title: Optical spectroscopy of molecular positronium.
abstract: We report optical spectroscopic measurements of molecular positronium (Ps(2)), performed via a previously unobserved L=1 excited state. Ps(2) molecules created in a porous silica film, and also in vacuum from an Al(111) crystal, were resonantly excited and then photoionized by pulsed lasers, providing conclusive evidence for the production of this molecular matter-antimatter system and its excited state. Future experiments making use of the photoionized vacuum L=1 Ps(2) could provide a source of Ps(+) ions, as well as other multipositronic systems, such as Ps(2)H(-) or Ps(2)O.
authors.affiliation: Department of Physics and Astronomy, University of California, Riverside, California 92521-0413, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Cassidy
authors.forename: T H
authors.initials: TH
authors.lastname: Hisakado
authors.forename: H W K
authors.initials: HW
authors.lastname: Tom
authors.forename: A P
authors.initials: AP
authors.lastname: Mills