High-Resolution Spectrum and Rovibrational Analysis of the nu(2)/nu(5) Dyad of D(3)SiF near 700 cm(-1)

The nu(2) (A(1), 710.157 cm(-1)) and nu(5) (E, 701.717 cm(-1)) fundamental bands of D(3)(28)SiF have been studied by FTIR spectroscopy with a resolution of 2.4 x 10(-3) cm(-1). We assigned 1648 lines for the parallel band (J(max) = 50, K(max) = 21), 4279 for the perpendicular band (J(max) = 52, K(max) = 27), and in addition 671 perturbation-allowed transitions (J(max) = 50, K(max) = 12). The nearly degenerate v(2) = 1 and v(5) = 1 states are linked by (DeltaK = +/-1, Deltal = +/-1) and (DeltaK = +/-2, Deltal = -/+1) interactions, while the l(5) = +/-1 levels of nu(5) interact also by l(2, -1), l(2, 2), and l(2, -4) interactions. The first model with 36 free parameters, taking into account all these resonances through a nonlinear least-squares program, gave standard deviations of 1.56 x 10(-4) cm(-1) for 5997 nonzero-weighted IR data and 138 kHz for 8 MW data from the literature. The second model, in which the main Coriolis term was constrained to a force field value, used 37 parameters and gave similar standard deviations. A new determination of the A(0) and D(0)(K) ground state parameters was performed by two methods: either using differences between "forbidden" transitions differing by 3 in K or letting A(0) and D(0)(K) free in the global fit. The values obtained are fully compatible with those obtained previously by the "loop method." Copyright 2000 Academic Press.