A reconsideration of the Goertzel-Greuling approximation for anisotropic scattering

To take anisotropic scattering effects into consideration, an approximate differential equation which relates the current to the current slowing down density is rederived using the Goertzel-Greuling approximation. As expected on physical grounds, the coefficient of the lethargy derivative of the current slowing down density is shown to vanish as the mass number of the scatterer tends to infinity in contrast to the original derivation where this coefficient grows unboundedly in absolute value as the mass number is increased