For gas phase organic molecules, ab initio composite methods exist that are able to predict accurate rovibrational spectra. Typically, fundamental vibrational frequencies can be obtained to within 1 cm-1 of known experimental values. However, the question remains as to whether a similar methodology can be developed for metal-bearing molecules. Rovibrational spectroscopic properties have been computed for the putative interstellar molecules magnesium acetylide (MgCCH) and its cation (MgCCH+). Using a “black box” coupled cluster theory-based quartic force field (QFF) with second-order vibrational perturbation theory, pure rotational spectra have been simulated at 15 K. Our QFF composite approach provides agreement to within 18 MHz (6.0 x 10-4 cm-1) for three rotational lines observed in the carbon-star envelope of IRC +10216 and tentatively assigned to neutral MgCCH. Neutral and cationic MgCCH spectroscopic results will also be compared to newly obtained data using Fourier transform infrared spectroscopy.

Rovibrational spectroscopy of magnesium acetylide (MgCCH) and its detection in the interstellar medium

2019 Fall National Meeting

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