Actinometer

Abstract: Photophysics of Organic Molecules in Solution Introduction Electronic States Radiative Transitions Nonradiative Transitions Excited State Kinetics Acknowledgments Bibliography Transition Metal Complexes Electronic Structure Types of Excited States and Electronic Transitions Absorption and Emission Bands Jablonski Diagram Photochemical Reactivity Electrochemical Behavior Polynuclear Metal Complexes Photophysical Properties of Organic Compounds Photophysics of Organic Molecules in Solution Triplet-State Energies: Ordered Flash Photolysis: Designing Experiments Low-Temperature Photophysics of Organic Molecules Absorption and Luminescence Spectra of Organic Compounds ESR and ODMR Parameters of the Triplet State Photophysical Properties of Transition Metal Complexes Photophysical Parameters Absorption and Emission Spectra Abbreviations Rate Constants of Excited-State Quenching Ionization Energies, Electron Affinities, and Reduction Potentials Ionization Energies and Electron Affinities Reduction Potentials Bond Dissociation Energies Solvent Properties Donor Number Luminescence Spectroscopy Measurements Correction of Luminescence Intensity Measurements in Solution Fluorescence Quantum Yield Standards Phosphorescence Quantum Yield Standards Luminescence Lifetime Standards Light Sources and Filters Spectral Distribution of Photochemical Sources Transmission Characteristics of Light Filters and Glasses Chemical Actinometry Ferrioxalate Actinometer Photochromic Actinometers Reinecke's Salt Actinometer Uranyl Oxalate Actinometer Other Actinometers Miscellaneous Spin-Orbit Coupling Hammett ? Constants Fundamental Constants and Conversion Factors Index *References included in each chapter

Abstract: This document updates the first version of the IUPAC technical report on "Chemical actinometers" published in Pure Appl Chem 61, 187-210 (1989) Since then, some methods have been improved, procedures have been modified, and new substances have been proposed as chemical actinometers An actinometer is a chemical system or a physical device by which the number of photons in a beam absorbed into the defined space of a chemical reactor can be determined integrally or per time This compilation includes chemical actinometers for the gas, solid, microheterogeneous, and liquid phases, as well as for the use with pulsed lasers for the measurement of transient absorbances, including the quantum yield of phototransformation, as well as the literature for each of the actinometers The actinometers listed are for the use in the wavelength range from the UV to the red region of the spectrum A set of recommended standard procedures is also given Advantages and disadvantages are discussed regarding the use of chemical actinometers vs electronic devices for the measurement of the number of photons absorbed Procedures for the absolute measurement of incident photon flux by means of photodiodes are also discussed

Abstract: A chemical actinometer has been devised whose high sensitivity and precision depends upon the spectrophotometric determination of the photolysis products of potassium ferrioxalate with 1:10 phenanthroline. The sensitivity is some hundreds of times greater than that of the uranyl oxalate actinometer. The behaviour of the actinometer has been investigated in detail at 3650 to 3663 A, and tests also show that it is suitable for use over a wide range of wavelengths. The approximate quantum efficiency has been determined at twelve wave-lengths between 4900 and 2537 A. The advantages and possible applications of the actinometer in the measurement of small doses of radiation are discussed.

Abstract: The generation of hydroxyl (•OH) radicals plays a key role in the heterogeneous photocatalytic degradation of organic pollutants in aqueous suspensions of TiO2. The quantum yield of this process is thus an important parameter; however, it is not easy to measure in a particulate system arising from problems caused by light scattering from the particles. In this work, a reliable method for the determination of the quantum yield of hydroxyl radical production in heterogeneous systems has been developed, based on measurements of •OH radical generation rates and the photon flux absorbed by TiO2 suspensions. In this procedure, a modified integrating sphere method was used to determine the true fraction of light absorbed by TiO2 suspensions. A ferrioxalate chemical actinometer was used to measure the incident photon flux. As a check on the quantum yield method, good agreement with known literature values was obtained for quantum yield measurements of the photochemical generation of the p-benzosemiquinone (BQ•-) ...