Compute the number of effective electrons using the Bethe f-sum rule.
The Bethe f-sum rule gives rise to two definitions of the effective number (see [Egerton2011]), neff1 and neff2:
This method computes and return both.
- nat (float) – Number of atoms (or molecules) per unit volume of the sample.
- cumulative (bool) – If False calculate the number of effective electrons up to the higher energy-loss of the spectrum. If True, calculate the number of effective electrons as a function of the energy-loss up to the higher energy-loss of the spectrum. True is only supported by SciPy newer than 0.13.2.
neff1, neff2 – Signal1D instances containing neff1 and neff2. The signal and navigation dimensions are the same as the current signal if cumulative is True, otherwise the signal dimension is 0 and the navigation dimension is the same as the current signal.
[Egerton2011] Ray Egerton, “Electron Energy-Loss
Spectroscopy in the Electron Microscope”, Springer-Verlag, 2011.