A white cell based broadband transient UV-vis absorption spectroscopy with pulsed laser photolysis reactors for chemical kinetics under variable temperatures and pressures.

The article focuses on the design, characterization, and performance of a novel broadband ultraviolet-visible (UV-vis) absorption spectroscopy apparatus coupled with a pulsed-laser photolysis flow reactor for gas-phase chemical kinetics studies. The system features a jacketed glass flow reactor operating between 239–293 K and 10–550 Torr, integrated with a white cell multipass optical setup that enables a well-defined absorption pathlength (~450 cm) and simultaneous spectral and temporal measurements via a dual-exit spectrograph feeding an intensified CCD camera and a photomultiplier tube. The apparatus is validated through temperature profiling, equilibrium constant measurements of NO2/N2O4, and kinetic studies of the simplest Criegee intermediate (CH2OO) and its reactions with SO2 and NO2, showing good agreement with literature values. Unique aspects include the co-aligned photolysis and probe beams with reduced optical components for improved light intensity and flatness, as well as a purge flow design that protects reactor windows while maintaining accurate absorption pathlengths. This setup offers a balance of sensitivity, spectral coverage, and time resolution suitable for atmospheric and physical chemistry research under atmospherically relevant conditions.