@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.}
}
