High-resolution FTIR and millimeter-wave study of D3SiF: The ground, v(3)=1, and v(6)=1 and 2 states

The nu(6) (555.453 cm(-1)), the nu(3) (888.899 cm(-1)), and the very weak 2 nu(6) infrared bands (2 nu(6)(-/+2) 1101.734 cm(-1), 2 nu(6)(0) 1100.102 c m(-1)) for the Si-28 species of D3SiF have been recorded with a resolution of 3.3, 2.4, and 5.0 x 10(-3) cm(-1) respectively. Millimeter-wave spectra up to 640 GHz of D3SiF in the ground, upsilon(3) = 1, and upsilon(6) = 1 an d 2 states were measured. Ground state constants complete up to H constants including the K-dependent parameters A(0), D-K(0), and H-K(0) as obtained by the nu(6)(+/-1)/2 nu(6)(+/-2)-nu(6)(+/-1)/2 nu(6)(+/-2) loop method were determined by a merge of 2388 ground state combination differences with 59 rotational data. The upsilon(3) = 1 and upsilon(6) = 1 and 2 levels appear to be unperturbed intervibrationally for the J and K values that could be accessed. However, Delta l = Delta k = +/-2 and Delta l = +/-2, Delta k = - /+4 interactions affect the upsilon(6) = 1 level while the upsilon(6) = 2 l evels undergo three interactions of Delta l = Delta k = +/-2, Delta l = +/- 2, Delta k = -/+1 and Delta l = +/-4, Delta k = -/+2 type. Typically, for t he different bands, 2000-4,000 pieces of infrared data augmented by 36-120 rotational data were fitted together. Owing to the weakness of the 2 nu(6) band, the body of upsilon(6) = 2 data was enlarged by energies that are ded uced from the 2 nu(6)-nu(6) and nu(6) bands and which span in particular hi gh K values. Comparison with available ab initio data derived from the harm onic and anharmonic force fields is made. (C) 1999 Academic Press.