Positronium in binary mixture n-nonadecane+n-tricosane at high pressure

Positron annihilation lifetime spectra (PALS) in binary mixture of alkanes were measured as a function of pressure. It was found that after rapid transition from rotator to rigid phase the intensity of positronium formation is not stable in time; its relaxation contains two components differing by an order of magnitude. The appearance of transient rotator phase, analogous to that observed in temperature dependences for the same mixture was not observed. Two-stage increase of spectrum parameters at crossing the rigid–rotator transition by pressure reduction can be an indication of the appearance of an additional phase preceding the rotator.