We report the coupling of a flash pyrolysis molecular beam source with nonresonant strong-field ionization in a time-of-flight mass spectrometer. The saturation laser intensities at which ionization occurs for the various product species are generally found to correlate closely with the ionization energies, as has been seen for closed-shell molecules. It is then possible to use this correlation to identify the product and quantify isomers from among several candidate species whose ionization energies are known. The approach is analogous to using tunable vacuum ultraviolet ionization to identify reaction products.