@article {1306, title = {Orbital-overlap control of the reactivity of a bicyclic 1-hydroxy-1,4-biradical}, journal = {Angewandte Chemie-International Edition}, volume = {44}, number = {32}, year = {2005}, note = {ISI Document Delivery No.: 957JYTimes Cited: 13Cited Reference Count: 23}, pages = {5087-5089}, type = {Article}, keywords = {4-BIRADICALS, ASYMMETRIC INDUCTION, asymmetric synthesis, CHIRAL AUXILIARY APPROACH, CONFORMATIONAL MEMORY, ORGANIC-PHOTOCHEMISTRY, PHOTOCHEMICAL-SYNTHESIS, PHOTOCHEMISTRY, radicals, solid-state reactions, STATE REACTIVITY, STEREOSELECTIVITY, structure-activity relationships, TRIPLET 1}, isbn = {1433-7851}, url = {://000231367300019}, author = {Yang, C. and Xia, W. J. and Scheffer, J. R. and Botoshansky, M. and Kaftory, M.} } @article {5226, title = {Reaction of human myoglobin and peroxynitrite: Characterizing biomarkers for myoglobin-derived oxidative stress}, journal = {Biochemical and Biophysical Research Communications}, volume = {286}, number = {2}, year = {2001}, note = {ISI Document Delivery No.: 465TNTimes Cited: 11Cited Reference Count: 32}, month = {Aug}, pages = {352-356}, type = {Article}, abstract = {Mixtures of human myoglobin (Mb) (or the Y103F variant of human Mb), authentic peroxynitrite (ONOO-, ONOO-:protein 2 mol/mol), and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) gave radicals adducts at cysteine-110 (DMPO-C110) that are detected directly by electron paramagnetic magnetic spectroscopy (EPR). DMPO-C110 was detected exclusively over a range of DMPO concentrations (DMPO:protein ratios 25-100 mol/mol). Treatment of human Mb (or Y103F Mb) with the ONOO- generator 5-amino-3-(4-morpholinyl)-1,2,3-oxadiazolium (SIN-1) chloride (ONOO-: protein 5 mol/mol) yielded a cross-linked Mb dimer as judged by SDS-PAGE analyses. Addition of DMPO or carbonate effectively eliminated the cross-linked product. Mass analyses of samples containing human Mb (or Y103F Mb), carbonate, and ONOO- indicated that nitration occurs exclusively at Y103. Thus, reaction of human Mb and ONOO- yields specific products that depend on the presence or absence of physiological concentrations of carbonate. These products may serve as biomarkers for the participation of Mb-derived radicals in the oxidative damage associated with myocardial reperfusion injury. (C) 2001 Academic Press.}, keywords = {ARRHYTHMIAS, free radical, GENERATION, HYDROGEN-PEROXIDE, ischaemia reperfusion injury, MECHANISMS, MYOGLOBIN, NITRATION, NITRIC-OXIDE, nitro-tyrosine, peroxynitrite, protein-thiyl radical, radicals, REPERFUSION INJURY, SITE-DIRECTED MUTAGENESIS, SUPEROXIDE, SYSTEMS}, isbn = {0006-291X}, url = {://000170606200020}, author = {Witting, P. K. and Mauk, A. G. and Douglas, D. J. and Stocker, R.} } @article {4723, title = {The rate constant for Mu+O-2 addition in competition with rapid spin exchange}, journal = {Physica B-Condensed Matter}, volume = {289}, year = {2000}, note = {ISI Document Delivery No.: 330GBTimes Cited: 3Cited Reference Count: 158th International Conference on Muon Spin Rotation, Relaxation and ResonanceAUG 30-SEP 03, 1999LES DIABLERETS, SWITZERLANDEuropean Phys Soc, Paul Scherrer Inst, Eidgenoss Tech Hochschule, Univ Zurich, European Sci Fdn, Swiss Natl Sci Fdn, Neue Aargauer Bank, Sauerstoffwerk Lenzburg AG, Hamamatsu Photon, EG \& G Berthold GmbH \& Co KG, Prophysik AG, Kroger \& Co, Wenger SA, Alcatel Hochvakuum Tech GmbH, Sunrise AG, Dramer AG, Automobil \& Motoren AG}, month = {Aug}, pages = {503-506}, type = {Proceedings Paper}, abstract = {The rate of the addition reaction H + O-2 {\textendash}> HO2, is measured at high O-2 concentrations (up to 40 bar of O-2 at room temperature) through its competition with rapid spin exchange, to give k(ch)(0) = 8.7 +/- 0.8 x 10(-3)3 cm(6)s(-1) ch (C) 2000 Published by Elsevier Science B.V. All rights reserved.}, keywords = {ELECTRON-SPIN EXCHANGE, GAS-PHASE, muonium, muonium oxygen recombination kinetics spin exchange, radicals, relaxation}, isbn = {0921-4526}, url = {://000087953500130}, author = {Arseneau, D. J. and Senba, M. and Pan, J. J. and Fleming, Donald G.} } @article {4423, title = {Theory of muon spin relaxation of Mu+CO}, journal = {Physical Review A}, volume = {58}, number = {6}, year = {1998}, note = {ISI Document Delivery No.: 145CDTimes Cited: 5Cited Reference Count: 35}, month = {Dec}, pages = {4431-4446}, type = {Article}, abstract = {In previous papers [Phys. Rev. A 50, 4743 (1994); 54, 4815 (1996)] a theoretical description of the signals associated with the muon spin relaxation of simple muonated gaseous radicals has been presented. These gaseous radicals were assumed to have been formed during the slowing down process of the muons in the gaseous target and assumed to be stable chemical species at the initial observation time. The observed signals were attributed to these stable radicals. In this paper the theoretical description is extended to include situations where the radicals are formed in slow processes as opposed to fast processes with the assumption that the muon exists as muonium at the initial observation time. This muonium then reacts for the time duration of the experiment, which is limited by the muon{\textquoteright}s lifetime. The theoretical treatment is based on an operator expansion of the spin density operators for muonium and for the molecular radicals whose time dependences are described by a set of coupled linearized quantum kinetic equations. Relaxation of the signals is due to two effects, namely, the chemical reactions themselves and the collisions that reorient the molecular radical{\textquoteright}s rotational angular momentum. This affects the muon{\textquoteright}s spin via intramolecular couplings between the muon{\textquoteright}s spin, the radical{\textquoteright}s free-electron spin, and the radical{\textquoteright}s rotational angular momentum. The coefficients of the radical{\textquoteright}s spin Hamiltonian, the collisional reorientation lifetimes (cross sections), and the chemical reaction rates may be used as fitting parameters to describe the experimental signals. These could also be calculated from first principles. [S1050-2947(98)00212-1].}, keywords = {EXCHANGE, GAS-PHASE, IRREDUCIBLE CARTESIAN TENSORS, O-2, radicals, REACTION-KINETICS}, isbn = {1050-2947}, url = {://000077352700025}, author = {Turner, R. E. and Snider, R. F.} } @article {4135, title = {Fast muonium reactions in solution: An electron spin exchange interaction with Cr(NCS)(6)(3-) in water and reaction with iodine in organic solvents}, journal = {Journal of Physical Chemistry A}, volume = {101}, number = {26}, year = {1997}, note = {ISI Document Delivery No.: XG935Times Cited: 3Cited Reference Count: 34}, month = {Jun}, pages = {4741-4744}, type = {Article}, abstract = {Two reactions of muonium atoms close to the diffusion-controlled limit were analyzed as a function of solute size and solvent viscosity. With Cr(NCS)(6)(3-) as solute in water, the reaction is an electron spin-conversion process, and the observed rate is taken to be half of the actual encounter rate, because of the quantum mechanical statistical factor and the occurrence of multiple collisions due to the solvent cage effect. The encounter rate deduced is 6.2 x 10(10) M-1 s(-1), which implies a large cross section for the Cr complex. In a second series of experiments, the rate of reaction of muonium with I-2 was compared in water, methanol and n-heptane. The bimolecular rate constants determined are (1.7 +/- 0.3), (7.0 +/- 1.2), and (57 +/- 22) x 10(10) M-1 s(-1), respectively, in these three solvents. This similar to 30-fold change in rate is not matched by the change in the inverse of the solvents{\textquoteright} viscosities, which changed overall by a factor of only 2.4. It looks as if quantum tunneling dominates over classical diffusion in less polar media where muonium is unencumbered by solvent clathration.}, keywords = {AQUEOUS-SOLUTION, COMPLEXES, HYDROGEN-ATOMS, O-2, POSITRONIUM, radicals, relaxation, ROTATION}, isbn = {1089-5639}, url = {://A1997XG93500012}, author = {Stadlbauer, J. M. and Venkateswaran, K. and Porter, G. B. and Walker, D. C.} } @article {4146, title = {Investigation of the pure rotational spectrum of magnesium monobromide by Fourier transform microwave spectroscopy}, journal = {Journal of Chemical Physics}, volume = {107}, number = {23}, year = {1997}, note = {ISI Document Delivery No.: YK982Times Cited: 7Cited Reference Count: 39}, month = {Dec}, pages = {9835-9841}, type = {Article}, abstract = {The pure rotational spectrum of the free radical MgBr has been measured in its (2) Sigma(+) ground electronic state by Fourier transform microwave spectroscopy. Transitions have been observed for both (MgBr)-Mg-24-Br-79 and (MgBr)-Mg-24-Br-81 in the v = 0 and v = 1 vibrational states. Rotational and centrifugal distortion constants have been determined for each isotopomer in each vibrational state. Equilibrium rotational constants have been calculated and an accurate equilibrium bond length has been determined. Spin-rotation constants, for both the unpaired electron and the bromine nuclei, have been calculated along with magnetic and nuclear quadrupole hyperfine constants for the bromine nuclei. From these constants, the electronic structure of MgBr has been investigated and comparisons have been made to similar compounds. The unpaired electron spin density on the bromine nucleus has been found to be very small, suggesting that this is a very ionic compound. However, the Mg-Br bond has been found to have more covalent character than the bond in other alkaline earth monobromides. (C) 1997 American Institute of Physics. [S0021-9606(97)02046-1].}, keywords = {BAF, CABR, HYPERFINE-STRUCTURE, MGF, MILLIMETER-WAVE SPECTRUM, MOLECULAR-BEAM, PARAMETERS, radicals, RF DOUBLE-RESONANCE, SPECTROMETER}, isbn = {0021-9606}, url = {://A1997YK98200014}, author = {Walker, K. A. and Gerry, M. C. L.} } @article {4096, title = {Reaction kinetics of muonium with N2O in the gas phase}, journal = {Journal of Physical Chemistry A}, volume = {101}, number = {45}, year = {1997}, note = {ISI Document Delivery No.: YF251Times Cited: 6Cited Reference Count: 64}, month = {Nov}, pages = {8470-8479}, type = {Article}, abstract = {The thermal reaction Mu + N2O has been studied by the muon spin rotation (mu SR) technique at temperatures from 303 to 593 K and pressures up to 60 atm. The overall reaction rate coefficient depends on the N2O pressure quadratically in pure N2O and is proportional to both the N2O partial pressure and the total pressure in mixtures, confirming the theoretical prediction of Diau and Lin that the analogous H atom reaction proceeds through two channels in this temperature range, forming different products, MuN(2)O and MuO + N-2. The measured total rate coefficients are much larger than those reported by Marshall et al. for H(D) + N2O, indicating a dramatic kinetic isotope effect, which is mainly due to the enhanced quantum tunneling of the ultralight Mu atom. Even at room temperature (and low pressure), k(Mu)/k(H) approximate to 120, the largest yet seen in comparisons of gas-phase Mu and H reactivity at such relatively high temperatures. The addition reaction forming MuN(2)O (and by implication, HN2O) contributes significantly to the total reaction rate at higher pressures but with the thermal rate coefficient remaining in the termolecular regime even at the highest pressures measured.}, keywords = {ADDITION-REACTIONS, CHARGE-EXCHANGE, CHEMICAL-REACTION, H-ATOMS, HIGH-TEMPERATURE PHOTOCHEMISTRY, HYDROGEN-ATOMS, radicals, RATE CONSTANTS, SHOCK-TUBE, SPIN RELAXATION}, isbn = {1089-5639}, url = {://A1997YF25100014}, author = {Pan, J. J. and Arseneau, D. J. and Senba, M. and Shelly, M. and Fleming, Donald G.} } @article {3090, title = {ELECTRON-SPIN EXCHANGE-REACTIONS OF MUONIUM ATOMS WITH CHROMIUM(III) COMPLEXES - CONTRASTS WITH POSITRONIUM}, journal = {Journal of Physical Chemistry}, volume = {98}, number = {33}, year = {1994}, note = {ISI Document Delivery No.: PC619Times Cited: 7Cited Reference Count: 25}, month = {Aug}, pages = {8050-8052}, type = {Article}, abstract = {Muonium atoms were observed to undergo a fast reaction with several chromium(III) complexes in water, with rate constants in the neighborhood of 10(10) M(-1) s(-1). The reaction occurring is attributed to a simple electron-spin-exchange in muonium, catalyzed by the paramagnetic d(3) metal ions. There is a quantum mechanical statistical factor for this process of 62\% per collision, which becomes 50\% when multicollisional cage effects in solution are included, with the result that the observed rates are close to the diffusion-controlled limit for a muonium reaction in water. The implication is that nearly half of the encounters between muonium and a Cr complex result in electron spin exchange. These muonium rates are faster by a factor of similar to 5 than the corresponding reactions of positronium. They also show a different dependence on the nature of the ligands. These differences are attributed to positronium being larger and more polarizable than muonium, so that spin-spin coupling with the metal{\textquoteright}s d electrons is weaker and more sensitive to the nephelauxetic effect of the ligands in the case of positronium. The corresponding reactions involving ordinary H atoms are not available for comparison but presumably resemble muonium{\textquoteright}s.}, keywords = {radicals, RADIOLYSIS, relaxation}, isbn = {0022-3654}, url = {://A1994PC61900022}, author = {Lazzarini, E. and Stadlbauer, J. M. and Venkateswaran, K. and Gillis, H. A. and Porter, G. B. and Walker, D. C.} } @article {7007, title = {THE ANALYSIS OF MUONIUM HYPERFINE INTERACTION MEASUREMENTS OF THERMAL RATE CONSTANTS FOR ADDITION-REACTIONS}, journal = {Journal of Chemical Physics}, volume = {94}, number = {4}, year = {1991}, note = {ISI Document Delivery No.: EY070Times Cited: 15Cited Reference Count: 48}, month = {Feb}, pages = {2794-2806}, type = {Article}, abstract = {A new model is developed for the analysis of muon spin relaxation (mu-SR) measurements of muonium (Mu) reaction rates with other chemical species. The kinetics component of the model is specifically developed for addition reactions but can be extended to direct reactions. The polarization component of the model assumes that the adduct formed possesses a single, effective spin precession frequency. The complete model is solved to obtain an analytic expression for the mu-SR signal as a function of time. Both a time-ordered sequence method and a Boltzmann spin equation method give equivalent solutions. These solutions are analyzed under various kinetic conditions. It is concluded that the coefficient controlling the decay of the mu-SR signal is closely related to the adduct formation rate constant, i.e., the high pressure limit of the apparent bimolecular addition rate constant. In the most favorable case, the decay constant gives the adduct formation rate constant directly at all pressures of buffer gas.}, keywords = {CHARGE-EXCHANGE COLLISIONS, COMPETING PROCESSES, DEPENDENCE, HYDROGEN, KINETIC-EQUATIONS, LOW-PRESSURE GASES, MOLECULAR ION, radicals, SPIN-EXCHANGE, TEMPERATURE-RANGE}, isbn = {0021-9606}, url = {://A1991EY07000050}, author = {Duchovic, R. J. and Wagner, A. F. and Turner, R. E. and Garner, D. M. and Fleming, Donald G.} } @article {6889, title = {QUANTUM PHENOMENA AND SOLVENT EFFECTS ON ADDITION OF HYDROGEN ISOTOPES TO BENZENE AND TO DIMETHYLBUTADIENE}, journal = {Berichte Der Bunsen-Gesellschaft-Physical Chemistry Chemical Physics}, volume = {94}, number = {11}, year = {1990}, note = {ISI Document Delivery No.: EU906Times Cited: 18Cited Reference Count: 4189TH GENERAL ASSEMBLY OF THE DEUTSCHE-BUNSEN-GESELLSCHAFT-FUR-PHYSIKALISCHE-CHEMIE ( ON THE 65TH BIRTHDAY OF THEODOR ACKERMANN ) : CHEMICAL ELEMENTAL REACTIONSMAY 24-26, 1990TUBINGEN, FED REP GERDEUT BUNSEN GESELL PHYS CHEM}, month = {Nov}, pages = {1224-1230}, type = {Proceedings Paper}, abstract = {Rate constants have been measured for the reaction of the light hydrogen isotope muonium with benzene and 2,3-dimethylbutadiene-1,3 in the gas phase and in several solvents. Comparison with H atom data reveals (1) appreciable kinetic isotope effects, (2) a strong contribution of tunnelling for the activated reaction with benzene, (3) encounter controlled reaction for Mu addition to the diene, (4) a mass dependence of the diffusion constant of hydrogen isotopes in solution, and (5) an enhancement of the rate constant in solution over that in the gas phase by a factor, except for water, of the inverse Ostwald solubility coefficient for hydrogen. The isotope-dependent reduction of the solvent effect in water is tentatively ascribed to the dynamics of the clathrate-like structure when the hydrogen atom reacts.}, keywords = {ATOM, DIFFUSION, electron, ELEMENTARY REACTIONS, GASES, ISOTOPE EFFECTS, KINETICS, LIQUIDS, muonium, radicals, RATE CONSTANTS, solutions, WATER}, isbn = {0005-9021}, url = {://A1990EU90600008}, author = {Roduner, E. and Louwrier, P. W. F. and Brinkman, G. A. and Garner, D. M. and Reid, I. D. and Arseneau, D. J. and Senba, M. and Fleming, Donald G.} }