The angleICI Bending Satellites in the Millimeter-Wave Rotational Spectra of CH(2)I(2) and CD(2)I(2).

Rotational transitions in the first four excited states of the low-frequency angleICI bending mode, nu(4), have been assigned in the mm-wave rotational spectra of CH(2)I(2) and of CD(2)I(2). Measurements of transition frequencies, made over the frequency region 167-326 GHz and for J" up to 190, allowed determination of sextic level spectroscopic constants for all states. The changes in spectroscopic constants with vibrational excitation show very small anharmonicity, in spite of the very low frequency of this mode (121 cm(-1)). Vibrational excitation affects the moments of inertia in such a way that the planar moment P(b), about the plane perpendicular to both angleICI and angleHCH, is practically invariant. Vibrational change in P(c), the moment along the principal axis in the HCH plane and perpendicular to the angleHCH bisector, has been successfully reproduced with an ab initio harmonic force field so that there is no discernible vibrational change in angleHCH on excitation of angleICI. Finally, the change in P(a) leads to estimated vibrational change of +0.12 degrees in the value of angleICI itself. Copyright 2000 Academic Press.

The Rotational Spectrum of CBrClF2 (Halon BCF): II. The Lowest Excited Vibrational States and Nuclear Quadrupole Coupling Tensors

The analysis of the millimeter-wave rotational spectrum of the well-known halon molecule CBrClF2 was extended to rotational transitions in the excited vibrational states v9 = 1 (307 cm-1) and v5 = 1 (337 cm-1). The two states are appreciably coupled by a- and b-axis Coriolis interaction which was treated explicitly and spectroscopic constants were determined from measurements at frequencies from 121 to 330 GHz and J" from 18 to 111. The present work, together with our previous study (1996. J. Mol. Spectrosc. 177, 240-250), results in accurate constants in the rotational Hamiltonian for the four lowest vibrational states of C79Br35ClF2 and C81Br35ClF2. The double nucleus hyperfine structure in low-J transitions of the two 35Cl isotopomers of CBrClF2 was also measured in the region 3-14 GHz with a supersonic beam, cavity Fourier transform microwave spectrometer. All constants in both the inertial and the principal nuclear quadrupole coupling tensors have been determined for both Br and Cl nuclei. Copyright 1997 Academic Press. Copyright 1997Academic Press

The Gas-Phase Electric Dipole Moments of the Symmetric Top Tertiary Butyl Molecules (t)BuX, X=F, Cl, Br, I, CN, and NC.

The electric dipole moments of symmetric top tertiary butyl derivatives were determined from Stark effect measurements made with cavity Fourier transform microwave spectroscopy under conditions of supersonic expansion. The resulting values are 1.9562(15), 2.1817(16), 2.2574(17) and 2.2122(17) D for tertiary butyl fluoride, chloride, bromide, and iodide, and 4.0129(30), and 4.0640(31) for tertiary butyl cyanide and isocyanide, respectively. The experimental values are compared with ab initio calculations and with experimental and calculated dipole moments for the corresponding methyl derivatives. Copyright 2001 Academic Press.