# High Sensitivity Microwave Spectroscopy in a Cryogenic Buffer Gas Cell

## TL;DR

This paper presents a cryogenic buffer gas cell microwave spectrometer capable of high-resolution, high-sensitivity analysis of complex mixtures across a broad frequency range, with rapid data acquisition and versatile sample input methods.

## Contribution

The authors introduce significant improvements in operating range, sensitivity, and sample versatility for microwave spectroscopy in a cryogenic buffer gas cell, enabling faster analysis of complex mixtures.

## Key findings

- Extended frequency range from 12-18 GHz to 12-26 GHz.
- Achieved detection sensitivity comparable to high Q cavity spectrometers.
- Recorded broadband spectra up to 3000 times faster than traditional methods.

## 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 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 sample consumption rate.