Abstract

Reaching low temperatures is of great interest for precision spectroscopy, as it simplifies rovibrationnal spectra of large molecules. Efficient cooling can be achieved via the supersonic expansion of a gas through a nozzle, which can be probed using cavity-enhanced spectroscopy [4]. The comb filtered by the cavity had a f_rep= 707MHz, and two-burst interferograms were acquired, yielding comb mode resolution [4]. A mixture of 90% Ar and 10% C₂H₂ was expanded from a reservoir at 16 Torr into a chamber at 0.35 Torr through an aerospike nozzle. The isentropic core of the resulting supersonic jet exhibited a rotational temperature of 140 K and was surrounded by shear layers and residual gas at room temperature.

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