Fine Structure Observed in Modified X-Ray Scattering by Boron

Using a double-crystal spectrometer, two portions of the spectrum of Cu $K{\alpha }_1$, $K{\alpha }_2$ radiation scattered by boron have been recorded. One portion is near the Rayleigh peaks; the other portion is at a distance of about 180 eV from the Rayleigh peaks. Several discontinuities have been noted in the first region. A definite double line has been observed in the second region at a distance from the Rayleigh lines which corresponds closely to the energy required for a $1s-2p$ electron transition. The widths of the observed lines are in agreement with the $K$ boron emission lines. No conclusive results have yet been obtained with regard to the selection rules. It is not clear that the process under investigation is a three-level transition process.