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Manuscript Title: ERIKA: a program for the decomposition of line spectra.
Authors: M. Rysavy, M. Fiser
Program title: ERIKA
Catalogue identifier: ACEH_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 29(1983)171
Programming language: Fortran.
Computer: ES 1040.
Operating system: OS/21.8F - MVT.
RAM: 80K words
Word size: 8
Keywords: General purpose, Spectroscopy, Experimental data, Lsq method, Minimization, Simplex method, Internal conversion, Auger effect.
Classification: 4.9.

Nature of problem:
After having measured a real line spectrum, it is necessary to decompose it into particular lines. The present program performs this task and supplies the positions and heights of all peaks.

Solution method:
Every line is described by an analytic function depending on several parameters (height, position and shape parameters). The optimum values of these parameters are determined by the minimization of the function x**2 using the simplex minimization method. Moreover, a background which may also be a function of several parameters is fitted, as well.

Restrictions:
In the present version, the program is suitable for the decomposition of the internal conversion spectra. To apply it to spectra of different types, the line shape should probably be modified (see long write-up for details). A maximum of 20 parameters can be used. The spectrum to be decomposed must be given in no more than 150 points.

Running time:
The running time depends on the number of parameters fitted. The test run needed ~~ 8.5 min of CPU time.