RESUMEN

The Fourier transform infrared spectrum of monoisotopic D3Si35Cl in the region of the nu2/nu5 band system was recorded with a resolution of 2.4x10(-3) cm-1. More than 9000 lines of the strongly Coriolis x,y-coupled bands, (nu2)0=701.936, and (nu5)0=688.898 cm-1, have been assigned, among them 276 forbidden but perturbation allowed transitions around avoided crossings according to Delta(k-l)=+/-3 mechanisms. Three different models taking into account redundancies in the framework of unitary equivalent reductions of the rovibrational Hamiltonian have been employed to fit the data. All three models reproduced consistently the full data set employing 28 refined parameters with an rms deviation of 0.31x10(-3) cm-1. The equivalence of the parameter sets was established by the agreement of parameter sums obtained with the different models. The analysis of the avoided crossings, together with the fit of the forbidden lines, allowed an independent determination of the ground state parameters A0 and D(K)0. Combined with existing data for nu1, nu3, nu4, and nu6, the present results allowed the determination of experimental values, Ae=1.4371895(94) and Be=0.19823049(59) cm-1. The experimental results are compared with those of previous ab initio calculations of the anharmonic force field.

Asunto(s)

Silanos/química , Espectrofotometría Infrarroja/métodos , Modelos Químicos , Modelos Estadísticos , Modelos Teóricos , Espectroscopía Infrarroja por Transformada de Fourier

RESUMEN

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.

RESUMEN

The first high-resolution study on germanium tetrafluoride is reported. We used a monoisotopic sample of (70)GeF(4). The FTIR spectra of the two infrared active fundamentals, namely the nu(4) (bending) and nu(3) (stretching) modes, were recorded at a temperature of ca. 210 K and a resolution (1/maximum optical path difference) of 0.0031 and 0.0023 cm(-1), respectively. These spectra were analyzed using the STDS software developed in Dijon. In both cases, we obtained a fit with a root mean square better than 1x10(-3) cm(-1). Both bands show very regular structures with no detectable perturbation. Copyright 2001 Academic Press.