Positron and orthopositronium decay rates in helium at high densities

Journal Article · Tue Mar 01 04:00:00 EST 1977 · Phys. Rev., A; (United States)

DOI:https://doi.org/10.1103/PhysRevA.15.1340· OSTI ID:7124425

Fox, R A; Canter, K F; Fishbein, M

Positron and orthopositronium (o-Ps) decay rates have been obtained in helium gas over the density ranges 72--200 and 80--520 amagat at gas temperatures 300 and 77 degreeK, respectively. The 77 degreeK o-Ps results exhibit the onset of bubblelike behavior observed by other investigators. The 300 degreeK o-Ps decay rates are in agreement with a linear extrapolation of the high-precision low-density results obtained by Coleman et al. and are in marked disagreement with the density-dependent pickoff annihilation coefficient proposed by Ferrell. The free-positron decay rates are the first to be obtained above 200 amagat at well above saturated vapor temperatures. Above 200 amagat, the free-positron Z/sub eff/ is found to exhibit an unambiguous decrease with increasing density. At 520 amagat, for example, Z/sub eff/ = 3.71 +- 0.02, as opposed to the density-independent value, Z/sub eff/ = 3.89 +- 0.04 observed in the low-density regime.

• Research Organization: Department of Physics, Brandeis University, Waltham, Massachusetts 02154
• OSTI ID: 7124425
• Journal Information: Phys. Rev., A; (United States), Journal Name: Phys. Rev., A; (United States) Vol. 15:3; ISSN PLRAA
• 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
ANNIHILATION
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
ATOM COLLISIONS
BASIC INTERACTIONS
COLLISIONS
CRYOGENIC FLUIDS
DECAY
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
FLUIDS
HELIUM
HIGH PRESSURE
INTERACTIONS
LEPTONS
NONMETALS
POSITRON COLLISIONS
POSITRON-ATOM COLLISIONS
POSITRONIUM
POSITRONS
RARE GASES
SCATTERING LENGTHS