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New computational and experimental studies have been carried out for the MgCCH radical in its X2Σ+ state. Coupled cluster theory [CCSD(T)], was used in conjunction with post-CCSD(T) and scalar relativistic additive corrections to compute vibrational quartic force fields for MgCCH and its cation. From the quartic force fields, higher-order spectroscopic properties, including rotational constants, were obtained. In tandem, the five lowest energy rotational transitions for MgCCH, N = 1→0 through N = 5→4, were measured for the first time using Fourier transform microwave/millimetre wave methods in the frequency range 9–50 GHz. The radical was created in the Discharge Assisted Laser Ablation Source (DALAS) developed in the Ziurys group. A combined fit of these data with previous millimetre direct absorption measurements have yielded the most accurate rotational constants for MgCCH to date. The computed principle rotational constant lies within −1.51 to +1.65 MHz of the experimental one, validating the computational approach. High-level theory was then applied to produce rovibrational spectroscopic constants for MgCCH+, including a rotational constant of B0 = 5354.5–5359.5 MHz. These new predictions will further the experimental study of MgCCH+, and aid in the low-temperature characterisation of MgCCH in the interstellar medium. [ABSTRACT FROM AUTHOR]

The article focuses on research investigating the chemical composition of the supergiant star VY Canis Majoris conducted at the University of Arizona's Steward Observatory in Tucson. Astronomers Lucy Ziurys, Nick Woolf and Stefanie Milam at the university, were discussing how gas clouds that surround old stars contribute to the origins of life. With the installation of a new receiver in their radio telescope they have explored into the oxygen-rich envelope of the said star.

The most-studied organocopper, methylcopper (CH3Cu), has been synthesized for the first time as a monomer, free of other ligands or coordinated solvent, and detected using millimeter-wave rotational spectroscopy. The molecule was created in the gas phase by the reaction of copper vapor and several different precursors, including CH4 and tetramethylsilane. An obvious symmetric top pattern was observed, indicative of C3v, symmetry. For confirmation, rotational spectra of four isotopically substituted species, 65Cu12CH3, 63Cu12CD3, 63Cu13CH3, and 65Cu13CH3, were recorded as well, following large-scale syntheses of specifically labeled precursors. From this data set, accurate spectroscopic constants and a structure for CH3Cu were derived. The rm(2) geometry shows the shortest alkyl carbon-copper(1) bond length known (1.8809 Å) and a rather large H-C-H angle in the methyl group (109.88°). The measured rotational and distortion constants are well reproduced by QCISD calculations. This study should allow further refinement of theoretical calculations on methylcopper and other organocopper derivatives, which are valuable synthetic intermediates in organic chemistry. [ABSTRACT FROM AUTHOR]

The methylzinc hydride molecule, HZnCH3, has been observed in the gas phase for the first time in the monomeric form using high-resolution spectroscopic techniques. The molecule was synthesized by two methods: the reaction of dimethylzinc with hydrogen gas and methane in an AC discharge and the reaction of zinc vapor produced in a Broida-type oven with methane in a DC discharge. HZnCH3 was identified on the basis of its pure rotational spectrum, which was recorded using millimeter/submillimeter direct-absorption and Fourier transform microwave techniques over the frequency ranges 332-516 GHz and 18-41 GHz, respectively. Multiple rotational transitions were measured for this molecule in seven isotopic variants. K-ladder structure was clearly present in all of the spectra, indicating a molecule with C3v, symmetry and a ¹A1 ground electronic state. Extensive quadrupole hyperfine structure arising from the 67Zn nucleus was observed for the H67ZnCH3 species, suggesting covalent bonding to the zinc atom. From the multiple isotopic substitutions, a precise structure for HZnCH3 has been determined. The influence of the axial hydrogen atom slightly distorts the methyl group but stabilizes the Zn-C bond. This study suggests that HZnCH3 can be formed through the oxidative addition of zinc to methane in the gas phase under certain conditions. HZnCH3 is the first metal-methane insertion complex to be structurally characterized. [ABSTRACT FROM AUTHOR]

The simplest alkali metal acetylides MCCH were made in the gas phase for the first time (see drawing), and their bond lengths were determined by millimeter/submillimeter spectroscopy of their isotopomers. The M-C bond lengths r CM are the shortest known for organoalkali metal compounds. In the case of LiCCH, the experimentally determined Li-C distance of 1.888 Å has an estimated accuracy of ±0.0005 Å, which should allow a rigorous test of theoretical methods., (© 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)