Beyond the Point Ps Approximation
In application to positron annihilation spectroscopy, Ps atom is considered not as a point particle, but as a finite size e+e- pair localized in a bubble-like state in a medium. It is shown that during transition from quasifree to localized state, variation of the internal Coulombic e+-e- attraction energy (several eV) plays an important role, which may govern Ps localization process.
Jozef Krištiak, Jan Kuriplach and Pradeep K. Pujari
S. V. Stepanov et al., "Beyond the Point Ps Approximation", Materials Science Forum, Vol. 733, pp. 7-14, 2013