Variation In Photon Flux During Extended Photochemical Aerosol Experiments: Implications For Atmospheric Laboratory Simulations
Actinometry, Aerosols, Benzene, Methane, Photochemical haze, Titan
Journal of Photochemistry and Photobiology A: Chemistry
In order to simulate the interaction of sunlight with planetary atmospheres, including Pluto, Titan and the early Earth, many laboratory studies have used high-power broadband lamps with spectral features that extend into the vacuum-ultraviolet (VUV, <200 >nm) to initiate photochemistry relevant to the atmosphere of interest. In many cases, experiments are run on the order of hundreds of hours with no accounting for how the photon flux within the system may be evolving with lamp age or a possible buildup of films over optical surfaces when working with high-yield photochemical systems. Given that the nature of photochemistry depends on the ratio of photons to reactants, variations in flux must be taken into account if the system is to be fully understood. In this study, standard N2O actinometry was used to measure the VUV flux of high-intensity deuterium lamps before, during, and after the photochemical synthesis of Titan analog aerosols made from methane or benzene precursors. It was found that VUV photon flux can be decreased by over 50% in under 10 h at higher number densities, with recorded flux losses of over 75% during extended (>60 h) photochemical experiments. While this is only one model system, it is apparent that changes in photon flux during simulations must be taken into account if adequate comparisons of the photochemical kinetics to their respective planetary environments are to be made.
Department of Chemistry and Biochemistry
Original Publication Date
DOI of published version
UNI ScholarWorks, Rod Library, University of Northern Iowa
Sebree, Joshua A.; Wayson, Jessica M.; and Lopez, Jose R., "Variation In Photon Flux During Extended Photochemical Aerosol Experiments: Implications For Atmospheric Laboratory Simulations" (2018). Faculty Publications. 703.