PLRF Code for Decomposition of Positron Lifetime Spectra

Abstract

A new code PLRF (version 19) was developed for decomposition of positron lifetime spectra. The PLRF code is based on the least squares fitting of positron lifetime spectra and utilizes a minimization routine MINUIT from the ROOT package developed at CERN. Multiple positron lifetime spectra can be fitted simultaneously using the PLRF code. Each fitting parameter can be selected to be either common (i.e., the same value for all spectra) or individual (i.e., different values for each spectrum). Positronium (Ps) contribution is considered as a double exponential component consisting of short lived para-positronium (p-Ps) and long lived ortho-positronium (o-Ps) component. Ratio of o-Ps and p-Ps contribution can be constrained. Several models were implemented into the PLRF code: independent exponential components, simple trapping model, and diffusion trapping model. Physically relevant parameters of the model are varied to get best agreement with experimental positron lifetime spectra. As a consequence the user obtains physically meaningful parameters from fitting, e.g., positron trapping rates in the case of the simple trapping model, grain or cell size and dislocation density in the case of the diffusion trapping model, etc.