ANALYSIS OF THE ROTATIONAL SPECTRA OF SIH3CN AND ITS ISOTOPOMERS - EXPERIMENTAL AND AB-INITIO DETERMINATIONS OF THE DIPOLE-MOMENT AND THE STRUCTURE

The ground state rotational spectra of SiH3CN and its Si-29, Si-30, C- 13, N-15, d(1), d(2), and d(3) isotopic species have been measured by Fourier transform microwave spectroscopy and by millimeterwave spectro scopy. Accurate rotational, centrifugal distortion, and N-14 and D nuc lear quadrupole coupling constants have been derived. The dipole momen t of the parent species has also been measured, mu = 3.4400(42) D. The structure, force field, dipole moment, and nuclear quadrupole couplin g constants have been calculated ab initio at the SCF, MP2, and B3LYP levels using triple zeta polarized basis sets. The experimental r(o), r(s), and r(z) structures have been determined. An approximate equilib rium structure has been obtained by combining the experimental results and the ab initio calculations: r(e)(C=N) = 1.159 Angstrom, r(e)(Si-C ) 1.848 Angstrom, r(e)(Si-H) = 1.470 Angstrom, and angle(HSiC) = 107.4 degrees. (C) 1998 Academic Press.