The (ν1, ν4, ν2+ν3, ν3+ν5) polyad of D328SiF around 1600 cm-1, studied by high-resolution FTIR spectroscopy

The nu(1) (A(1), 1578.31 cm(-1))/nu(4) (E, 1615.17 cm(-1)) Si-D stretching dyad of D3SiF has been studied by FTIR spectroscopy with a resolution of 2.4 x 10(-3) cm(-1). Only weak interactions of Coroilis (DeltaK = +/-1, Deltal = +/-1) and alpha resonance (DeltaK = +/-2, Deltal = -/+ 1) type between nu(1) and nu(4), and of l (2, -4) type within nu(4), were revealed. However, the nu(1) = 1 and nu(4) =1 levels were found to be severely perturbed by the nu(3) = nu(5) = 1 (E, 1590.37 cm(-1)) and nu(2) = nu(3) = 1 (A(1), 1604.25 cm(-1)) states. These perturbations are observable only near level crossings involving strong Coriolis and alpha interactions. The energy structure within these perturbers is severely complicated by strong Coriolis and alpha resonances and by l (2, 2), l (2, -1), and l (2, -4) interactions as already revealed by the nu(2)(A(1), 710.16 cm(-1)) and nu(5) (E, 701.72 cm(-1)) fundamentals. Interactions of the perturbing states with the nu(1)nu(4) dyad are particularly evident in local crossings. In total, 12 transitions belonging to the dark states and 68 perturbation-allowed transitions within the nu(1)/nu(4) dyad have been detected among the more than 5000 transitions that have been assigned for the nu(1)/nu(4) dyad, with J(max) and K-max of 50 and 30, respectively. Altogether about 85% of the assigned transitions were fitted with a standard deviation of 0.221 x 10(-3) cm(-1), leading to 61 parameters of the interacting polyad. (C) 2002 Elsevier Science (USA).