Oxygen quenching of positronium in silica gels
Positronium decay rates have been measured in silica gels of various pore sizes, at two temperatures, 297 and 77 K, and as a function of oxygen concentration. The cross section of positronium quenching due to a monolayer of adsorbed O2 at 77 K is found to be at least two orders of magnitude smaller than the cross section for conversion quenching by subsequent layers, and is similar to that observed in gaseous oxygen. No evidence of chemical quenching has been observed. The positronium atom occurs in two ground states. Parapositronium (p -Ps) is the singlet state with total spin of zero and it has a self annihilation lifetime in vacuum of 0.125 ns, and decays via 2 gamma emission. Orthopositronium (o-Ps) is the triplet state with total spin of one. Its free space lifetime is much longer, 140 ns, and decays via 3 gamma emission.
- Research Organization:
- Texas Christian Univ., Fort Worth, TX (USA). Dept. of Physics
- OSTI ID:
- 5986558
- Report Number(s):
- AD-A-226917/3/XAB; CNN: AFOSR-90-0165
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201 -- Chemical & Physicochemical Properties
656002* -- Condensed Matter Physics-- General Techniques in Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
ADSORBENTS
ANNIHILATION
BASIC INTERACTIONS
CHALCOGENIDES
CROSS SECTIONS
DECAY
ELECTROMAGNETIC INTERACTIONS
ELEMENTS
ENERGY LEVELS
FLUIDS
GASES
GROUND STATES
INTERACTIONS
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
POROSITY
POSITRONIUM
QUANTITY RATIO
QUENCHING
SILICA GEL
SILICON COMPOUNDS
SILICON OXIDES
SORPTIVE PROPERTIES
SURFACE PROPERTIES