CSE Colloquium Series
ARGONNE NATIONAL LABORATORY
CHEMICAL SCIENCES AND ENGINEERING DIVISION
SPEAKER: David Schrader
Marquette University
TITLE: New Chemistry: Compounds that Contain Positrons
TIME: 11:00 am
(Refreshments will be available starting at 10:45 am in front lobby)
DATE: February 18, 2008
PLACE: Building 200, Auditorium
HOST: Chuck Jonah
Abstract: A few dozen positron-containing compounds have been shown to be stable against dissociation. These include: PsCl, positronium chloride; e+Li, positronic lithium; Ps2O, dipositronium oxide; Ps2, dipositronium; PsH, positronium hydride; e+CnH2n+2 for 2 <= n <= 14, ethyl positride or positroethane, etc. All but the last three are known from quantum calculations only. Annihilation lifetimes are ~500 ps, half that for the species containing two positrons. This is several orders of magnitude longer than typical vibrational periods.
I will describe the single direct experimental determination of a binding energy, that of PsH, which was performed by me and collaborators in Denmark in 1991.[1] A modern version of that experiment using the new positron beam at the CSE Radiation Chemistry Group is proposed and will be discussed.
Diatomic positronium, Ps2, was recently prepared by Cassidy and Mills.[2] We will discuss prospects for preparing the 2-positron compounds CPs2 and Ps2O[3] with the ANL/CSE beam.
1D. M. Schrader, F. M. Jacobsen, N.-P. Frandsen, and U. Mikkelsen, Phys. Rev. Lett. 69, 57 (1992)
2D. B. Cassidy and A. P. Mills, Jr., Nature 449, 195 (2007)
3N. Jiang and D. M. Schrader, Phys. Rev. Lett. 81, 5113 (1998). [Erratum, ibid. 82, 4735 (1999)]