Positronium hydride in hydrogen-laden thermochemically reduced MgO single crystals

Journal Article · Sun Apr 01 04:00:00 EDT 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.41.6220· OSTI ID:7002942

Pareja, R; Pedrosa, M A; Gonzalez, R ^[1]; Chen, Y ^[2]

---

1. Departamento de Fisica de Materiales, Facultad de Ciencias Fisicas, Universidad Complutense, 28040 Madrid, Spain (ES)
2. Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (USA)

Thermochemical reduction of hydrogen-laden MgO single crystals at {ital T}{approx}2400 K results in a large concentration of both hydride (H{sup {minus}}) ions and anion vacancies ({gt}10{sup 24} m{sup {minus}3}). Positron-lifetime experiments of these crystals provide evidence for bound positronium hydride states also referred to as ({ital e}{sup +}-H{sup {minus}}) or PsH states. The presence of the anion vacancies was found to inhibit the formation of these states. After thermally annealing out these vacancies, such that H{sup {minus}} concentration remains intact, two long-lived components appear in the lifetime spectrum. Furthermore, these two components correlate with the presence of the H{sup {minus}}ions. These results suggest the existence of bound ({ital e}{sup +}-H{sup {minus}}) states when positrons are trapped by the H{sup {minus}} ions, and the subsequent formation of positronium (Ps) states by the dissociation of the ({ital e}{sup +}-H{sup {minus}}) states. From the values of the intermediate lifetime component, a value of (570{plus minus}50) ps is obtained for the lifetime of the PsH state located in an anion vacancy in MgO. The longest lifetime component {approx}(1--3) ns is attributed to pick-off annihilation of ortho-Ps states.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 7002942
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 41:10; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

640303* -- Atomic
Molecular & Chemical Physics-- Positronium
Muonium
& Muonic & Mesic Atoms & Molecules
74 ATOMIC AND MOLECULAR PHYSICS
ALKALINE EARTH METAL COMPOUNDS
ANIONS
BOUND STATE
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTIONS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTALS
HYDRIDES
HYDROGEN COMPOUNDS
IONS
LIFETIME
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MONOCRYSTALS
OXIDES
OXYGEN COMPOUNDS
POINT DEFECTS
POSITRONIUM COMPOUNDS
REDUCTION
SYNTHESIS
THERMOCHEMICAL PROCESSES
VACANCIES
VERY HIGH TEMPERATURE