Hi,

What type of curve should you fit to a PHA spectra (bias scan) - e.g. Gaussian, etc. So far split pearson 7 seems to work.

Ben

Hi Ben,

The distribution is usually described as "quasi-Gaussian," with

*σ* < √

*N*, where

*N* is the average number of primary ion pairs produced by an X-ray photon. Fano (1947, Physical Review 72:26-29) showed that

*σ* = √

*FN* = √

*FE*/

*ε*, where

*E* is the photon energy and

*ε* is the mean ionization energy of the counter gas. For argon, the "effective"

*F* is usually set at 0.8 and takes into account widening of the distribution due to secondary ionizations produced during avalanching. See Reed's "Electron Microprobe Analysis," 2nd ed., p. 86-87.

Brian