The intensity distribution and variance of the iron Kα multiplet

The variance of the Kα₁₂ doublet of iron X-radiation as a function of truncation range was determined using a silicon analysing crystal. The presence of satellite lines gives rise to an initial `pseudolinear' part to the variance–range curve; the origin and significance of this part are discussed. The effect of the satellite group was removed by interpolation of the line profile. The possibility of locating the background level by computation is investigated; it is shown that a mis-setting in the background level has an appreciable effect on the variance function, whilst a mis-setting in the background slope has negligible effect on the slope of the variance function. Results for both filtered and unfiltered radiation are given.