The addition of an organic acid to the manganese(V)-oxo corrole complex (tpfc)MnV(O) (tpfc = 5,10,15-tris(pentafluorophenyl)corrole) induces valence tautomerization resulting in the formation of ...(tpfc+•)MnIV(OH) in acetonitrile at 298 K. The corrole radical cation manganese(IV) hydroxo complex has been fully characterized by EPR, 1H NMR, and UV–vis spectroscopy. The reactivity of the valence tautomer (tpfc+•)MnIV(OH) is compared to that of (tpfc)MnV(O) in three reaction types: hydrogen atom transfer (HAT), electron transfer (ET), and oxygen atom transfer (OAT). (tpfc+•)MnIV(OH) shows a dramatic 5 orders of magnitude enhancement in the rate of ET but surprisingly does not undergo OAT with PhSMe. The high-valent (tpfc)MnV(O) complex is moderately more reactive toward HAT with substituted phenol and shows superior activity in OAT.
Rate constants of electron self-exchange of high-valent oxo and imido complexes of chromium(V/IV) corrole have been determined in acetonitrile and toluene at various temperatures by electron ...paramagnetic resonance (EPR) line width variation of the EPR spectra. The observed activation enthalpies (ΔH obs ⧧) of electron self-exchange of chromium(V)–oxo and –imido corrole with the corresponding chromium(IV) complexes are zero in toluene, whereas the ΔH obs ⧧ values are slightly positive in acetonitrile. Such activationless electron self-exchange transfer resulted in extremely fast electron-transfer reactions of chromium(V)–oxo and −imido corrole in sharp contrast with slow electron-transfer reactions of other high-valent metal–oxo and −imido complexes.
The Physics of the B Factories Bevan, Adrian; Golob, Bostjan; Mannel, Thomas ...
The European physical journal. C, Particles and fields,
March 2015, Letnik:
74, Številka:
11
eBook, Journal Article
Recenzirano
Odprti dostop
This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related ...issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C.
Dark sectors charged under a new Abelian interaction have recently received much attention in the context of dark matter models. These models introduce a light new mediator, the so-called dark photon ...(A^{'}), connecting the dark sector to the standard model. We present a search for a dark photon in the reaction e^{+}e^{-}→γA^{'}, A^{'}→e^{+}e^{-}, μ^{+}μ^{-} using 514 fb^{-1} of data collected with the BABAR detector. We observe no statistically significant deviations from the standard model predictions, and we set 90% confidence level upper limits on the mixing strength between the photon and dark photon at the level of 10^{-4}-10^{-3} for dark photon masses in the range 0.02-10.2 GeV. We further constrain the range of the parameter space favored by interpretations of the discrepancy between the calculated and measured anomalous magnetic moment of the muon.
The kinetics of formation of the valence tautomers (tpfc⋅)MnIV(O−LA)n+ where LA=ZnII, CaII, ScIII, YbIII, B(C6F5)3, and trifluoroacetic acid (TFA); tpfc=5,10,15‐tris(pentafluorophenyl) corrole from ...(tpfc)MnV(O) were followed by UV/Vis spectroscopy, giving second‐order rate constants ranging over five orders of magnitude from 10−2 for Ca to 103 m−1 s−1 for Sc. Hydrogen atom transfer (HAT) rates from 2,4‐di‐tert‐butyl phenol (2,4‐DTBP) to the various Lewis acid valence tautomers of manganese oxo corrole complexes were evaluated and compared. For LA=TFA, ScIII, or YbIII, the rate constants of HAT were comparable to unactivated (tpfc)MnV(O). However, with LA=B(C6F5)3, ZnII, and CaII, 6‐, 21‐, and 31‐fold rate enhancements were observed, respectively. Remarkably, (tpfc⋅)MnIV(OCa)2+ gave the most enhancement despite its rate of formation being the slowest. Comparisons of HAT rate constants among the various Lewis acid tautomers revealed that both size and charge are important. This study underscores how valence may affect the reactivity of high‐valent manganese‐oxo compounds and sheds light on nature's choice of Ca in the activation of Mn‐oxo in the oxygen‐evolving complex.
HATs off to you! Acid‐induced valence tautomerism to form a Mn corrole with π‐radical ligand character by using a variety of Lewis acids ZnII, CaII, ScIII, YbIII, B(C6F5)3, and TFA proceeds with rates that are highly dependent on the Lewis acid. The kinetics of hydrogen atom transfer (HAT) shows an enhancement for Zn and Ca. This study provides a fundamental understanding of how Lewis acids and valence tautomerization affect HAT reactivity.
Chloride oxyanions are of interest because of their use as disinfectants and concerns over their accumulation in the environment. A water‐soluble manganese porphyrin catalyzes the dismutation of ...chlorite (ClO2−) to chlorine dioxide (ClO2) through a series of electron‐ and atom‐transfer reactions. A high‐valent manganese(IV) oxo species is observed and the ClO2 product inhibits the reaction.
The Physics of the B Factories Golob, Bostjan; Mannel, Thomas; Bevan, Adrian
The European physical journal. C, Particles and fields,
March 2015, Letnik:
74, Številka:
11
eBook, Journal Article
A precise measurement of the cross section for the process e + e − → K + K − ( γ ) from threshold to an energy of 5 GeV is obtained with the initial-state radiation (ISR) method using 232 fb − 1 ...of data collected with the BABAR detector at e + e − center-of-mass energies near 10.6 GeV. The measurement uses the effective ISR luminosity determined from the e + e − → μ + μ − ( γ ) γ ISR process with the same data set. The corresponding lowest-order contribution to the hadronic vacuum polarization term in the muon magnetic anomaly is found to be a K K , LO μ = ( 22.93 ± 0.18 stat ± 0.22 syst ) × 10 − 10 . The charged kaon form factor is extracted and compared to previous results. Its magnitude at large energy significantly exceeds the asymptotic QCD prediction, while the measured slope is consistent with the prediction.
We measure the mass difference Δm0 between the D*(2010)+ and the D0 and the natural linewidth Γ of the transition D*(2010)+ → D0π+. The data were recorded with the BABAR detector at center-of-mass ...energies at and near the Υ(4S) resonance, and correspond to an integrated luminosity of approximately 477 fb(-1). The D0 is reconstructed in the decay modes D0 → K- π+ and D0 → K- π+ π- π+. For the decay mode D0 → K- π+ we obtain Γ = (83.4±1.7±1.5) keV and Δm0 = (145425.6±0.6±1.7) keV, corrected where the quoted errors are statistical and systematic, respectively. For the D0 → K- π+ π- π+ mode we obtain Γ = (83.2±1.5±2.6) keV and Δm0 = (145426.6±0.5±1.9) keV. corrected The combined measurements yield Γ = (83.3±1.2±1.4) keV and Δm0 = (145425.9±0.4±1.7) keV; the width is a factor of approximately 12 times more precise than the previous value, while the mass difference is a factor of approximately 6 times more precise.
We present results of a search for CP violation in B0- B0 mixing with the BABAR detector. We select a sample of B0→D*- Xℓ+ ν decays with a partial reconstruction method and use kaon tagging to assess ...the flavor of the other B meson in the event. We determine the CP violating asymmetry ACP≡N(B0B0)-N(B0B0)/N(B0B0)+N(B0B0)=(0.06±0.17(-0.32)(+0.38))%, corresponding to ΔCP=1-|q/p|=(0.29±0.84(-1.61)(+1.88))×10(-3).
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