present report describes a Windows based computer program called PALSfit3. The purpose
of the program is to carry out analyses of spectra that have been measured by
positron annihilation lifetime spectroscopy (PALS). PALSfit3 is based on the
well tested PATFIT and PALS fit programs, which have been used extensively by
the positron annihilation community. The present document describes the mathematical foundation of the PALSfit3 model
as well as a number of features of the program. The cornerstones of PALSfit3 are
two least squares fitting modules: POSITRONFIT and RESOLUTIONFIT. In both modules a model function will be fitted to a
measured lifetime spectrum. This model function consists of a function representing the physics
of the positron decay which is convoluted with the experimental time resolution function, plus a constant
background. The ‘physics function’
consists of a sum of decaying exponentials each of which may be broadened by
convolution with a log -normal lifetime distribution. The time resolution
function is described by a sum of Gaussians which may be displaced with respect
to each other. Various types of constraints may be imposed on the fitting parameters.
In the POSITRONFIT module, the fitting parameters to be extracted from a
measured spectrum are for each lifetime component its mean lifetime and its
broadening as well as its intensity. A correction for positrons annihilating
outside the sample can be made as part of the analysis. In the RESOLUTIONFIT module, parameters determining the shape of the time
resolution function can be fitted. The extracted resolution function may then
be used in POSITRONFIT.
Graphics displays are provided to ease the selection
of some of the input parameters and to display results of spectrum analysis.
The results are also available in a text window.
PALSfit3 is verified on Windows XP and Windows 7, 8
The PALSfit3 software can be acquired from the Technical University of