@article {1551,
	title = {Slowing-down times and stopping powers for similar to 2-MeV mu(+) in low-pressure gases},
	journal = {Physical Review A},
	volume = {74},
	number = {4},
	year = {2006},
	note = {ISI Document Delivery No.: 101EXTimes Cited: 3Cited Reference Count: 86Senba, Masayoshi Arseneau, Donald J. Pan, James J. Fleming, Donald G.},
	month = {Oct},
	pages = {17},
	type = {Article},
	abstract = {The times taken by positive muons (mu(+)) to slow down from initial energies in the range similar to 3 to 1 MeV, to the energy of the last muonium formation, approximate to 10 eV, at the end of cyclic charge exchange, have been measured in the pure gases H-2, N-2, Ar, and in the gas mixtures Ar-He, Ar-Ne, Ar-CF4, H-2-He, and H-2-SF6, by the muon spin rotation (mu SR) technique. At 1 atm pressure, these slowing-down times, tau(SD), in Ar and N-2, vary from similar to 14 ns at the highest initial energies of 2.8 MeV to 6.5 ns at 1.6 MeV, with much longer times, similar to 34 ns, seen at this energy in H-2. Similar variations are seen in the gas mixtures, depending also on the total charge and nature of the mixture and consistent with well-established (Bragg) additivity rules. The times tau(SD) could also be used to determine the stopping powers, dE/dx, of the positive muon in N-2, Ar, and H-2, at kinetic energies near 2 MeV. The results demonstrate that the mu(+) and proton have the same stopping power at the same projectile velocity, as expected from the historic Bethe-Bloch formula, but not previously shown experimentally to our knowledge for the muon in gases at these energies. The energy of the first neutralization collision forming muonium (hydrogen), which initiates a series of charge-exchanging collisions, is also calculated for He, Ne, and Ar. The formalism necessary to describe the stopping power and moderation times, for either muon or proton, in three energy regimes-the Bethe-Bloch, cyclic charge exchange, and thermalization regimes-is developed and discussed in comparison with the experimental measurements reported here, and elsewhere. The slowing-down times through the first two regimes are controlled by the relevant ionization and charge-exchange cross sections, whereas the final thermalization regime is most sensitive to the forwardness of the elastic scattering cross sections. In this regime the slowing-down times (to kT) at nominal pressures are expected to be less than or similar to 100 ns.},
	keywords = {ALPHA-PARTICLES, BINARY THEORY, CHARGE-EXCHANGE, COMPETING PROCESSES, CROSS-SECTIONS, ELECTRON-SPIN EXCHANGE, HYDROGEN-ATOMS, MUONIUM-FORMATION, POSITIVE MUONS, RADIATION-CHEMISTRY},
	isbn = {1050-2947},
	url = {<Go to ISI>://000241723100090},
	author = {Senba, M. and Arseneau, D. J. and Pan, J. J. and Fleming, Donald G.}
}
@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 {2960,
	title = {FIRST SPECTROSCOPIC EVIDENCE FOR A MUONIUM-CONTAINING MOLECULE - NEMU-ASTERISK CHEMILUMINESCENCE},
	journal = {Journal of Chemical Physics},
	volume = {101},
	number = {2},
	year = {1994},
	note = {ISI Document Delivery No.: NW979Times Cited: 4Cited Reference Count: 102},
	month = {Jul},
	pages = {1202-1218},
	type = {Review},
	abstract = {Evidence for the formation of NeMu*, an isotopic analog of the Rydberg molecule NeH*, has been obtained from the observation of chemiluminescent emission in the near-infrared region. This is the first spectroscopic detection of a muonium-containing molecule. NeMu* was formed by stopping a 4 MeV muon (mu(+)) beam in a target vessel containing 1-6 atm of Ne and. similar to 1 Torr Ar. The wavelength spectrum of the emission, from similar to 680-1000 nm, was measured, using a variable-wavelength filter, with a resolution of +/-12.5 nm. Lower resolution spectra were also taken with a series of long pass filters. A complete histogram of photon events vs time was collected for each wavelength. Two strong transitions are observed, centered at 818 and 943 nm. Identification of NeMu* was made by a comparison of the experimental spectrum with a simulated spectrum based on detailed ad initio calculations, extended to higher excitation levels than had heretofore been reported. Both experimental and theoretical results are reported here. Although the mechanism by which the emitting states in NeMu* are formed remains unclear, radiolysis effects appear to play a dominant role, indicating that NeMu(+) (the product of muon thermalization in Ne) undergoes charge exchange with metastable Ar* and/or is neutralized by a spur electron, both species produced during the slowing down of the high energy muon.},
	keywords = {2-SIGMA-2-SIGMA TRANSITIONS, CHARGE-EXCHANGE COLLISIONS, COMPETING PROCESSES, DISSOCIATION, EMISSION-SPECTRA, EXCITED-STATES, GAUSSIAN-BASIS SETS, radiative, RARE-GAS HYDRIDES, REACTION-KINETICS, Rydberg states},
	isbn = {0021-9606},
	url = {<Go to ISI>://A1994NW97900034},
	author = {Baer, S. and Fleming, Donald G. and Sloan, J. J. and Arseneau, D. J. and Kolbuszewski, M. and Wright, J. and Senba, M. and Pan, J. J. and Snooks, R.}
}
@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 = {<Go to ISI>://A1991EY07000050},
	author = {Duchovic, R. J. and Wagner, A. F. and Turner, R. E. and Garner, D. M. and Fleming, Donald G.}
}
@article {7042,
	title = {HOT MUONIUM AND MUON SPUR PROCESSES IN NITROGEN AND ETHANE},
	journal = {Journal of Chemical Physics},
	volume = {94},
	number = {2},
	year = {1991},
	note = {ISI Document Delivery No.: EU592Times Cited: 15Cited Reference Count: 100},
	month = {Jan},
	pages = {1046-1059},
	type = {Article},
	abstract = {Muon polarizations are reported for nitrogen and ethane over a wide pressure range from below 1 to 200 atm for N2 and up to 245 atm for C2H6. The N2 measurements were made at ambient temperature, while those for C2H6 were made at temperatures both above and below the critical temperature (305.3 K). This is the first mu-SR study of muonium and diamagnetic muon formation to cover the entire range from a low pressure gas to densities typical of liquids. The data are discussed in terms of hot atom and spur models. In the lowest pressure range, below 1.5 atm for N2 and about 10 atm for C2H6, the muonium polarization increases with pressure. This is well understood in terms of epithermal charge exchange. In N2 there is a small diamagnetic fraction, which is ascribed to the N2Mu+ molecular ion. This fraction approaches zero as the pressure is increased to 200 atm, with a corresponding increase in the muonium fraction, consistent with charge neutralization of the molecular ion by electrons from the radiolysis track. In C2H6, there is a decrease in the muonium fraction and a concomitant increase of the diamagnetic fraction with density, the changes occurring in two stages. The initial change is explained by stabilization of the vibrationally excited substitution products of hot muonium reactions. The second one is explained by proton transfer from the molecular ion adduct, C2H6Mu+ + C2H6 {\textendash}> C2H5Mu + C2H7+, trapping the muon in a diamagnetic product. Both N2 and C2H6 have a missing fraction of polarization above 10 atm, most likely due to spin exchange of Mu with paramagnetic species created in the muon track. In N2, the missing fraction is recovered at pressures beyond about 150 atm, which is explained by scavenging of electrons by positive ions. In C2H6 the missing fraction is roughly constant for densities beyond 5 mol l-1 (almost-equal-to 50 atm), and about twice the maximum found for N2. Both facts are consistent with the existence of ethyl radicals and hydrogen atoms in C2H6, which are longer lived than the spur electrons.},
	keywords = {ATOM CHEMISTRY, CHARGE-EXCHANGE, COLLISIONS, COMPETING PROCESSES, DEPOLARIZATION, HYDRATED ELECTRONS, LIQUIDS, MOLECULAR-HYDROGEN, NONPOLAR, QUANTIZED RRK THEORY, RECOIL TRITIUM REACTIONS, SPIN, UNIMOLECULAR REACTION-RATES},
	isbn = {0021-9606},
	url = {<Go to ISI>://A1991EU59200025},
	author = {Kempton, J. R. and Senba, M. and Arseneau, D. J. and Gonzalez, A. C. and Garner, D. M. and Pan, J. J. and Fleming, Donald G. and Percival, P. W. and Brodovitch, J. C. and Leung, S. K.}
}
@article {6827,
	title = {MUONIUM FORMATION IN XENON AND ARGON UP TO 60 ATMOSPHERES},
	journal = {Hyperfine Interactions},
	volume = {65},
	number = {1-4},
	year = {1990},
	note = {ISI Document Delivery No.: EZ856Times Cited: 15Cited Reference Count: 265TH INTERNATIONAL CONF ON MUON SPIN ROTATION RELAXATION AND RESONANCEAPR 09-12, 1990OXFORD, ENGLAND},
	pages = {801-809},
	type = {Proceedings Paper},
	abstract = {Results of muon polarization studies in xenon and argon up to 60 atm are reported. In argon for pressures up to 10 atm, the muon polarization is best explained by an epithermal-charge exchange model. Above this pressure, the decrease in P(D) and increase in P(L) are ascribed to charge neutralization and spin exchange reactions, respectively, in the radiolysis track. Measurements with Xe/He mixtures with a xenon pressure of 1 atm indicate that the lost polarization in the pure xenon at this pressure is due to inefficient moderation of the muon. As the pressure in pure xenon is increased above 10 atm, we find that P(L) remains roughly constant and P(D) begins to increase. The lost fraction may be due to the formation of a XeMu Van der Waals type complex, while P(D) is ascribed to XeMu+ formation. This suggests that spur processes appear to be less important in xenon than in argon.},
	keywords = {CHARGE-EXCHANGE COLLISIONS, COMPETING PROCESSES, DEPOLARIZATION, GASES, HOT ATOM CHEMISTRY, HYDRATED ELECTRONS, LIQUIDS, POSITRONIUM, SPIN EXCHANGE, XE},
	isbn = {0304-3843},
	url = {<Go to ISI>://A1990EZ85600008},
	author = {Kempton, J. R. and Senba, M. and Arseneau, D. J. and Gonzalez, A. C. and Pan, J. J. and Tempelmann, A. and Garner, D. M. and Fleming, Donald G.}
}
@article {6897,
	title = {POSITIVE MUON SLOWING DOWN TIMES IN AR MEASURED BY THE MU-SR TECHNIQUE},
	journal = {Hyperfine Interactions},
	volume = {65},
	number = {1-4},
	year = {1990},
	note = {ISI Document Delivery No.: EZ856Times Cited: 13Cited Reference Count: 125TH INTERNATIONAL CONF ON MUON SPIN ROTATION RELAXATION AND RESONANCEAPR 09-12, 1990OXFORD, ENGLAND},
	pages = {793-799},
	type = {Proceedings Paper},
	abstract = {The phase information of triplet muonium signals has been used to measure the slowing down times of the positive muon in Ar. The results agree well with calculated stopping power based on proton data with the assumption that the positive muon and proton have the same stopping power at the same projectilew velocity (velocity scaling).},
	keywords = {CHARGE-EXCHANGE COLLISIONS, COMPETING PROCESSES, GASES},
	isbn = {0304-3843},
	url = {<Go to ISI>://A1990EZ85600007},
	author = {Senba, M. and Arseneau, D. J. and Gonzalez, A. C. and Kempton, J. R. and Pan, J. J. and Tempelmann, A. and Fleming, Donald G.}
}
