In a chirped-pulse experiment, a rapid sweep of the microwave radiation excites molecules over a 3 GHz frequency span. This allows us to rapidly scope out large segments of the microwave spectrum all at once and greatly reduces spectral search time. The excitation and detection elements are incorporated into our existing microwave cavity spectrometer, giving us the capability of doing both types of experiments on the same instrument. We can switch between the two in a matter of minutes without having to break vacuum.
Shown below is a 10-16 GHz portion of the spectrum obtained when studying acetic sulfuric anhydride. This spectrum was taken in an expansion of acetic acid and SO3 seeded in argon. Transitions of different species are highlighted in red, blue, and green (acetic sulfuric anhydride, Ar-SO3, and acetic acid monomer, respectively.)
