Combining these three equations, the index of refraction in the oscillator model is given by
and expressing the numerical constants by r0 and using ω = ck = 2πc/λ yields
For typical x-raywavelengths (λ ≈ 1 Å) and electron densities of soft matter (ρe (H2O) = 0.334 Å−3) as well as ω ≫ ωr, the second term is much smaller than unity. Using the Taylor expansion yields the x-ray index of refraction
Note that by the above derivation, the index of refraction as a macroscopic quantity has been linked to the atomic phenomenon of scattering. The inherent ...