The 1 st Cumulant or moment (a 1) is used to calculate the intensity weighted Z average mean size and the 2 nd moment (a 2) is used to calculate a parameter defined as the polydispersity index (PdI). It is important to note here, that the Cumulants analysis algorithm does not yield a distribution â it gives only the intensity weighted Z average and the polydispersity index.
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