Ortho-Positronium in Some n-Alkanes; Influence of Temperature and Pressure
B. Zgardzińska, M. Pietrow, T. Goworek and J. Wawryszczuk
Department of Nuclear Methods, Institute of Physics, Maria Curie-Skłodowska University, pl. Marii Curie Skłodowskiej 1, 20-031 Lublin, Poland
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Received: 5 06 2006;
Positron lifetime spectra were measured for a series of odd-numbered n-alkanes from C11H24 to C19H40 as a function of temperature and pressure. The ortho-Ps lifetimes in the rotator phase and the increase in intensity at the transition to that phase can be explained by location of Ps in the vicinity of kink-type conformers. The relation between o-Ps lifetime and molecule length can be described in the framework of extended Tao-Eldrup model. One can eliminate the effect of intensity rise in time by sample illumination or by application of high pressure. A decrease in temperature by 1 K is equivalent to an increase in pressure by about 4 MPa.
DOI: 10.12693/APhysPolA.110.747
PACS numbers: 36.10.Dr, 61.80.Fe, 71.60.+z, 78.70.Bj