A Chirped Pulse Fourier Transform Millimeter Wave Spectrometer for Room Temperature, Gas Mixture Analysis

A new arbitrary waveform generator based, chirped pulse spectrometer for high- resolution, millimeter wave rotational spectroscopy of gas mixtures is presented. The spectrometer band covers the frequency range from 260 – 295 GHz, a favorable spectral window for room temperature analysis of small molecules with a molecular mass of less than 150 amu. The design leverages the state of the art in solid-state millimeter light sources and high-speed digital electronics to introduce significant advances for millimeter/submillimeter spectroscopy, which is conventionally addressed by direct absorption techniques. By efficient use of a high power millimeter wave light source, the chirped pulse spectrometer is 10,000 times faster than modern direct absorption counterparts. In addition to speed, the time resolved emission spectroscopy approach enables analytical tools that can be used to speed spectral assignment in unknown samples. Results of sensitivity, dynamic range, and chemical selectivity are presented using compressed gases as an initial benchmark followed by extensions to real gas mixtures. The results have implications to a broad set of basic science research applications and make a strong case for wider application to analytical challenges as a new commercial platform.