High-Resolution FTIR and Millimeter-Wave Study of D(3)SiF: The Ground, v(3) = 1, and v(6) = 1 and 2 States

Rovibrational Interaction and Vibrational Constants of the Symmetric Top Molecule14NF3

Several accurate experimental values of the α^C and α^B rotation-vibration interaction parameters and ω_i, x_ij, and g_ij vibrational constants have been extracted from the most recent high-resolution Fourier transform infrared, millimeter wave, and centimeter wave investigations in the spectra of the oblate symmetric top molecule ¹⁴NF₃. The band-centres used are those of the four fundamental, the overtones, the combination, and hot bands identified in the region between 400 cm⁻¹ and 2000 cm⁻¹. Comparison of our constants with the ones measured previously, by infrared spectroscopy at low resolution, reveals orders of magnitude higher accuracy of the new values. The agreement between our values and those determined by ab initio calculations employing the TZ2Pf basis is excellent.

High-Resolution Infrared and Millimeter-Wave Study of D(3)SiF: The Ground and v(3)=1 States of the (29)Si and (30)Si Species, and the v(3)=v(6)=1 and v(3)=2 States of D(3) (28)SiF

The nu(3) band of D(3)SiF near 890 cm(-1) recorded with a resolution of 2.4x10(-3) cm(-1) has been explored for the (29)Si and (30)Si isotopic species. Moreover, the nu(3)+nu(6)-nu(6) and 2nu(3)-nu(3) bands for the main (28)Si isotopomer have been assigned. For this purpose the nu(3)+nu(6) and 2nu(3) bands at 1435.697 and 1769.531 cm(-1) have been studied. Ground state parameters of the (29)Si and (30)Si species have been determined by merging newly measured MMW frequencies and ground state combination differences. In addition, v(3)=1 excited state parameters for these species have been obtained. While for the (28)Si species the v(3)=v(6)=1 state is locally perturbed by levels of the v(2)+v(5)=2 polyad, the v(3)=2 state appears to be unperturbed, its parameters being predictable from those of the v(3)=1 state. Anharmonicity constants x(33)=-4.1334 cm(-1) and x(36)=-3.6547 cm(-1) have been determined. Copyright 2001 Academic Press.

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.