Level Crossing Resonance Spectroscopy Research Articles

ChemInform Abstract: Conformational s-cis/trans Isomerization of Free Radicals Observed by Muon Level Crossing Resonance Spectroscopy

ChemInform Abstract: Conformational s-cis/trans Isomerization of Free Radicals Observed by Muon Level Crossing Resonance Spectroscopy

Erratum: Loss of muonium in nonhomogeneous process studied by level-crossing resonance

Level-crossing resonance spectroscopy has been used to determine the yield of muonium atoms formed in water and in hexane through production of muonated free radicals. In the presence of high concentrations of solutes, which yield radicals, all muons injected into the solutions are found either in diamagnetic molecules or free radicals. However, at low concentrations, the free-radical yield was smaller and a missing fraction appeared. Inverse yield against inverse concentration plots were not linear, indicating that reactions leading to loss occurred with nonhomogeneously distributed species from the muon's expanding track.

Muon diffusion and spin dynamics in copper.

We have studied the quantum diffusion of positive muons in pure copper over the temperature range 12 mK\ensuremath{\le}T\ensuremath{\le}150 K using the technique of muon-spin relaxation. The rate of diffusion has been deduced from its effect upon the muon-polarization function. The measurements were made in a weak longitudinal external magnetic field, where the spin relaxation has proved to be the most sensitive to the muon hop rate below 150 K. Our results for the behavior of the muon hop rate are well explained by the recently developed theories for the quantum diffusion of light interstitials in metals by Kondo, Yamada, and others. These theories stress the effects of the conduction electrons in the metal in providing a form of ``friction,'' retarding the diffusion process. In addition, we have utilized the technique of level-crossing resonance spectroscopy, by measuring the electric-quadrupole interaction strength of the copper nuclei. These results have enabled us to show that the muon occupies the same octahedral site at all the temperatures studied, ruling out the possibility of metastable muon sites contributing to any significant portion of the muon polarization in the temperature range studied.

Conformational s-cis/trans isomerization in free radicals observed by muon level crossing resonance spectroscopy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConformational s-cis/trans isomerization in free radicals observed by muon level crossing resonance spectroscopyMary V. Barnabas, Krishnan Venkateswaran, and David C. WalkerCite this: J. Am. Chem. Soc. 1990, 112, 20, 7163–7167Publication Date (Print):September 1, 1990Publication History Published online1 May 2002Published inissue 1 September 1990https://doi.org/10.1021/ja00176a013RIGHTS & PERMISSIONSArticle Views80Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (586 KB) Get e-Alerts Get e-Alerts

Loss of muonium in nonhomogeneous processes studied by level-crossing resonance

Level-crossing resonance spectroscopy has been used to determine the yield of muonium atoms formed in water and in hexane through production of muonated free radicals. In the presence of high concentrations of solutes, which yield radicals, all muons injected into the solutions are found either in diamagnetic molecules or free radicals. However, at low concentrations, the free-radical yield was smaller and a "missing fraction" appeared. Inverse yield against inverse concentration plots were not linear, indicating that reactions leading to loss occurred with nonhomogeneously distributed species from the muon's expanding track.

Muonated cyclohexadienyl radicals observed by level crossing resonance in dilute solutions of benzene in hexane subjected to muon-irradiation

Benzene is used here as a scavenger of muonium to produce the muonated cyclohexadienyl radical in dilute solutions in n-hexane. The radical was identified by level crossing resonance spectroscopy (LCR) by observing the proton resonance of the —CHMu group occuring at 2.059T. Its yield is found to equal the sum of the muonium atom yield and the “missing” muon yield in hexane (total 35% of the incident muons). Consequently, the complete dispersement of muons in different chemical associations is now accounted for in a saturated hydrocarbon liquid, and is seen to be similar to that in water.

Muon level crossing resonance study of radical formation in allylbenzene, styrene and toluene

All chemical states of the muons in a μSR experiment have now been determined in toluene, allylbenzene and styrene. There are no “missing fractions” because the sum of the various muon-containing free-radicals equals 1- P D, where P D is the directly formed diamagnetic fraction. Use of the new technique of level crossing resonance spectroscopy has enabled yields to be determined and identification of individual isomeric radicals. For toluene, there is a total radical fraction of 0.77 and a distribution of 2.5:2:1 for ortho: meta: para addition within the ring. For allylbenzene, ≈ 70% of the muonated radicals are side chain addition products and of these nearly 40% have Mu on the second C; and, for the 30% adding to the ring, there is virtually no selectivity of site as the o: m: p ratio is the statistical ratio 2:2:1. Toluene and allylbenzene, however, differ dramatically from styrene. In styrene, 82% of the muons form radicals and 85% of these arise from formal addition of muonium to the end C of the side chain to give muonated phenylethyl radicals. The remaining 15% are seen to be distributed (2:1) between the ortho and para positions of the ring, with no addition at the meta position. The high degree of preference shown by styrene indicates strong selectivity in achieving the most stable radical. Proton hyperfine couplings for all of these radicals have also been determined.