@article {1515,
	title = {Termolecular kinetics for the Mu+CO+M recombination reaction: A unique test of quantum rate theory},
	journal = {Journal of Chemical Physics},
	volume = {125},
	number = {1},
	year = {2006},
	note = {ISI Document Delivery No.: 061CTTimes Cited: 0Cited Reference Count: 66Pan, James J. Arseneau, Donald J. Senba, Masayoshi Garner, David M. Fleming, Donald G. Xie, Tiao Bowman, Joel M.},
	month = {Jul},
	pages = {13},
	type = {Article},
	abstract = {The room-temperature termolecular rate constants, k(0), for the Mu+CO+M reversible arrow MuCO+M (M=He, N-2, Ar) recombination reaction have been measured by the mu SR technique, and are reported for moderator gas pressures of up to similar to 200 bar (densities less than or similar to 0.4x10(22) molec cm(-3)). The experimental relaxation rates reveal an unusual signature, in being dominated by the electron spin-rotation interaction in the MuCO center dot radical that is formed in the addition step. In N-2 moderator, k(0)=1.2 +/- 0.1x10(-34) cm(6) s(-1), only about 30\% higher than found in Ar or He. The experimental results are compared with theoretical calculations carried out on the Werner-Keller-Schinke (WKS) surface [Keller , J. Chem. Phys. 105, 4983 (1996)], within the framework of the isolated resonance model (IRM). The positions and lifetimes of resonance states are obtained by solving the complex Hamiltonian for the nonrotating MuCO system, using an L-2 method, with an absorbing potential in the asymptotic region. Accurate values of the vibrational bound and resonance states of MuCO reveal unprecedented isotope effects in comparisons with HCO, due to the remarkable effect of replacing H by the very light Mu atom (m(Mu)approximate to 1/9m(H)). Due to its pronounced zero-point energy shift, there are only two (J=0) bound states in MuCO. Contributions from nonzero J states to the termolecular rate constants are evaluated through the J-shifting approximation, with rotational constants evaluated at the potential minimum. The value of the important A constant (181 cm(-1)) used in this approximation was supported by accurate J=K=1 calculations, from which A=180 cm(-1) was obtained by numerical evaluation. The calculations presented here, with a "weak collision factor" beta(c)=0.001, indicative of the very sparse density of MuCO states, give a very good account of both the magnitude and pressure dependence of the experimental rates, but only when the fact that the two initially bound (J=0) states become resonances for J > 0 is taken into account. This is the first time in IRM calculations of atom-molecule recombination reactions where J not equal 0 states have proven to be so important, thus providing a truly unique test of quantum rate theory. (c) 2006 American Institute of Physics.},
	keywords = {ADDITION-REACTIONS, DISSOCIATION DYNAMICS, FIELD-DEPENDENCE, GAS-PHASE, RATE-CONSTANT, RESOLUTION SPECTROSCOPIC DATA, RESONANCE ENERGIES, SPIN RELAXATION, thermal, THERMODYNAMIC PROPERTIES, UNIMOLECULAR, VIBRATIONALLY EXCITED DCO((X)OVER-TILDE(2)A{\textquoteright})},
	isbn = {0021-9606},
	url = {<Go to ISI>://000238849500019},
	author = {Pan, J. J. and Arseneau, D. J. and Senba, M. and Garner, D. M. and Fleming, Donald G. and Xie, T. and Bowman, J. M.}
}
@article {1141,
	title = {Muon implantation in inert gases studied by radio frequency spectroscopy},
	journal = {Journal of Physics B-Atomic Molecular and Optical Physics},
	volume = {38},
	number = {1},
	year = {2005},
	note = {ISI Document Delivery No.: 898AETimes Cited: 1Cited Reference Count: 51},
	month = {Jan},
	pages = {119-134},
	type = {Article},
	abstract = {Diamagnetic and muonium (Mu) fractions formed in low-pressure inert gases, by energetic muon implantation, have been studied using the technique of time-delayed radio frequency muon spin resonance (RF-muSR). Results obtained establish the validity of the long-held view that formation of these species is due only to prompt processes, and in turn confirms that the diamagnetic environment is due to a muon molecular ion, MMu(+), and not a bare mu(+). In addition, polarization fractions for the diamagnetic and Mu environments have been determined at different pressures, thereby complementing earlier data, and demonstrating that the RF-muSR technique provides polarization fractions in good accord with those obtained using conventional transverse-field muon spin resonance measurements.},
	keywords = {ADDITION-REACTIONS, CHARGE-EXCHANGE COLLISIONS, COMPETING PROCESSES, ELECTRON-SPIN EXCHANGE, MOLECULAR-IONS, NOBLE-GASES, POSITIVE MUONS, RESONANCE, SLOWING-DOWN, SUPERCRITICAL WATER},
	isbn = {0953-4075},
	url = {<Go to ISI>://000227047200016},
	author = {Johnson, C. and Cottrell, S. P. and Ghandi, K. and Fleming, Donald G.}
}
@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 = {<Go to ISI>://A1997YF25100014},
	author = {Pan, J. J. and Arseneau, D. J. and Senba, M. and Shelly, M. and Fleming, Donald G.}
}
@article {3664,
	title = {Spin relaxation of muonium-substituted ethyl radicals (MuCH(2)CH(2)) in the gas phase},
	journal = {Journal of Chemical Physics},
	volume = {105},
	number = {17},
	year = {1996},
	note = {ISI Document Delivery No.: VP288Times Cited: 20Cited Reference Count: 84},
	month = {Nov},
	pages = {7517-7535},
	type = {Article},
	abstract = {The spin relaxation of the muonium-substituted ethyl radical (MuCH(2)CH(2)) and its deuterated analog (MuCD(2)CD(2)) has been studied in the gas phase in both transverse and longitudinal magnetic fields spanning the range similar to 0.5-35 kG, over a pressure range from similar to 1-16 atm at ambient temperature. The Mu(13)CH(2)(13)CH(2) radical has also been investigated, at 2.7 atm. For comparison, some data is also reported for the MuCH(2)C(CH3)(2) (Mu-t-butyl) radical at a pressure of 2.6 atm. This experiment establishes the importance of the mu SR technique in studying spin relaxation phenomena of polyatomic radicals in the gas phase, where equivalent ESR data is sparse or nonexistent. Both T-1 (longitudinal) and T-2 (transverse) mu SR relaxation rates are reported and interpreted with a phenomenological model. Relaxation results from fluctuating terms in the spin Hamiltonian, inducing transitions between the eigenstates assumed from an isotropic hyperfine interaction. Low-field relaxation is primarily due to the electron, via both the nuclear hyperfine (S . A . I) and the spin rotation interactions (S . J), communicated to the muon via the isotropic muon-electron hyperfine interaction. At the highest fields, direct spin flips of the muon become important, due to fluctuations in the anisotropic part of the muon-electron hyperfine interaction. In the intermediate held region a muon-electron {\textquoteright}{\textquoteright}flip-flop{\textquoteright}{\textquoteright} relaxation mechanism dominates, due partly to the anisotropic hyperfine interaction and partly to modulation of the isotropic muon-electron hyperfine coupling. In the case of the T-2 rates, electron relaxation mechanisms dominate over a much wider field range than for the T-1 rates, and inhomogeneous line broadening also contributes. The fluctuations that induce both the T-1 and T-2 relaxation rates are described by a single correlation time, tau(c), inversely proportional to the pressure. An effective spin-reorientation cross section is deduced from this pressure dependence, sigma(J) similar to 100+/-20 Angstrom(2), for all topically substituted ethyl radicals. This is similar to the geometrical cross section, but about a factor of 4 larger than values of sigma(J) found for similar-sized diamagnetic molecules by gas phase NMR, primarily reflecting the longer range of the electron-induced intermolecular potential. (C) 1996 American Institute of Physics.},
	keywords = {ADDITION-REACTIONS, DYNAMICS, EXCHANGE, HYPERFINE COUPLING-CONSTANTS, INTERNAL-ROTATION, LATTICE RELAXATION, LEVEL-CROSSING, MAGNETIC-RESONANCE, MUONATED RADICALS, ORGANIC FREE-RADICALS, SPECTROSCOPY},
	isbn = {0021-9606},
	url = {<Go to ISI>://A1996VP28800027},
	author = {Fleming, Donald G. and Pan, J. J. and Senba, M. and Arseneau, D. J. and Kiefl, R. F. and Shelley, M. Y. and Cox, S. F. J. and Percival, P. W. and Brodovitch, J. C.}
}
@article {3185,
	title = {INTRAMOLECULAR SELECTIVITY OF MUONIUM TOWARDS CHLORINATED AROMATIC-COMPOUNDS},
	journal = {Hyperfine Interactions},
	volume = {87},
	number = {1-4},
	year = {1994},
	note = {ISI Document Delivery No.: PA118Times Cited: 0Cited Reference Count: 166th International Conference on Muon Spin Rotation/Relaxation/ResonanceMAY 31-JUN 11, 1993MAUI, HI},
	pages = {947-952},
	type = {Proceedings Paper},
	abstract = {Muon resonance studies show that muonium atoms (Mu) in ethanol add selectively to certain C-sites of aromatic compounds containing -Cl and -OH substituents. The sites chosen seem to be those carrying the lowest electron density. This helps to characterize Mu as a nucleophile in addition reactions and, in this respect, Mu differs from ordinary H-atoms. The study shows no apparent inter-molecular selectivity between a pair of aromatic solutes in an equimolar mixture, but strong intra-molecular selectivity in an ether composed of those two aromatic rings. This difference between intra- and inter-molecular selectivity is interpreted as kinetic in origin - arising from the {\textquoteright}caging effect{\textquoteright} of the solvent and peculiar to reactions close to the diffusion-controlled limit.},
	keywords = {ADDITION-REACTIONS, AQUEOUS-SOLUTIONS, BENZOIC-ACID, HYDROGEN ISOTOPES, LEVEL-CROSSING RESONANCE, Pyrazine, WATER},
	isbn = {0304-3843},
	url = {<Go to ISI>://A1994PA11800018},
	author = {Venkateswaran, K. and Stadlbauer, J. M. and Laing, M. E. and Klugkist, J. and Chong, D. P. and Porter, G. B. and Walker, D. C.}
}
@article {2889,
	title = {MUONIUM ATOM SPIN-EXCHANGE WITH ALKALI-METAL VAPORS - MU+CS},
	journal = {Physical Review A},
	volume = {48},
	number = {2},
	year = {1993},
	note = {ISI Document Delivery No.: LQ990Times Cited: 15Cited Reference Count: 77},
	month = {Aug},
	pages = {1218-1226},
	type = {Article},
	abstract = {The thermally averaged total electron spin-flip cross sections (sigma(SF)) for Mu-Cs have been measured in a 2 atm N2 moderator at 543, 566, and 643 K using the muon-spin-rotation technique. Within an overall experimental error of +/-15\%, the measured cross sections can be taken as temperature independent, sigma(SF)=39.7+/-6.0 X 10(-16) cm2, though there may be a trend to decreased values at the lower temperatures. This average value is considerably lower than either the early calculated results of Dalgarno and Rudge [Proc. R. Soc. London Ser. A 286, 519 (1965)] or the more recent ones of Cole and Olson [Phys. Rev. A 31, 2137 (1985)] for the corresponding H-Cs collisions, indicating a dramatic isotope effect.},
	keywords = {ADDITION-REACTIONS, COLLISIONS, CROSS-SECTIONS, ENERGIES, HYDROGEN-ATOMS, LOW-PRESSURE GASES, MU-SR, RATE CONSTANTS, relaxation, SCATTERING},
	isbn = {1050-2947},
	url = {<Go to ISI>://A1993LQ99000046},
	author = {Pan, J. J. and Senba, M. and Arseneau, D. J. and Kempton, J. R. and Fleming, Donald G. and Baer, S. and Gonzalez, A. C. and Snooks, R.}
}
@article {7172,
	title = {KINETIC ISOTOPE EFFECTS IN GAS-PHASE MUONIUM REACTIONS},
	journal = {Acs Symposium Series},
	volume = {502},
	year = {1992},
	note = {ISI Document Delivery No.: JY550Times Cited: 16Cited Reference Count: 101},
	pages = {111-137},
	type = {Review},
	abstract = {The study of the reaction dynamics of muonium (Mu), an ultralight isotope of hydrogen ((m)Mu/(m)H almost-equal-to 1/9), provides a sensitive measure of mass effects in chemical reactions. The remarkable mass difference between Mu and the other hydrogen isotopes produces large kinetic isotope effects, providing a rigorous test of calculated potential energy surfaces (PES) and reaction rate theories. The low Mu mass also necessitates careful consideration of quantum effects, i.e. tunneling in the reaction coordinate. A review of recent results in gas phase Mu chemistry is presented, including comparison with relevant H chemistry and calculated PESs, where available. The magnitude and direction of the kinetic isotope effect is shown to be a sensitive function of the PES, particularly the height and position of the saddle point.},
	keywords = {+ HBR(DBR) ABSTRACTION, ACTION, ADDITION-REACTIONS, CALCULATIONS, CHARGE-EXCHANGE, COLLISIONS, LOW-TEMPERATURES, POTENTIAL-ENERGY SURFACES, PRESSURE-DEPENDENCE, RESONANCE, THERMAL RATE CONSTANTS, TRANSITION-STATE THEORY, TUNNELING PATHS},
	isbn = {0097-6156},
	url = {<Go to ISI>://A1992JY55000008},
	author = {Baer, S. and Fleming, Donald G. and Arseneau, D. and Senba, M. and Gonzalez, A.}
}
