Ortho-Positronium in Some n-Alkanes; Influence of Temperature and Pressure

Abstract

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.