Rotational Spectroscopy of Simple Metal Carbon Clusters: Resolving the Beauty of Fine and Hyperfine Interactions in Metal Monoacetylides and Metal Carbides

Abstract

Pure rotational spectra of simple metal carbon clusters that relevant to transition metal synthesis and catalysis have been obtained using Fourier transform microwave (FTMW) techniques combined with millimeter-wave direct-absorption methods. Rotational spectra of metal acetylides (CuCCH, ZnCCH, Li/Na/KCCH, MgCCH, AlCCH, CrCCH), diatomic metal monocarbide (CrC) and T-shape metal dicarbides (YC₂ and ScC₂) were recorded in the 4–650 GHz frequency regime. Measurements of weaker isotoplogues including ⁶⁶ZnCCH, ⁶⁸ZnCCH, Zn¹³C¹³CH, ZnCCD, Li/Na/KCCD, CrCCD, Y¹³C¹²C, Y¹³C¹³C, Sc¹³C¹³C, were also studied to aid in structural determinations. This work is the first study of ZnCCH and ScC₂ by any type of spectroscopic technique. Hyperfine splittings in MgCCH and Li/Na/KCCH have also been resolved and the weak isotoplogues of YC₂ have been measured for the first time. Potential interstellar molecules ScO and FeCN were studied using the FTMW techniques in the 4–62 GHz frequency regime. Spectra of the zinc insertion product ClZnCH₃ were additionally recorded in the 10–30 GHz (FTMW) and 260–296 GHz (direct absorption) frequency ranges, along with weaker isotopologues Cl⁶⁶ZnCH₃ and Cl⁶⁸ZnCH₃. This works is the first measurement of zinc insertion products using the FTMW-DALAS techniques. The data were analyzed implementing an effective Hamiltonian, allowing for accurate spectroscopic parameters to be established. From rotational constants, the molecular geometries were accurately determined. Electronic properties were also assessed, including the degree of covalent vs ionic character in a chemical bond, and the molecular orbital composition. The fundamental physical and chemical properties of these benchmark species were obtained in order to gain insight into their role in larger molecular systems, test theoretical calculations, and, in certain cases, provide accurate rest frequencies for astronomical searches.