Abstract
Conventional Fourier-transform infrared spectrometer (FTIR) cannot detect species with short lifetime. We employed step-scan FTIR coupled with ac/dc detection and multiple reflection of both IR probe beam and UV photolysis beam to establish time-resolved FTIR absorption spectrometry so as to detect in the laboratory several unstable gaseous species that are important in atmospheric chemistry: ClCO, ClCS, ClSO, CH3SO2, C6H5SO2, CH3OO, ClCOOH, CH3SO, and CH3C (O) OO via their IR absorption. The system is capable of 10 ns temporal resolution and 0.13 cm^(-1) spectral resolution, but for radical studies we typically employed 1μs temporal resolution and 1 cm^(-1) spectral resolution to obtain spectra with improved S/N ratio.