The temperature dependence of the positronium bubble state. An angular correlation and doppler broadening study of a phenyl ether

Abstract

Abstract Positron annihilation angular correlation and Doppler broadening measuremennts are reported as a function of temperature for the supercooling liquid bis[m-(m-phenoxyphenoxy)phenyl]ether (6PO). A comparison of these observations with predictions based on lifetime measurements is presented and indicates limitations of particular experiments in characterising the annihilation processes. The ratio I′3/I1, where I′3 is the ortho-Ps yield and I1 the narrow-peak intensity, was observed to be 4–6 instead of its “ideal” value of 3 in the glassy state. This is interpreted as evidence for a Ps center-of-mass wavefunction consisting of a component strongly localized on the Ps trap and a broader, “spilled over” component. Only the latter gives rise to a narrow peak of intensity I1. The variation of I′3/I1 with temperature depends on the Ps state and hence, provides evidence for the effect of the initial size of the Ps trap and the molecular motion within the Ps lifetime.