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Abstract: We discuss the equilibrium structure of the hydrogen trioxy radical (HO3). The CCSD(T) geometry at the approximate basis set limit, in conjunction with the geometry obtained using the CCSDT method and a moderate basis set, suggests an equilibrium HO–OO bond length of approximately 1.59Å. [Copyright &y& Elsevier]

Abstract: Cyanoacetylene enriched in deuterium was used to record pure rotational transitions of DC3N and its rare 13C and 15N isotopic species by employing Fourier transform microwave (FTMW) spectroscopy on a supersonic-jet expansion at centimeter wavelengths (8.2–25.4GHz) and by using long-path absorption spectroscopy at millimeter and submillimeter wavelengths (82–900GHz). In addition, submillimeter wave measurements (304–897GHz) have been performed for DC3N in its lowest excited vibrational state. Hyperfine structure caused by the 14N and D nuclei has been resolved in the FTMW spectra. Quantum-chemical calculations have been performed on the hyperfine structure parameters at the coupled-cluster level (CCSD(T)) with up to core-polarized quintuple zeta basis-sets and were found to be in excellent agreement with experimental data as far as these were available. Vibrational corrections on the quadrupole coupling parameters have been evaluated at the MP2 level employing a quadruple zeta basis-set. The present and previous data were fit simultaneously to obtain accurate predictions for the identification of these species in space. [Copyright &y& Elsevier]