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.