RESUMO
The nu4+/-1 + 2nu60 and nu4-/+1 + 2nu6+/-2 perpendicular components and the nu4+/-1 + 2nu6+/-2 parallel component of the CH379Br isotopomer have been found and studied in high resolution (0.006 cm-1). Both perpendicular components are linked altogether and also to the nu2 + nu3 + nu4 band by anharmonic resonances. A model taking these anharmonic resonances and l(2,2) resonances into account has been used. It allowed to obtain a r.m.s. deviation of 0.0065 cm-1 in a least squares fit over 1327 lines (46 being zero-weighted) belonging to the three components of nu4 + 2nu6 and to the calculated KDeltaK = -1 sub-band of nu2 + nu3 + nu4 deduced from the corresponding observed sub-band of nu2 + nu3 + nu4 - nu3. Copyright 1997 Academic Press. Copyright 1997Academic Press
RESUMO
With a resolution of 4.4 x 10(-3) cm-1, we were able to identify in this range the very weak nu2 + 2nu04 (A1) component near 1180 cm-1, the nu3 + nu4 band around 1205 cm-1 with its (A1 + A2) and E very intermixed components, and the nu1 + nu4 (E) band centered at 1238 cm-1. Three thousand six hundred transitions belonging to the (nu3 + nu4, nu1 + nu4) interacting system were fitted together with a model taking into account l(2, 2) interactions inside nu1 + nu4 and between (A1 + A2) and E components of nu3 + nu4, the l-vibrational resonance inside nu3 + nu4(A1 + A2), and the Coriolis interactions between nu1 + nu4 and nu3 + nu4(A1 + A2) on one hand and between nu1 + nu4 and nu3 + nu4 (E) on the other. Four available MW transitions were also included in the fit. A rms of 0.76 x 10(-3) cm-1 was obtained with 34 free parameters among 38. Normally the Fermi resonance, which links nu3 to nu2 + nu4 with a coupling term W234 = 2.86 cm-1, must connect each component of nu3 + nu4 with each component of nu2 + 2nu4. But since we have only little experimental information about the weak nu2 + 2nu04 component (120 assigned lines) and none about the dark nu2 + 2nu+/-24 component, it was not possible to introduce this resonance in the fit. However, the bandcenters' shifts were calculated since the basic coupling term W234 and the anharmonic constant x24 are well known. Therefore, according to this approximation, the very sensitive anharmonic constants x34 and g34 could be deduced. Of course the x14 Fermi-independent constant, derived directly from the (nu1 + nu4)0 bandcenter given by the fit, was certainly more accurate. Copyright 1998 Academic Press.
RESUMO
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.
RESUMO
The nu(6) (555.453 cm(-1)), the nu(3) (888.899 cm(-1)), and the very weak 2nu(6) infrared bands (2nu(-/+2)(6) 1101.734 cm(-1), 2nu(0)(6) 1100.102 cm(-1)) for the (28)Si species of D(3)SiF have been recorded with a resolution of 3.3, 2.4, and 5.0 x 10(-3) cm(-1), respectively. Millimeter-wave spectra up to 640 GHz of D(3)SiF in the ground, v(3) = 1, and v(6) = 1 and 2 states were measured. Ground state constants complete up to H constants including the K-dependent parameters A(0), D(0)(K), and H(0)(K) as obtained by the nu(+/-1)(6)/2nu(+/-2)(6)-nu(+/-1)(6)/2nu(-/+2)(6) loop method were determined by a merge of 2388 ground state combination differences with 59 rotational data. The v(3) = 1 and v(6) = 1 and 2 levels appear to be unperturbed intervibrationally for the J and K values that could be accessed. However, Deltal = Deltak = +/-2 and Deltal = +/-2, Deltak = -/+4 interactions affect the v(6) = 1 level while the v(6) = 2 levels undergo three interactions of Deltal = Deltak = +/-2, Deltal = +/-2, Deltak = -/+1 and Deltal = +/-4, Deltak = -/+2 type. Typically, for the different bands, 2000-4000 pieces of infrared data augmented by 36-120 rotational data were fitted together. Owing to the weakness of the 2nu(6) band, the body of v(6) = 2 data was enlarged by energies that are deduced from the 2nu(6)-nu(6) and nu(6) bands and which span in particular high K values. Comparison with available ab initio data derived from the harmonic and anharmonic force fields is made. Copyright 1999 Academic Press.