Hot muonium and muon spur processes in nitrogen and ethane

Journal Article · Tue Jan 15 04:00:00 EST 1991 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.460061· OSTI ID:6045908

Kempton, J R; Senba, M; Arseneau, D J; Gonzalez, A C; Garner, D M; Pan, J J ^[1]; Fleming, D G ^[2]; Percival, P W; Brodovitch, J; Leung, S ^[3]

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1. TRIUMF and Department of Chemistry, University of British Columbia, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3 (CA)
2. Department of Chemistry and TRIUMF, University of British Columbia, 2036 Main Mall, Vancouver, B.C. V6T 1Y6, (Canada) Meson Science Institute, University of Tokyo, Hongo-113, Tokyo, (Japan)
3. TRIUMF and Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, (Canada)

Muon polarizations are reported for nitrogen and ethane over a wide pressure range from below 1 to 200 atm for N{sub 2} and up to 245 atm for C{sub 2}H{sub 6}. The N{sub 2} measurements were made at ambient temperature, while those for C{sub 2}H{sub 6} 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 N{sub 2} and about 10 atm for C{sub 2}H{sub 6}, the muonium polarization increases with pressure. This is well understood in terms of epithermal charge exchange. In N{sub 2} there is a small diamagnetic fraction, which is ascribed to the N{sub 2}Mu{sup +} 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 C{sub 2}H{sub 6}, 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, C{sub 2}H{sub 6}Mu{sup +}+C{sub 2}H{sub 6}{r arrow}C{sub 2}H{sub 5}Mu+C{sub 2}H{sup +}{sub 7}, trapping the muon in a diamagnetic product. Both N{sub 2} and C{sub 2}H{sub 6} 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 N{sub 2}, the missing fraction is recovered at pressures beyond about 150 atm, which is explained by scavenging of electrons by positive ions.

• OSTI ID: 6045908
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 94:2; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400701 -- Radiochemistry & Nuclear Chemistry-- Hot-Atom Chemistry
640303* -- Atomic
Molecular & Chemical Physics-- Positronium
Muonium
& Muonic & Mesic Atoms & Molecules
74 ATOMIC AND MOLECULAR PHYSICS
ADDUCTS
ALKANES
AMBIENT TEMPERATURE
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
CHARGE EXCHANGE
CHARGED PARTICLES
CHEMISTRY
ELEMENTARY PARTICLES
ELEMENTS
ETHANE
FERMIONS
HIGH PRESSURE
HOT ATOM CHEMISTRY
HYDROCARBONS
IONS
LEPTONS
MEDIUM PRESSURE
MEDIUM TEMPERATURE
MESIC MOLECULES
MOLECULAR IONS
MOLECULES
MUON SPIN RELAXATION
MUONIC MOLECULES
MUONIUM
MUONS
MUONS PLUS
NITROGEN
NONMETALS
ORGANIC COMPOUNDS
POLARIZATION
RADIOCHEMISTRY
RELAXATION
SLOWING-DOWN
SPIN EXCHANGE
THERMALIZATION