X-ray refractive index of silicon in the range 400 to 1100eV

Both the absorptive and dispersive parts of the silicon soft X-ray refractive index have been determined from grazing-incidence X-ray reflectivity measurements on bulk crystalline material using photons in the energy range 400-1100 eV. These values are in good agreement with semi-empirical values obtained from a self-consistent Kramers-Kronig approach applied to experimental data outside this energy range, and serve as a useful confirmation of the validity of these calculations within this important range of energies.