The basis of the peak insertion is the residual, the fitting algorithm seeks for typical shapes of peaks and double peaks.
Sometimes this automatic peak insertion is not successful because in complex multiplets the insertion of a new peak does not always reduce immediately the fit's Chi-squared value.
In these cases a significant difference is shown in the residual window, requiring manual inserting of peaks.
“Refit with auto peak insertion” tool performs a re-fit of the clicked region with a newly added peak, whose position is determined automatically by HyperLab. It is possible that this tool does not result is inserting a new peak, if the fit became worse than before. In this case only manually forced peak insertion may help.
“Manual peak insertion” tool requires you to click at a specific channel where the new peak should be inserted. HyperLab always tries to keep your new peak, even if the fit became worse than before. There is one case, however, when even manual peak addition is canceled: if the peak proves to be non-significant after the re-fit, that is, its amplitude is too small in absolute value; too small compared to the background or to the amplitude uncertainty; or the peak slips too close to another peak.
After clicking at channel 277 with the manual peak insertion tool, a new peak is inserted there and a re-fit is performed. The manually specified peak position is not hold fixed, but fitted by HyperLab's nonlinear minimizer in the usual way.
Please note that the residual has become significantly smoother, and the peaks have disappeared from it – but a closer look may reveal that possibly another peak may be added at channel 291.