Same Side Off-Peaks
Beware of placing same-side off-peaks too close together if you are using a background type other than average, high only or low only (for example, the default: linear extrapolation). A large extrapolation can cause a very large error in the off-peak background correction if the background standard deviation is large and using a linear fit. The program will print a warning if it feels that the same-side off-peak extrapolation is excessive. In cases where the same side off-peak extrapolation is excessive, the user may want to select using the average of the off-peak counts. Of course, averaging the off-peak counts is really only applicable in situations where the background slope is zero.
For example, there may be some situations where interferences either above or below the peak require placing both off-peak background measurements on one side. There is nothing wrong with this, as long as "average" is used. A linear extrapolation in many situations, especially when the 2 positions are very close together, will produce an obviously
incorrect background model if the background standard deviation is large. The program will print a warning alerting the user to the possibility of possible incorrect background selection. Averaging the off-peak counts is applicable where the background (arithmetic) slope is zero (or equivalent to a "slope-factor" of 1.0).
There are a number of options to specify for the multi-point background acquisition. The number of points to iterate to and the background fit type (Linear or Polynomial) can be specified before or after the background intensity data has been acquired. Note that the sum of all multi-point intensities is automatically calculated and saved to the normal off-peak intensity arrays to so that normal off-peak background calculations can also be performed.