The electronic structure and positron annihilation characteristics of positronium halides (X/sup -/; e/sup +/). II. Two-photon annihilation

Journal Article · Tue Mar 15 00:00:00 EST 1977 · J. Chem. Phys.; (United States)

OSTI ID:7106554

Farazdel, A; Cade, P E

The basic characteristics of two-photon positron annihilation from the ground and first-excited states of (F/sup -/;e/sup +/), (Cl/sup -/;e/sup +/), (Br/sup -/;e/sup +/), and (I/sup -/;e/sup +/) are calculated. The properties of interest are the annihilation rate GAMMA, the orbital components to the annihilation rate GAMMA/sub nl/, and the angular correlation N(theta) for two photon annihilation. The two states considered are the ...ns/sup 2/np/sup 6/1s/sub +/, /sup 2/S and the ...ns/sup 2/np/sup 6/2p/sub +/, /sup 2/P states of (X/sup -/;e/sup +/), and all computations presented are based on the restricted Hartree--Fock wave functions for the (X/sup -/;e/sup +/) states published elsewhere. These results are compared with experiment from various sources and an assessment of the potential role of the (X/sup -/;e/sup +/) /sup 2/S and /sup 2/P states is attempted. These results serve to limit the speculation on the role of (X/sup -/;e/sup +/) bound-state positron systems in the two-gamma annihilation from alkali halide crystals. The calculated lifetimes for the /sup 2/S states are 1.7, 4.0, 5.0, and 6.8 nsec for (F/sup -/;e/sup +/), (Cl/sup -/;e/sup +/), (Br/sup -/;e/sup +/), and (I/sup -/;e/sup +/), respectively. These RHF results obviously place too little electron density at the position of the positron and hence give lifetimes which are at best an upper limit to the true lifetimes (these lifetimes are too high by a factor of about ten). The angular correlation data for the (Cl/sup -/;e/sup +/) system provides an apparently striking confirmation of the recent experimental identification of a stable chloride/positron system by study of the angular correlation from aqueous solutions by Mogensen and Shantarovich.

• Research Organization: Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003
• OSTI ID: 7106554
• Journal Information: J. Chem. Phys.; (United States), Vol. 66:6
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
BROMINE
POSITRONIUM COMPOUNDS
CHLORINE
FLUORINE
IODINE
ANNIHILATION
ELECTRONIC STRUCTURE
ANGULAR CORRELATION
BROMINE IONS
CHLORINE IONS
FLUORINE IONS
HALIDES
IODINE IONS
LIFETIME
LIMITING VALUES
POSITRON-ION COLLISIONS
POSITRONIUM
POSITRONIUM CHEMISTRY
S STATES
BASIC INTERACTIONS
CHARGED PARTICLES
COLLISIONS
CORRELATIONS
ELECTROMAGNETIC INTERACTIONS
ELEMENTS
ENERGY LEVELS
HALOGEN COMPOUNDS
HALOGENS
INTERACTIONS
ION COLLISIONS
IONS
NONMETALS
POSITRON COLLISIONS
640303* - Atomic
Molecular & Chemical Physics- Positronium
Muonium
& Muonic & Mesic Atoms & Molecules