Vignetted photon fields, recharacterisation of V K alpha, and reducing X-ray uncertainties by a factor of two

A vignetting profile form is incorporated with characteristic X‐ray emission data from a Johann‐mounted crystal diffractometer. We prove the validity of the specific form of the vignetting profile. A new characterisation of the Kα profile for vanadium is presented, which supports and is superior to the current benchmark. Using the profile form as a correction for systematic vignetting reduces energy uncertainties by up to a factor of two or more. The greater precision in measurement robustness allows current atomic theories and profiles to be tested with higher levels of accuracy