The most important part of the raw data processing is the searching for diffraction peaks, since the peak positions and intensities are the actual input to the search-match calculation (i.e. the qualitative phase analysis). Match! uses the well-known second-derivative method to perform this task.
The peak searching can be carried out manually by selecting the "Peak search" command from the "Pattern" menu (or using the corresponding button ), or implicitly during the automatic raw data processing. Alternatively, a special peak search is also carried out automatically if the profile fitting command is executed without any peak data present. As a result, the profile fitting can be used as an alternative to the normal peak searching, both manually as well as during the automatic raw data processing.
If you a mixed wavelength (alpha 1 and 2) has been used in the diffraction experiment, you can activate the option "Add alpha2 peaks automatically" on the "Raw data" tab of the "Options" dialog (group "Peak searching"). If you activate it, Match! will explicitly add the alpha2-peaks during peak searching if a mixed (alpha1+2) wavelength is used, even if only the corresponding alpha1-peak is detected.
Before running the peak searching we strongly recommend to check and maybe correct the background. You should always keep in mind that if the background is too high in certain parts of the diffraction pattern, this may prohibit the detection of peaks in this area! You could e.g. try to reduce the background flexibility by pressing <Ctrl+F3> one or two times (<Cmd+F3> on the Mac).
If the raw diffraction data are very rugged, you could try to smooth your raw data before running the peak searching.
If you use the normal peak searching functionality, Match! will try to determine the FWHM (Full Width at Half Maximum) separately for each peak automatically. If this is not possible, it will use the corresponding default value (which can be adjusted in the "Automatic Raw Data Processing Options" dialog). If you would like to obtain more accurate FWHM values, you should use the profile fitting command instead of or after the peak searching.
Normally, the intensity values that are calculated during the peak searching procedure are integrated intensities, taking into account both the height as well as the FWHM of each peak. You can view the integrated intensity values in the peak list on the upper right-hand side. An exception to this is the relative intensity scaling of the vertical axis, in which case the integrated intensity values are scaled to a maximum value of 1000.0.
One task associated with peak searching is to decide which "hump" in the raw data corresponds to a Bragg peak and which is an artifact or noise. Obviously, there has to be a certain parameter "sensitivity" using which the software can make this decision.
When peak searching (in any variant just described) is carried out for the first time, a default sensitivity is used which takes the "noise" found in the raw diffraction data into account. This default sensitivity has been chosen to obtain good results with a large variety of diffraction patterns. However, it may nevertheless be necessary to adjust the sensitivity for your special data. Note that you can also modify the default peak search sensitivity values for peak searching and profile fitting separately in the "Automatic Raw Data Processing Options" dialog.