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Single-particle pulse radiolysis using muons

TitleSingle-particle pulse radiolysis using muons
Publication TypeJournal Article
Year of Publication1996
AuthorsWalker, DC
JournalRadiation Physics and Chemistry
Volume47
Pagination23-28
Date PublishedJan
Type of ArticleProceedings Paper
KeywordsAQUEOUS-SOLUTIONS, ATOMS, ELECTRON-SPIN EXCHANGE, GASES, HYDROGEN ISOTOPES, LIQUID HYDROCARBONS, radicals, relaxation, WATER
Abstract

Muonium is the light hydrogen-like atom produced at the end of high energy tracks of positive muons in many media. It is observed via its unique spin-polarization decay characteristics. This paper discusses two recent developments in muonium chemistry: (i) the mechanism of muonium formation in superfluid helium and solid nitrogen; and (ii) a fast spin-depolarization interaction of muonium with a Cr(III) complex. (i) He and N-2 are among the few chemicals in which the initial dispersement of muons does not involve ’’hot-atom’’ reactions. They also happen to undergo sharp increases in electron mobility on passing between different phases at specific low temperatures. Recently published data on these two media suggest that muonium is formed in a ’’delayed’’ mechanism, over tens of nanoseconds, through charge neutralization of the muons by electrons which were created some distance back down the radiolysis track. (ii) Kinetic isotope effects based on muonium vs H-1 reactions in water indicate almost the same upper diffusion-limited rates. The case discussed here is that of an aqueous millimolar solution of Cr(NCS)(4)(NH3)(2)(-) which reacts by catalysing the electron-spin conversion of muonium. When spin-hip probabilities are coupled with solvent-caging effects for this process, the value obtained seems to make this the fastest muonium encounter rate yet seen, 5 x 10(10) M(-1) S-1.

URL<Go to ISI>://A1996TC69500005