Detection of muonated free radicals through the effects of avoided level crossing. Theory and analysis of spectra

Heming, M.; Roduner, Emil; Pàtterson, B. D.; Odermatt, W.; Schneider, Jörg W.; Baumeler, Hanspeter; Keller, H.; Savić, I. M.

doi:10.1016/0009-2614(86)80154-3

Cited by 87 publications

(59 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An alternative technique, avoided level-crossing muon spin resonance (ALC-//SR) in longitudinal magnetic fields, allows the detection of radicals even when they are formed over periods of the order of a microsecond, provided that the transition rate is high enough to produce a siginificant ALC signal during the muon lifetime [13]. It is a time-integral technique which can use the full muon flux of the accelerator since there is no constraint on the number of muons within the sample at any given time.…”

Section: Introductionmentioning

confidence: 99%

Surface Dynamics of the Cyclohexadienyl Radical Adsorbed on Silica Gel Investigated Using Avoided Level-Crossing Muon Spin Resonance

Schwager¹,

Roduner²,

Reid³

et al. 1995

Zeitschrift Für Physikalische Chemie

Self Cite

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

Surface Dynamics of the Cyclohexadienyl Radical Adsorbed on Silica Gel Investigated Using Avoided Level-Crossing Muon Spin Resonance

Schwager¹,

Roduner²,

Reid³

et al. 1995

Zeitschrift Für Physikalische Chemie

Self Cite

View full text Add to dashboard Cite

“…A micelle-controlled mechanism would be given by reactions [5]- [7], A major problem in trying to extract k7 by "fitting" the data to eq. [lo] is the fact that the fraction of acetone in the aqueous phase relative to the micellar phase is a nonlinear function of [mic] because micelles undoubtedly become saturated with acetone (perhaps after 10 or 20 molecules).…”

Section: Discussionmentioning

confidence: 99%

“…It has also been well characterized by level-crossing resonance spectroscopy (pLCR) in the neat liquid state (7) and in dilute solutions in hexane and in water (4). It has an isotropic muon hyperfine coupling constant (Ap) of 26.1 MHz in neat acetone.…”

Section: Introductionmentioning

confidence: 99%

Micelle-induced change of mechanism in the reaction of muonium with acetone

Stadlbauer¹,

Venkateswaran²,

Gillis³

et al. 1996

Can. J. Chem.

View full text Add to dashboard Cite

Muonium atoms add to the 0 atom of the carbonyl group of acetone to give the muonated free radical (CH~)~C-O-MU when the reaction takes place in water or hydrocarbons, but not when the acetone is localized in micelles. Micelles have no effect on the formation of muonated cyclohexadienyl radicals when muonium reacts with benzene under similar conditions. The addition reaction with acetone appears to have been subsumed by a faster alternative reaction in the micellar environment. Evidence is presented for this interpretation rather than for an inhibition of the radical or for a shift in the muon level-crossing resonance spectrum with hydrogen (muonium) bonding, though major shifts are seen for the spectrum of this radical in pure solvents of widely different dielectric constant. It is suggested that muonium's "abstraction" reaction takes over in micelles because significant micelle-induced enhancement effects were previously observed in that type of reaction. The data are consistent with a rate constant for the abstraction reaction of muonium with acetone in micelles of >6 x lo8 M-' SKI.Key words: muonium, kinetic isotope effects, micelle enhancement, HMu-addition, H M u abstraction.RCsumC : Lorsqu'on opkre en solution dans I'eau ou dans les hydrocarbures, les atomes de muonium s'ajoutent h I'atome d'oxygkne du groupe carbonyle de l'acitone pour conduire h un radical muone (CH~)~C-O-MU; ce n'est toutefois pas le cas lorsque l'acitone est localisie dans des micelles. Les micelles n'ont aucun effet sur la formation de radicaux cyclohexadiinyles muonts lorsqu'on fait riagir des atomes de muonium avec le benzkne, dans des conditions semblables. I1 semble que, dans un environnement micellaire, la riaction d'addition sur l'acitone est dipassi par une autre riaction plus rapide. On prisente des rLsultats confortant cette interpretation plut6t que celle faisant appel h une inhibition du radical ou h un diplacement du spectre de risonance de croisement au niveau du muon avec une liaison hydrogkne (muonium); toutefois, on observe des diplacements pour les spectres de ce radical dans des solvants purs de constantes diilectriques fort diffirentes. On suggkre que la riaction d'<(enlkvementn des muonium se produit dans des micelles en raison des effets de rehaussement induit par les micelles qui ont it6 observis antirieurement dans ce type de riaction. Les donnies sont en accord avec une constante de vitesse, pour la riaction d'enlkvement du muonium avec l'acitone dans les micelles, qui serait supirieure h 6 x loX M-' s-I.

show abstract

“…The simplicity of the spectrum is remarkable and it should be possible to study the behaviour of muonated radicals on surfaces. In order to measure the other nuclear hyperfme couplings one has to resort to the recently proposed [51] and developed [52,53] …”

Section: Matrix-endormentioning

confidence: 99%

“…On the other hand, it is difficult to obtain an ENDOR response from weakly interacting nuclei with low gyromagnetic ratios due to difficulties in saturating the NMR transitions. Likewise it is difficult to measure weak nuclear hyperfine frequencies in /¿SR [53]. However, the timing resolution is much better than in ESEM and muon hyperfine frequencies of > 4 GHz have been measured [56].…”

Section: Comparisonmentioning

confidence: 99%

Modern EPR-Related Methods in Surface Science and Heterogeneous Catalysis*

Heming¹

1987

Zeitschrift Für Physikalische Chemie

View full text Add to dashboard Cite

Detection of muonated free radicals through the effects of avoided level crossing. Theory and analysis of spectra

Cited by 87 publications

References 10 publications

Surface Dynamics of the Cyclohexadienyl Radical Adsorbed on Silica Gel Investigated Using Avoided Level-Crossing Muon Spin Resonance

Surface Dynamics of the Cyclohexadienyl Radical Adsorbed on Silica Gel Investigated Using Avoided Level-Crossing Muon Spin Resonance

Micelle-induced change of mechanism in the reaction of muonium with acetone

Modern EPR-Related Methods in Surface Science and Heterogeneous Catalysis*

Contact Info

Product

Resources

About