Muonium reactions

By now most of the studies were carried out using nanosecond pulse radiolysis techniques coupled with spectroscopic detection method, only a few were reported to use muonium reactions, ° steady state (7 )radiolysis, laser phtolysis, and picosecond pulse radiolysis. Since conventional pulse radiolysis techniques are well known, here we just briefly introduce the high temperature high pressure (HTHP)... 

The reactions of A-phenyl a-r-butyl nitrone (PEN) with maleimides, maleic anhydride, and diethyl maleate have been studied by EPR and two types of spin adduct detected. They arise from the reductive addition of PEN to the alkenes and the degradation product of DEN (2-methyl-2-nitropropane). The deuterium and muonium kinetic isotope effects for the addition of the hydrogen atom to a variety of alkenes have been determined experimentally and theoretically. ... 

Muonium chemistry gaseous phase, 28 119-120 liquid mixtures, 28 120-122 radical formation and reactions, 28 122-130 Mushrooms, vanadium in, 35 96-97 Mutagenesis, site-directed, flavocytochrome bj, 36 289-290 MXj-... 

Kinetic data for the reactions of diazodiphenylmethane in 10 different alcohols with 2-(4-phenyl substituted)cyclohex-l-enylcarboxylic acids (75) were correlated using the extended Hammett equation.68 Reaction of the species (76)-(78) with the light radioactive H isotope, the muonium atom, has been studied.69 The largest primary kinetic isotope effects ever reported (ca 850) are seen in this work for the addition of muonium to one of the C=0 groups. 

Other research in tire area of addition reactions onto unsaturated carbon-carbon bonds has included measurement of the rate coefficients for tire addition of NO3 to chloro- and trichloro-ethene,147 relative rate measurement for N03 addition to isoprene,148 TF-/(SR-measured muonium addition to vinyl aromatics12 and EPR studied addition of radical (65) to alkenes.150 In this latter study a linear dependence of the rate constant of addition with tire donor/acceptor properties of the alkene partner was highlighted. 

Cl (12), I (13), N (14), Si (9), other polyvalent atoms (15), and of muonium (16). Reviews have also been published on the reactions of recoil atoms with arenes (17), (halo)ethylenes (18), and (halo)-methanes (19). The capture of ir in hydrogenated species is sometimes considered as a part of recoil chemistry (20), and so also are reactions of species formed after decay of multiply labeled (T, 14C) molecules (21-23), for example,... 

S-Matrix Propagation along Delves Radial Coordinate. J. Manz and J. Romelt, Chem. Phys. Lett., 77, 172 (1981). Dissociative Collinear Reactions Evaluated by S-Matrix Propagation along Delves Radial Coordinate. J. Manz and J. Romelt, Chem. Phys. Lett. 81,179 (1981). On the Collinear 1+ HI and 1+ Mul Reactions. (Here Mu represents a muonium isotopic variant.)... 

Metastable muonium atoms in the 2s state have been produced with a beam foil technique at LAMPF and at the Tri University Meson Physics Facility (TRI-UMF) at Vancouver, Canada. Only moderate numbers of atoms could be obtained. The velocity resonance nature of the electron transfer reaction results in a muonium beam at keV energies. Very difficult and challenging experiments using electromagnetic transitions in excited states, particularly the 2 Si/2 2 Pi/2 classical Lamb shift and 2 Si/2-2 P3/2 splitting could be induced with microwaves. However, the achieved experimental accuracy at the 1.5 % level [18,19,20], does not represent a severe test of theory yet. 

Numerous applications of [Cr(NH3)6]3+ and its derivatives to mechanistic studies of conventional or photo-assisted ligand-exchange reactions have been extensively reviewed.7,270-276 Among other common Cr111 complexes, [Cr(NH3)6]3+ has been used for the studies of reactivities of muonium and positronium atoms in aqueous solutions.313-315 Several computational methods, including DFT calculations,316 a combination of molecular mechanics and angular overlap model calculations, or vibrational analysis have been used for the prediction and interpretation of electronic spectra and photochemical properties of [Cr(NH3)6]3+. 

Muonium has been observed in pure hydrocarbons ( ), alcohols (, 7 ), and water ( ). Because Mu reacts slowly with these pure liquids, giving observable reaction lifetimes of Mu up to 4us, they can be used as solvents to study various solutes of interest. As the free triplet Mu atom reacts with the solute its observed precession frequency is damped and a decay constant, X can be obtained. The concentration dependence of the decay constant provides second order chemical rate constants for Mu addition, abstraction, spin conversion, and oxidation-reduction reactions. When analogous hydrogen atom rate constants are available the kinetic isotope effect can also be calculated. 

Muonium is useful as a hydrogen-like probe to study the atomic and radical reactions of hydrogen because Mu s reaction decay constant is directly observable, while most hydrogen atom data come from measured relative rate constants. The more we know of the reactions of hydrogen, the simplest and most abundant element in the universe, the sooner we will be better able to understand more complex atoms and their reactions. 

Reactions of epithermal p and epithermal Mu also induce changes in the chemical state of p and, after thermalization, p will emerge incorporated either in diamagnetic states (with a fraction h), muonium (fraction m) or Mu-substituted free radicals (fraction r). They may further change their chemic states either by thermal reactions or, in the condensed phases, by intra-spur reactions. 

In the next section, we present several applications of the reduced dimensionality theory just reviewed. The applications are to the reaction of muonium+H2 resonances in H+H2 and the reactions 0( P)+H, and HD where comparisons with experiment are given. 

Schatz has recently performed three-dimensional centrif al sudden (CS) calculations of the reaction of muonium with H2 (also see his using the ab imitio LSTH potential energy... 

In muonium chemistry, hot muonium (Mu ) has been used for its similarity to hot hydrogen. Senba et al. (2000) studied hot atom reaction yield in Mu + H2, and T + H2 from quasiclassical trajectory cross sections on the Liu-Siegbahn-Truhler-Horowitz surface. Other examples are described in Chap. 28 on Exotic Atoms and Muonium in this Volume. 

In materials containing molecules with unsaturated centers, muonium that is formed at the end of the radiation track can react chemically to give radical species. The simplest case of a reaction with a double bond is illustrated in Figure 7.1 where the addition of muonium opens the carbon-carbon double bond to give a C-Mu bond and a radical electron. 

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