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                Robfit uses the code stgen to create a standard made up of back to back cubic splines.  It included the ability to make these fit Gaussian, Laurentzian, and Voigt peaks which are a convolution of a Gaussian and a Voigt.  In addition it includes the ability to any peak in the actual spectrum as a standard.  These standards had variable widths, locations and heights. 

Templfit fits gamma ray spectra in which the rays are assumed to travel through material that results in a strengthening of the low energy side of the peak.  The peak shape in this case is generated by pkpolym.for.  This code has a skew and jump that allow the peak shape to be varied in the process of fitting the peak.  In templfit the skew and jump are fitted to Pade approximates, so that they are not independent for all energies.  In peakfit they can be varied individually for each peak.  The line in code is

CALL PKPOLM(X,ASKEW,AJUMPV,PX,PSKEW,PJUMP,PEAK)

The values of X, Askew, and Ajump are inputs.  The value of f_A is shown below.  The terms px, pskew and pjump (¶Peak/¶X, ¶Peak/¶askew, ¶Peak/¶ajump) are return values generated inside the subroutine.

                         

 

 

This function without the jump is in the book [Klaus Debertin and Richard G. Helmer, Gamma- and x-ray spectrometry with semiconductor detectors, Elsevier Science Pub. Co., 1988 - Table 3.2 on page 164].

The code TPKPOLY.for (tpkpoly.wpj) begi ns with a section for testing the derivatives, then continues to generate pkpol.grf for the first picture in which the skews are varied and pkpol2.grf for the second picture in which the jumps are varied.  The zips contain the codes used to produce these two pictures.

The background is set to drop linearly from 100 to 10 across the region.  The jump is zero.  The small skew values are the highest.  Negative values of skew diverge.  Skews.zip

                The Jump has a more rounded bottom than the skew.  The skew of 1 should be the same as in the figure above.  jumps.zip