The interacting upsilon(6)=2 levels of (D3SiCl)-Cl-35: A tool to determineground state constants from high-resolution spectra in the 440-590 and 900-1100 cm(-1) regions

High-resolution FTIR spectra of monoisotopic (D3SiCl)-Cl-35 have been recor ded in the regions 440-590 cm(-1) (nu(3)/nu(6)) and 900-1100 cm(-1) (2 nu(6 )/nu(3) + nu(6)/2 nu(3)), A detailed rovibrational study was done for the 2 nu(6)(0) 2 nu(6)(-/+2), and 2 nu(3) overtone bands and for the 2 nu(6)(+/- 2)-nu(6)(+/-1), 2 nu(6)(0)-nu(6)(-/+)1, and (nu(3) + nu(6)(+/-1))-nu(6)(+/- 1) hot bands. For the first time the interactions occurring between the nu( 6) = 2, nu(3) = nu(6) = 1, and nu(3) = 2 levels of any trideuterated silyl halide have been analyzed. The (nu(3) + nu(6)(+/-1))-nu(6)(+/-1) hot band s erved to obtain accurate energies of the nu(3) = nu(6) = 1 level, the nu(3) + nu(6) combination band not being detectable on our spectra. The first ex perimental determination of A(o) and D-K(o) for this molecule was undertake n by a well-established method, using the nu(6), 2 nu(6)(+/-2)nu(6)(+/-1), and 2 nu(6)(-/+2) bands. Ground state energy differences Delta K(J) = E-o( J, K) - E-o(J, K - 3) were calculated for K values from 2 to 16. By a least -squares fit of 163 such differences, the A(o) and D-K(o) values thus obtai ned were (in cm(-1)): A(o) = 1.4278230(8) and D-K(o) = 5.3916(31) x 10(-6). (C) 1999 Academic Press.