Chirped-Pulse Microwave Spectroscopy

Technical Details

Broadband chirped-pulse Fourier Transform microwave (CP-FTMW) spectroscopy uses fast digital electronics from the communications industry to create chirped-pulses of microwave radiation that can interrogate rotational transitions spread over wide frequency ranges (2=8 GHz or 8-18 GHz) simultaneously. Using fast digitizers, the free-induction decay from the molecular sample is detected, signal-averaged, and Fast Fourier Transformed to obtain the spectrum in the frequency domain. We combine CP-FTMW detection with a time-of-flight mass spectrometer (TOFMS) that can be used to photo-ionize the same sample mixture under identical conditions, thereby enabling correlations to be drawn between the masses of the reactive intermediates and their microwave transitions (see Figure 1).

Key Contributions

Chirped-pulse Fourier Transform microwave spectrometer
Chirped-pulse Fourier Transform microwave spectrometer

We are using these methods to study free radicals and transient intermediates formed in reactive mixtures of relevance to combustion, atmospheric chemistry, CO2 sequestration, and space. We are also expanding our capabilities to include a cryogenically cooled buffer gas cell designed to make and study reactive intermediates and gas phase complexes with increased sensitivity.

PIs: Timothy Zwier, Nils Hansen, Lenny Sheps