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Abstract:
We describe an instrument which can be used to analyze complex chemical mixtures at high resolution and high sensitivity. Molecules are collisionally cooled with helium gas at cryogenic temperatures (∼4–7 K) and subsequently detected using chirped pulse microwave spectroscopy. Here, we demonstrate three significant improvements to the apparatus relative to an earlier version: (1) extension of its operating range by more than a factor of two, from 12–18 GHz to 12–26 GHz, which allows a much wider range of species to be characterized; (2) improved detection sensitivity owing to the use of cryogenically cooled low-noise amplifiers and protection switches; and (3) a versatile method of sample input that enables analysis of solids, liquids, gases, and solutions, without the need for chemical separation (as demonstrated with a 12–16 GHz spectrum of lemon oil). This instrument can record broadband microwave spectra at comparable sensitivity to high Q cavity spectrometers which use pulsed supersonic jets, but up to 3000 times faster with a modest increase in the sample consumption rate.
