AN EMPIRICAL CORRECTION FOR ABSORPTION ANISOTROPY

A least-squares procedure is described for modeling an empirical transmission surface as sampled by multiple symmetry-equivalent and/or azimuth rotation-equivalent intensity measurements. The fitting functions are sums of real spherical harmonic functions of even order, y(lm)(-u(0)) + y(lm)(u(1)), 2 less than or equal to l = 2n less than or equal to 8. The arguments of the functions are the components of unit direction vectors, -u(0) for the reverse incident beam and u(1) for the scattered beam, referred to crystal-fixed Cartesian axes. The procedure has been checked by calculations against standard absorption test data.