S-33 Nuclear quadrupole coupling in the microwave spectrum of methylthiocyanate

The rotational spectrum of S-33-methylthiocyanate in the vibrational ground state was observed in natural abundance by molecular beam Fourier transform microwave (MB-FTMW) spectroscopy. We were able to determine the relational and centrifugal distortion constants, the methyl internal relation parameters, and the N-14 and S-33 quadrupole coupling constants. The rotational constants were found to be A = 15 598.104(83)MHz, B = 4144.5631(3) MHz and C = 3338.1246(2) MHz. For the torsional ground state (A-species) the S-33 nuclear quad rupole coupling constants were obtained chi(aa) = -40.513(4)MHz, chi(bb) = -7.166(6)MHz and chi(cc) = 47.679 (7) MHz. The corresponding constants for the E-species lines agree with these values within the given error limits. Additionally the rotational and centrifugal distortion constants, the methyl internal rotation, and the N-14 quadrupole coupling constants for the S-32- and S-34-isotopomer could be improved.