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Analyses of spectra




The original N-procedure transforms the experimental spectrum Y(x) according to the equation


Y(x,p,Dx) = Y(x) - p[Y(x + Dx) + Y(x - Dx)].


Here, Y is the count rate (intensity), x is the number of current channel in the spectrum (running from 1 to N).


p = 2 (-2 - d2 + (d4 + 5 d2 + 4)1/2)/ d2, where


d = 2Dx/G,


Dx and G (in channels) are the procedure parameters.


The values of procedure parameters Dx and G are selected in order to obtain optimum resolution after the transformation at an appropriate signal-to-noise ratio. In the principle, one gets the best results, if the value of G is close to the experimental half width G for the narrowest component in the initial spectrum to be distinguished. The Dx value is close to value of G/2 (or less) while the signal-to-nose ratio is appropriate. The less is the Dx value, the better is the resolution, but the more we lose in the signal-to-nose ratio.


As the result one gets a derived N-spectrum with a better spectral resolution as it consists of narrower lines, the line position and the relative absorption area of every spectral component remaining unchanged.


The very broaden components and various absorption distributions lose in their amplitudes much more in the N-spectrum, than narrow spectroscopic lines. It permits to reduce their influence on the narrow spectroscopic components.


In general, the N-procedure improves the visual spectral resolution up to about 2-3 times at the expense of signal-to-noise ratio. The fitting results (for overlapping spectral components) are characterized by lower global correlation factors, if the N-transformed spectrum is used.