Time-resolved wavelength modulation spectroscopy measurements of HO kinetics

摘要

High-frequency wavelength modulation spectroscopy (WMS) has been applied to the detection of the hydroperoxyl radical (HO↓(2)) in a lager photolysis and long-path absorption pump-probe kinetics reactor with a near-infrared distributed feedback diode laser. The HO↓(2) is formed by the 355-nm photolysis of Cl↓(2) in the presence of CH↓(3)OH and O↓(2) and monitored by a phase-sensitive detection of the second-harmonic (2f) signal in the 2v↓(1) band with a 1.5μm diode laser directly modulated at 5 MHz. The measured 2fWMS signal is calibrated by direct absorption and converted to an absolute number density with the known absorption line strength of the HO↓(3) line at 6625.80 cm↑(-1). The utility of time-resolved WMS as a second-order kinetics probe is demonstrated through the measurement of the HO↓(2) self-reaction rate constant at 295 K. # 1997 Optical Society of America