Nearly all kinetics studies report the observed rate of reactant disappearance, with product identity and branching largely unknown. This limitation arises from considerable experimental challenges inherent in the quantitative detection of the full range of products of a given reaction, particularly for large polyatomic systems. Recent advances have relied upon tunable synchrotron photoionization or low-energy electron impact ionization to achieve selective product detection in dynamics, kinetics, and flame studies. Challenges remain, however, as these studies require fitting of composite and often incompletely resolved spectra to infer branching, and clear product signatures are often lacking. To address these issues, we have developed an alternative approach, which incorporates chirped-pulse Fourier transform microwave spectroscopy in low-temperature uniform supersonic flows (“Chirped-Pulse in Uniform Flow”, C-PUF). This technique provides clear quantifiable spectroscopic signatures of polyatomic products in bimolecular or unimolecular reactions for virtually any species with a modest electric dipole moment.