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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 3 (1974), S. 1-7 
    ISSN: 1432-0630
    Keywords: Positronium ; Molecular substances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The progress of research into the behavior of the positronium in molecular substances in the last several years is reviewed. The Ps atom can be treated as a solute in a liquid. The repulsive exchange force is the dominant force which reacts against the van der Waals attractive force. One of the most useful general relationships found is the one between the pick-off quenching rate and the surface tension of the liquid. The pick-off quenching rate is found, in general, to be an additive property of the functional groups of a molecule. The quenching of theo-Ps atom by an active quenching agent in an inert solvent has been found to be primarily diffusion controlled. Some deviations from the simple Arrhenius equation have been found. For gases, more theoretical work on the collision problems of Ps with atoms or molecules is needed. For amorphous molecular solids, it is likely that the property of pick-off quenching ofo-Ps is similar to that in liquids. However, in crystalline molecular solids, the situation is quite different. A few definite cases have been found where a Ps atom does not form or exist. Further work in this area should be very interesting. The foregoing leads us to believe that positronium or positron annihilation can be useful in the study of fundamental properties of molecular liquids and solids.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0630
    Keywords: Positronium ; Diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The temperature effect on positronium quenching rates for p-benzoquinone and iodine in several solvents was determined. The quenching rate constantk 1 follows ak 1∝1/η relationship better than thek 1∝T/η one, predicted by ordinary theory. A simple theoretical treatment based on diffusion theory shows that the temperatureT of the solute, positronium, may not be the same as the temperature of the solvent if the positronium is not fully thermalized. This temperature is found to be about twice the room temperature for the solvents investigated. The findings further support the theory that positronium reactions are “diffusion controlled” in liquid solutions. The activation energies of all the positronium reactions studied are either negligible or less than 0.1 eV.
    Type of Medium: Electronic Resource
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