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Peak Lists and Tables

Peak Lists and Tables

Displaying/hiding peak lists

Each spectrum always has at least one peak list associated with it. But you can have multiple peak lists per spectrum if you wish. When you first open a spectrum in a Spectrum Display all peak lists are shown by default. You can hide or show peak lists by right-clicking on the spectrum in the Spectrum Toolbar and going to the Peak List submenu.

Changing the colours of peak symbols and labels

In order to differentiate your peak lists more easily, you can change the colour of the peak symbols and peak labels of each peak list. Double-click on a peak list in the sidebar to bring up the Peak List Properties dialog box and select your preferred colours.

Peak tables

You can drag a peak list from the sidebar into the drop area in order to open it as a Peak Table. Alternatively, you can open a Peak Table module by going to View / Peak Table or typing PT. You can change the peak list shown in the table using the drop-down menu at the top. Selecting a peak in the table will also select it in any Spectrum Display where the peak is shown. Similarly, peaks selected in a spectrum will be shown as selected in the Peak Table. Use Ctrl (Cmd on a Mac) to select multiple peaks in a table using the mouse, or Shift to select sequential peaks. Ctrl/Cmd + A will select all peaks. Double-clicking on a peak in the table will centre all Spectrum Displays containing the peak on that peak.

Line widths and volumes

When placing peaks manually, there is no line width associated with them in the peak table. Snapping peaks to the nearest extremum using the SE shortcut will add a line width based on a parabolic fit. Re-fitting a peak with RP (or re-fitting several peaks together using RG) executes a Gaussian fitting procedure and also provides line widths. When you pick peaks by left-dragging the mouse while holding down Shift + Ctrl/Cmd you can choose whether to use the parabolic or gaussian fitting procedure in Project / Preferences (Ctrl/Cmd+,). Volumes can be added by estimating the volumes of peaks with EV.

Merit values

Each peak has a Merit value associated with it. This can take on any value between 0 and 1. It effectively acts as a weighting value for the calculation of chemical shifts. (Chemical shifts are reported as averages over all peaks contributing to the chemical shift of that nucleus). Peaks with a Merit value of 0 will not contribute to the chemical shift at all, those with Merit 0.5 only half as much as peaks with a Merit value of 1 etc. In addition, it is possible to set a threshold value below which peaks are coloured in a different colour. Double-click on a peak list in the sidebar to bring up the Peak List Properties dialog box. Select Use Merit Threshold, set the threshold value and choose a peak colour for the peak symbols and labels. This can be a useful way of marking peaks such as MAS side-band peaks.