We report the use of time-resolved frequency modulation (FM) spectroscopy for the measurement of photochemically generated radicals. CN radicals from the 193 nm photodissociation of cyanogen (NCCN) have been detected using a phase-modulated cw Ti:sapphire ring laser, probing single rotational lines of the A (2) Pi <-- X (2) Sigma system. The combination of sensitivity with time and frequency resolution is more than adequate to record Doppler-broadened line shapes of collisionless photofragments. Significant signal-to-noise enhancement is demonstrated compared to a dual-beam transient absorption technique.