title: Experimental evidence for spin-orbit interactions in positronium-Xe collisions.
abstract: Spin-orbit interaction of positronium (Ps) with the surrounding atoms, predicted by Mitroy and Novikov [Phys. Rev. Lett. 90, 183202 (2003)], has been detected experimentally. We have found that the lifetime of the magnetically unperturbed ortho-Ps in Xe gas of 1 atm decreases significantly when a magnetic field of 1.0 T is applied. This decrease is attributed to the Ps spin conversion caused by spin-orbit interaction during Ps-Xe collision. The annihilation cross section of ortho-Ps due to this interaction has been determined to be 3 times as large as that expected by Mitroy and Novikov.
authors.affiliation: Institute of Physics, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1, Komaba, Tokyo, 153-8902, Japan. saitou@youshi.c.u-tokyo.ac.jp
authors.forename: Haruo
authors.initials: H
authors.lastname: Saito
authors.forename: Toshio
authors.initials: T
authors.lastname: Hyodo