62162(25) MHz. The N-C and C-S equilibrium bond lengths are predicted to be 1.178 and 1.632 Å, respectively, and hence the B0 of the isotopemer NC34S could be 5959 MHz.