Programs in Physics & Physical Chemistry
|[Licence| Download | E-mail| New Version Template] aagk_v1_0.gz(15 Kbytes)|
|Manuscript Title: POSITRONFIT: a versatile program for analysing positron lifetime spectra.|
|Authors: P. Kirkegaard, M. Eldrup|
|Program title: POSITRONFIT|
|Catalogue identifier: AAGK_v1_0|
Distribution format: gz
|Journal reference: Comput. Phys. Commun. 3(1972)240|
|Programming language: Fortran.|
|Operating system: B6700 MCP MARK II.00.|
|RAM: 20K words|
|Word size: 48|
|Keywords: Atomic physics, Positron, Lifetime, Source correction, Least squares, Fitting, Convolution, Minimization, Sum-of-exponentials, Iterations, Marquardt, Constraints, Covariance matrix, Solid state physics, Experiment.|
|Classification: 2.3, 7.4.|
|AAGX_v1_0||POSITRONFIT EXTENDED||CPC 7(1974)401|
|AAHI_v1_0||INTERACTIVE POSITRONFIT||CPC 15(1978)97|
Nature of problem:
In a condensed material positrons may annihilate at several different characteristic rates. A measured positron lifetime spectrum will therefore consist of a sum of decaying exponential functions with different decay rates, smeared somewhat owing to the finite time resolution of the measuring system and superimposed on a constant background.
Positron lifetime spectra are analysed by an iterative least-squares technique of the semi-linear Marquardt type. The mathematical model is a sum of decaying expotentials convoluted with a gaussian resolution function, and with a constant background added. Fixed values can be imposed on any number of lifetimes and relative intensities. Correction for the source annihilation is taken into account. A statistical analysis is made resulting in the covariance matrix of the estimated parameters.
The program in its present version is restriced to include up to four lifetime components. The maximum number of channels in the multichannel analyser is 512, and of these max. 400 are used in the analysis.
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