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Quantum Yield of the Iodide/Iodate Chemical Actinometer: Dependence on Wavelength and Concentration



R O. Rahn, M I. Stefan, J R. Bolton, E Goren, Ping-Shine Shaw, Keith R. Lykke


The quantum yield (QY) of the iodide/iodate chemical actinometer (0.6 M KI/ 0.1 M K103) was determinedirradiation between 214 run and 330 mu. The photoproduct, triiodide, was determined flum the increase iabsorbance at 352 run, which together with a concomitant measurement of the UV fluence enabled the QY tocalculated. The QY at 254 mn was determined to be 0.75 0.02 when calibration was carried out against a NIStraceable radiometer or photometric device. At wavelengths below 254 mn, the QY increased slightly leveling oat -0.80 +/- 0.05, while above 254 mu the QY decreases linearly with wavelength reaching a value of 0.30 at 28mn. In addition, the QY was measured at different iodide concentrations. There is a slight decrease in QY goinfrom 0.6 to 0. 1 5 M KI, while below 0. 1 5 M KI the QY drops off sharply, decreasing to 0.23 by 0.006 MCalibration of the QY was also done using potassium ferrioxalate actinometry to measure the irradiance. Thesresults showed a 20% reduction in QY between 240 run and 280 mn as compared with radiometry. Thdiscrepancy suggests that the QY of the ferrioxalate actinometer in this region of the spectrum neereexamination.
Photochemistry and Photobiology
No. 2


actinometry, iodide/iodate, photochemistry, quantum yield, UV


Rahn, R. , Stefan, M. , Bolton, J. , Goren, E. , Shaw, P. and Lykke, K. (2003), Quantum Yield of the Iodide/Iodate Chemical Actinometer: Dependence on Wavelength and Concentration, Photochemistry and Photobiology, [online], (Accessed May 21, 2024)


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Created July 31, 2003, Updated October 12, 2021