Analytic approximations to form factors

Analytical constants are presented which describe the magnetic form factors for the firstgroup transition elements, their ions, and some rare-earth ions. Functions which peak at sin θ/λ = 0 are represented by a function A exp (−ax²) +B exp (−bx²) + C, where x is sin θ/λ. Contributions such as (j₂) and (j₄) etc., which are zero at x = 0, are represented by [A exp (− ax²) + B exp (− bx²) + C]x². An estimate for the goodness of fit between the function and its analytic approximation is given for each case.