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Manuscript Title: A FORTRAN code for automatic spectrum analysis on medium-scale computers.
Authors: E.D. von Meerwall
Program title: PEAK2
Catalogue identifier: ABML_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 9(1975)351
Programming language: Fortran.
Computer: IBM 370/155.
Operating system: OS/MVT.
RAM: 14K words
Word size: 32
Keywords: Nuclear physics, Automatic peak detection, Additive convolution, Doublet resolution, Lorentzian fit, Gaussian fit, Gamma ray, Neutron activation, Infrared, Nuclear resonance, Particle size, General purpose, Fit, General experiment.
Classification: 4.9, 17.4.

Nature of problem:
The program performs fully automatic detection, description, and fitting of peaks (including doublets) in digital X-Y spectra of various kinds, given only an approximate width, and the choice of positive or negative (absorption) height, of the peaks.

Solution method:
Peak detection is performed by additive convolution with a zero-area function. The peak region just detected is conventionally described and its singlet or doublet nature decided. Gaussian or lorentzian peak region fit after background subtraction is performed; in the doublet case the fit is iterative. Spectral smoothing before, and plotting after, processing are vailable; spectra are processed automatically in a single pass. The emphasis on economic use of memory is retained.

Restrictions:
The dimensions, such as 1024 spectral points, and 100 peak regions (for plotting purposes only), are easily changed together with some prelimin- ary checks.

Unusual features:
Based on the methods described in Comp. Phys. Commun. 5(1973)309. the program is intended to be used either as it is, or as a basis for adaptation of its methods to spectral analysis on smaller computers and/ or in real time. The main attributes of the minicomputer code have been retained with many refinements. New features include a (non-essential plotting facility, regional linear variability of the expected peak fwhm, optional spectral (X) compression to reduce processing time, linear channel calibration (Xi=a+ib), and choices of positive and negative peak height, gaussian or lorentzian peak shape, and regionally constant Y-uncertainty or counting statistics.

Running time:
On an IBM 370/158 compilation (G) takes 18 CPU s, A 1024 channel spectrum with 30 peaks, including 18 doublets (fwhm ~=4 channels) is processed in 11 CPU seconds. A 256-channel Mossbauer 6-line calibration spectrum uses 4 CPU s.