6.1.1 Enhancement effects

The Sherman formula describes the x-ray production for an element i caused by the primary excitation radiation. However, if there is a significant amount of other elements (let’s say j) in the sample, which characteristic emission lines have enough energy as to be able to excite the element i, then an enhancement of the intensity of the element i will be observed.

Shiraiwa and Fujino proposed in 1966 a correction to the Sherman formula by introducing an additional factor Σ_jw_jS_i,j taking into account the enhancement part:

where all of the symbols remain as previously explained, and

The enhancement effect becomes noticeable only when the elements j are present in large amounts, so calculating the additional correction Σ_jw_jS_i,j is only worth for some specific cases, such as metal alloys or samples with several elements having large concentrations (minerals, or other types of concentrates).

Reference: Shiraiwa, T.; Fujino, N. Theoretical calculation of fluorescent X-ray intensities in fluorescent X-ray spectrochemical analysis, Japan Journal of Applied Physics, Vol. 5 (1966) 886