High signal to noise microwave spectra can be used to unambiguously determine the structure of each molecule in a gas phase mixture. Until recently, this technique has been used primarily to determine the structure of known samples, where quantum chemistry calculations can typically predict molecular geometry to within a few percent. We present new methods to extend this technique to unknown samples, where the structure must be determined without prior knowledge of the compounds under analysis. The methods leverage the unprecedented high signal-to-noise of our buffer-gas cooled microwave spectrometer, which is can be used both on stable species and highly reactive species of astrochemical significance. The high density and low noise temperature of this source allows us to record microwave spectra at unprecedented sensitivity, with a dynamic range in excess of one million achievable in a few minutes of integration time. This high sensitivity enables new protocols in both 1-D and 2-D microwave spectroscopy, including automated spectral assignment via broad 2-dimensional searches. We will present these spectra and the computational tools we are developing to unravel these complex datasets to determine the geometry of the carbon atoms of each compound within our initially unknown sample.

High sensitivity microwave spectroscopy via cryogenic buffer gas cooling

256th National Meeting (2018)

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