ROTATIONAL SPECTRUM OF CD2I2 - AN ISOTOPOMER OF THE FIRST MOLECULE CONTAINING 2 IODINE NUCLEI INVESTIGATED BY MICROWAVE SPECTROSCOPY

The rotational spectrum of CD2I2 was measured and analyzed by combinin g results from two different millimeter wave spectrometers. Low-J tran sitions were measured with a free jet spectrometer at conditions of co mpletely resolved hyperfine structure over the frequency range 59-69 G Hz. High-J rotational transitions were measured at room temperature at frequencies 167-338 GHz and for J '' up to 190 ''. Spectroscopic cons tants in the sextic rotational Hamiltonian of CD2I2 have been determin ed, and the analysis of the observed hyperfine structure yielded all c omponents in the inertial and in the principal nuclear quadrupole coup ling tensors for the iodine nuclei. The rotational constants for CD2I2 and those for CH2I2 from Z. Kisiel, L. Pszczolkowski, W. Caminati, an d P. G. Favero (1996. J. Chem. Phys. 105, 1778-1785) have been used to evaluate a full r(o) structure and have been combined with the result s of ab initio calculations to also evaluate the average r structure: r(CI) = 2.1364(6) Angstrom, r(CH) = 1.078(2) Angstrom, angle(ICI) = 1 13.83(5)degrees, and angle(HCH) = 113.3(3)degrees. The current results complete the first analysis of a rotational spectrum of a molecule co ntaining two iodine nuclei. (C) 1998 Academic Press.