Pulse pyrolysis infrared laser jet spectroscopy of free radicals

A new, combined, pulse pyrolysis supersonic jet and infrared diode laser absorption experiment has been developed for the study of free radicals. The ν2 fundamental band of the methyl radical has been detected in this experiment using a pulsed nozzle/laser frequency modulation technique. The high nozzle temperature (1500 K) and short contact time (<20 μs) produce a high-density, clean methyl radical source. The rotational temperature of CH3 was measured to be between 30 and 45 K, indicating efficient cooling after the expansion. The minimum detectable absorption coefficient is estimated to be 3×10−6 cm−1.