FTIR study of the ν1/ν4 bands of D3Si35Cl near 1600 cm-1

The nu(1) (A(1), 1583.22 cm(-1)) and nu(4) (E, 1615.33 cm(-1)) Si-D stretching bands of monoisotopic (D3SiCl)-Cl-35 have been studied by FTIR spectroscopy with a resolution of 3.3 x 10(-3) cm(-1). We have assigned 2341 rovibrational lines for nu(1) (J(max) = 70, K-max = 19) and 6207 for nu(4) (J(max) = 75, K-max = 27). Both (DeltaK = +/-1, Deltal = +/-1) and (DeltaK = +/-2, Deltal = -/+1) interactions connect the nu(1) = 1 and nu(4) = 1 levels, the latter exerting moreover a weak l(2, 2) interaction. These interactions were taken into account in a nonlinear least-squares fit, refining 29 free parameters with a standard deviation of 0.257 x 10(-3) cm(-1) over 6722 nonzero-weighted data. Blended lines and about 250 of the 330 lines belonging to the K = 11 subband of nu(1) and the K DeltaK = -6 subband of nu(2) were zero-weighted because they are locally perturbed respectively by the neighboring upper states of the 2nu(3) + nu(6) (E, 1561.95 cm(-1)) and 3nu(3) (A(1), 1604.81 cm(-1)) bands. Equivalent fits were obtained for altogether three different models obeying constraints according to the theory of unitary equivalent reductions of the rovibrational Hamiltonian. By means of a band contour simulation both the transition moment ratio \M-1 : M-4\ = 0.67 and a positive sign of the Coriolis intensity perturbation were determined. (C) 2002 Elsevier Science (USA).