Observation of Positronium Specular Reflection from LiF

M. H. Weber; S. Tang; S. Berko; B. L. Brown; K. F. Canter; K. G. Lynn; A. P. Mills, Jr; L. O. Roellig; A. J. Viescas

doi:10.1103/PhysRevLett.61.2542

Observation of Positronium Specular Reflection from LiF

M. H. Weber, S. Tang, S. Berko, B. L. Brown, K. F. Canter, K. G. Lynn, A. P. Mills, Jr., L. O. Roellig, and A. J. Viescas

Phys. Rev. Lett. 61, 2542 – Published 28 November 1988

Abstract

A monoenergetic positronium (Ps) beam of 0-60-eV energy and an angular width of ±5° is created by charge-exchange collisions of a slow positron beam passing through an Ar gas cell. The Ps beam is directed at a Lif(100) crystal, and reflected Ps atoms are detected at an annihilation target. With angles of incidence of 50° to 60° we observe a specularly reflected beam with a maximum reflected fraction $R = (30 \pm 5) %$ at a Ps energy of 7 eV. At higher energies (20-60 eV) the reflectivity ( $R = 0.5 %$ at 60 eV) can be ascribed principally to a short Ps mean free path $λ = (0.75 \pm 0.15)$ Å, and to a lesser extent a Ps inner potential of about 4 eV.

Received 26 July 1988

DOI:https://doi.org/10.1103/PhysRevLett.61.2542

Authors & Affiliations

M. H. Weber¹, S. Tang¹, S. Berko², B. L. Brown^3,*, K. F. Canter², K. G. Lynn⁴, A. P. Mills, Jr.³, L. O. Roellig¹, and A. J. Viescas^1,†

¹City University of New York, New York, New York 10036
²Brandeis University, Waltham, Massachusetts 02154
³AT&T Bell Laboratories, Murray Hill, New Jersey 07974
⁴Brookhaven National Laboratory, Upton, New York 11973

^*Present address: Department of Physics, Harvard University, Cambridge, MA 02138.
^†Present address: Department of Physics, Brookhaven National Laboratory, Upton, NY 11973.