Annihilation of positrons in gaseous and liquid NH3 and in NH3–Ar and NH3–Ne mixtures

Publisher Website
Google Scholar
Abstract
The lifetime spectra of positrons annihilating in gaseous NH3, in NH3–Ar and NH3–Ne gas mixtures, and in liquid NH3 have been measured as a function of density and temperature. The annihilation rate of slow positrons in NH3 gas, λNH3, has a strong nonlinear dependence on gas density and temperature, indicating a complex positron‐ammonia interaction. A Zeff/Z ratio of 1860 was observed for 22.5°C NH3 gas at 2.4×10−4 g/cm3. Above gas densities of about 0.0015 g/cm3 at 22.5°C, λNH3 is found to be equal to the value measured in liquid NH3 at 0.607 g/cm3. λNH3 is additionally found to be independent of the partial density of Ar or Ne in the gas mixtures. 1Zeff for orthopositronium annihilation in NH3 has a temperature independent value of 0.60±0.03 throughout the gaseous and liquid density range investigated.

This publication has 17 references indexed in Scilit: