A Chirped Pulse Fourier Transform Microwave Spectrometer with Multi-Antenna Detection

The construction of a new chirped pulse Fourier transform microwave (CP-FTMW) spectrometer with multiple-antenna detection (MAD) is reported. The instrument design and execution represent a completely new approach to possibly increasing sensitivity in CP-FTMW spectroscopy as it does not involve increased sampling, power, or passes of microwaves with the molecular sample. This is particularly advantageous for experiments where only one sampling point is available. The MAD-CP-FTMW or “MAD Chirp” is demonstrated on both linear molecule carbonyl sulfide (OCS) and asymmetric-top molecule 1,3-difluorobenzene (DFBZ) with detection points at the broadcast antenna as well as in the quadrature to the traditional receiving antenna. Signal-to-noise comparisons with each sample at each detection point have been made and are reported. Experiments demonstrating the signals detected in these new positions are molecular and not an artifact of a reflection are reported. Although this represents a first step to a possible new approach to addressing CP-FTMW sensitivity, no sensitivity increase based on this method is currently reported.