Atomic hydrogen reaction rates in aqueous solution via free-induction decay attenuation

This new pulsed EPR method is providing data on H-atom reaction rates in water, which are important in radiation chemistry of aqueous solutions, eg, corrosion in reactor cooling systems, H2 production in high-level radioactive waste, and spread of radioactive iodine following the Chernobyl accident. This AECL-Argonne collaborative effort was undertaken to investigate fundamental aqueous H-atom chemistry for the purpose of developing predictive models of iodine transport that will be used by the nuclear power industry to enhance plant safety. Reactions of (H)aq with many representative organic and inorganicmolecules have already been investigated. Radiolysis of aqueous solns with 3-MeV electrons produces H atoms in high yield; in the free induction decay method, a powerful 30 ns microwave pulse is applied immediately following pulse radiolysis, creating a phase coherence of the H-atom electron spins that is detected in the pulsed EPR spectrometer as a damped cosine free induction decay (FID). Natural decay time of the spin coherence is many microseconds, but if a reaction partner for the H atoms is introduced, the FID becomes shorter, revealing the H reaction rate. Results of H atom reaction with benzene, methanol, periodate and periodic acid are discussed briefly