@article {4565,
	title = {Kinetic isotope effect in the gas-phase reaction of muonium with molecular oxygen},
	journal = {Journal of Physical Chemistry A},
	volume = {103},
	number = {13},
	year = {1999},
	note = {ISI Document Delivery No.: 184KQTimes Cited: 13Cited Reference Count: 101},
	month = {Apr},
	pages = {2076-2087},
	type = {Review},
	abstract = {The rate constant of the gas-phase addition reaction of the light hydrogen isotope muonium to molecular oxygen, Mn + O-2 {\textendash}> MuO(2), was measured over a range of temperatures from 115 to 463 K at a pressure of 2 bar and from 16 to 301 bar at room temperature, using N-2 as the moderator gas. The reaction remains in the termolecular regime over the entire pressure range. At room temperature, the average low-pressure limiting rate constant is k(ch)(0)(Mu) = (8.0 +/- 2.1) x 10(-33) cm(6) s(-1), a factor of almost 7 below the corresponding rate constant for the H + O-2 addition reaction, k(ch)(0)(H). In contrast to k(ch)(0)(H), which exhibits a clear negative temperature dependence, k(ch)(0)(MU) is essentially temperature independent. At room temperature, the kinetic isotope effect (KIE) is strongly pressure (density) dependent and is reversed at pressures near 300 bar. The kinetics are analyzed based on the statistical adiabatic channel model of Tree using a Morse potential, which works well in reproducing the overall KIE. The major factors governing the isotope effect are differences in the moment of inertia and density of vibrational states of the addition complex.},
	keywords = {ABSOLUTE RATE, CHARACTERIZATION, COLLISION RATE CONSTANTS, CONSTANTS, ELECTRON-SPIN-EXCHANGE, LOW-PRESSURES, POTENTIAL-ENERGY SURFACE, RATE COEFFICIENTS, THEORETICAL, THERMAL UNIMOLECULAR REACTIONS, TRAJECTORY CALCULATIONS, TRANSITION-STATE THEORY},
	isbn = {1089-5639},
	url = {<Go to ISI>://000079611700020},
	author = {Himmer, U. and Dilger, H. and Roduner, E. and Pan, J. J. and Arseneau, D. J. and Fleming, Donald G. and Senba, M.}
}
@article {3528,
	title = {THE THERMAL-REACTION RATE OF MUONIUM WITH METHANE (AND ETHANE) IN THE GAS-PHASE},
	journal = {Journal of Chemical Physics},
	volume = {102},
	number = {12},
	year = {1995},
	note = {ISI Document Delivery No.: QM507Times Cited: 12Cited Reference Count: 52},
	month = {Mar},
	pages = {4860-4869},
	type = {Article},
	keywords = {ABINITIO, ABSTRACTION, DYNAMICS, FLASH-PHOTOLYSIS, H-2 REVERSIBLE CH4+H, MU+D2, RATE CONSTANTS, REACTION-KINETICS, SURFACES, TRANSITION-STATE THEORY},
	isbn = {0021-9606},
	url = {<Go to ISI>://A1995QM50700015},
	author = {Snooks, R. and Arseneau, D. J. and Fleming, Donald G. and Senba, M. and Pan, J. J. and Shelley, M. and Baer, S.}
}
@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.}
}
@article {7248,
	title = {MUONIUM REACTION-KINETICS WITH THE HYDROGEN HALIDE GASES},
	journal = {Journal of Chemical Physics},
	volume = {97},
	number = {9},
	year = {1992},
	note = {ISI Document Delivery No.: JX295Times Cited: 14Cited Reference Count: 80},
	month = {Nov},
	pages = {6309-6321},
	type = {Article},
	abstract = {The reaction rates of the muonium (Mu) atom with HBr and HI in approximately 1 atm N2 moderator have been measured over the temperature range 160-490 K using the muSR technique. While both abstraction and exchange reactions are possible, only the abstraction reaction should be observable, being moderately exothermic. Comparisons with the corresponding H(D) reactions reveal small kinetic isotope effects in both reactions, which do not vary strongly with temperature (k(Mu)/k(H) almost-equal-to 3.5 near 300 K), consistent with the (classical) ratio of mean velocities. Surprisingly, quantum tunneling, normally facile for similarly exothermic reactions of the ultralight Mu atom (m(Mu)/M(H) almost-equal-to 1/9), appears to be of little importance here. This despite the fact that the (temperature-independent) experimental activation energies are much less than the expected vibrationally adiabatic barrier heights (estimated to be almost-equal-to 1. 5 kcal mol-1) and, particularly in the case of Mu + HI, much less than the corresponding H-atom activation energy: 0. 13 +/- 0.03 vs 0.70 +/- 0. 3 kcal mol-1. In the case of reactions with HBr, the experimental Mu- and H-atom activation energies are much more similar: 0. 51 +/- 0.03 and 0.74 +/- 0. 12 kcal mol-1, respectively, over comparable temperature ranges. These data pose a conundrum in which several compensating effects related to the much lighter Mu-atom mass seem to be involved. Theoretical calculations are urgently required. In our view the topography of the potential-energy surface(s) for H-2X is poorly known, particularly in the region of the barrier. It may be that the abstraction barriers for both Mu + HI and Mu + HBr are considerably later and even smaller than current calculations indicate, resulting in a cancellation of the effects of zero-point-energy shifts and quantum tunneling at the transition state. Differences in skewing angles between Mu and H + HX could favor a shorter tunneling path for the H-atom reaction, possibly compensating for its heavier mass. Steric or rebound effects from "bottlenecks" on the (mass-weighted) potential surfaces for Mu reactivity may also play some role. An upper limit for the 300 K reaction rate of Mu + HCI is given as well. In contrast to both HBr and HI, this reaction is quite endothermic and hence exhibits an inverse kinetic isotope effect (k(Mu) much less than k(H)).},
	keywords = {ABSTRACTION REACTIONS, CALCULATIONS, CHEMICAL-REACTIONS, EV COLLISION ENERGY, EXCHANGE-REACTIONS, H+HX COLLISIONS, ISOTOPIC, POTENTIAL-ENERGY SURFACE, QUANTUM-MECHANICAL, RATE CONSTANTS, TRANSITION-STATE THEORY, VARIANTS},
	isbn = {0021-9606},
	url = {<Go to ISI>://A1992JX29500038},
	author = {Gonzalez, A. C. and Tempelmann, A. and Arseneau, D. J. and Fleming, Donald G. and Senba, M. and Kempton, J. R. and Pan, J. J.}
}
