SSA Simple Scan Analsis

The command produces some estimates of peak parameters ( originally coded by T. Schmidt).

Format:

SPECTRA> ssa scan_id

Description:

The following symbols are created:

SSA_CMS
SSA_FWHM
SSA_MIDPOINT between those points which are at 50% of the peak
SSA_INT integral
SSA_PREC no. of significant digits of the results
SSA_PEAK_X x-coord. of the highest point
SSA_PEAK_Y y-coord. of the highest point
SSA_A_BACK bg = ax + b
SSA_B_BACK
SSA_STATUS 1 for successful completion SSA_REASON 0: ok, 1: np < 6, 2: stbr, 3: no y(i) > 0., 4, 5: midpoint calc, 6: max outside x-range

The parameters are calculated after a linear background has been subtracted.

/nbg=np

np points on the left and on the right side are used to determine the linear background fit.

The default of np is 10% of the data points but it is required to be in the range [2,20].

/nob$*$ackground_subtraction

There is no background subtraction before the peak parameters are calculated.

/nodisplay

Suppresses the display of the result.

/stbr=val

The required signal to background ratio (def. 3). SSA_STATUS is zero, if the signal is not STBR times above the background.

/text

A TEXT GQE is created that contains the SSA results.

/x_mi$*$n=val

/x_ma$*$x=val

The SSA is calculated for the points which are inside these limits.

e.g.:

The output of the following example can be found in section 15.3.71.

!
! Example for SSA, simple scan analysis
!
 crea test -5 5 100
 calc test = 10*exp(-test*test) + random(test)
 ssa 1
 del 1.3 1.4
 display
 post/eps ssa_example.ps

Figure 15.9: Example for SSA, code in sec. 15.3.71