A photochemical model of ozone interference effects in laser detection of tropospheric OH

This is the authors' abstract. We don't add key points for this paper.

Laser‐generated interference in the laser‐induced fluorescence detection of tropospheric hydroxyl is addressed by a detailed photochemical model. This phenomenon arises through photolysis of ozone by the detection laser and subsequent reaction of O(1D) with H2O to form OH. The approach is direct time integration of the coupled differential equations describing the pertinent chemical reactions, collisional energy transfer, and photolytic and spectroscopic processes, including an assessment of limitations due to uncertainties in the input parameters. The goal is to use the model to quantitatively design OH detection methods so that the experimental results need not rely on such a model for interpretation. Previously reported measurements of tropospheric OH appear to have been contaminated by ozone interference effects and by optical saturation of the monitoring transition. However, suggested improvements can reduce the problem to interference levels below 2×105 OH molecules/cm3, permitting measurements useful for testing theories of fast tropospheric photochemistry.