Direct evidence of positronium trapping in the cavity of crown ether

We report a new result on positron age–momentum correlation measurement in crown ethers. While the ortho-positronium lifetime shows good correlation with the cavity size of crown ethers, the intensity is seen to be dependent on the chemical structure. It is seen that a linear correlation of the momentum distribution of free-positron and o-Ps extracted from the AMOC spectra with the energy of the HOMO level evaluated using PM3 method. This correlation unambiguously suggests that positrons have a strong affinity for the ether ring and it provides direct experimental evidence for localization of positronium atom in the crown ether cavity.