Formation of positronium hydride

Abstract

We report the formation of positronium hydride (PsH) in collisions between positrons and methane. A preliminary value of 1.1 ±0.2 eV for the binding energy of PsH is obtained. PACS numbers: 36.IO.-k, 35.20.Gs Since the existence of the positronium atom (Ps) was predicted [1] and later experimentally discovered [2], there has been much theoretical and experimental interest in studying the possibilities of forming Ps-containing molecules. The simplest of these are the polyleptons Ps 2 and Ps". Beside these, PsH, PsF, PsCl, PsBr, and PsI have all been predicted to be chemically stable from quantal calculations [3-6]. Many other, more complicated, Ps-containing molecules are thought to be stable [7]. _ Ps has been observed by Mills [8] whereas none of the other simple molecules have been observed in vacuum. However, several of the halogen compounds have been produced and identified in aqueous solutions [9] and in graphite [10]. Much less convincing experimental results suggest the formation of PsH in various kinds of condensed matter [11,12]. Below, we report an experiment in which PsH is formed in positron collisions with CH 4 . The stability of the PsH molecule was first established by Ore [5] who found it to be bound by at least 0.0683 eV. Later, many other theoretical studies of PsH have confirmed its stability with the most accurate calculation by Ho [13] yielding a binding energy, #p S H, of 1.0598 eV.

Ground-state energy and relativistic corrections for positronium hydride

“…In 1992, Schrader et al reported [20] the formation of positronium hydride in collisions between positrons and methane and gave an estimate of the binding energy, 1.1±0.2 eV. Recently, positronium physics and chemistry gained new impetus when the first experimental observation of the positronium molecule was reported [21,22].…”

Hyperfine structure and -pair annihilation in the muonium–positronium MuPs and positronium hydrides

“…Almost 20 years ago the 1 HPs hydride was created in the laboratory during collisions between positrons and methane [4]. Theoretically, the positronium hydride ∞ HPs has extensively been investigated in earlier studies [5] - [10], [11], [12] (all references on HPs before 1998 can be found in [13]).…”

Internal energy deposition into molecules upon positron-electron annihilation

“…Schrader and co-workers [4] studied the formation of positronium compounds. Recently the authors [5] have reported some unexpected results showing that positrons having energies below the Ps thresholds induce extensive fragmentation of decane, tetraethylsilane, and butylbenzene.…”