The Absorption of X-Rays of Wave-Length50≤λ<150X.U. by Elements of Low Atomic Number

With a 600 kv x-ray source and a two-crystal spectrometer especially designed for short wave-length x-rays, the mass absorption coefficients for C(6), Na(11), Al(13), S(16), K(19), Ni(28), Cu(29) were determined for wavelengths from 50 to 209 X.U. A small $\delta \lambda$ interval was used. The results are estimated to be in error by no more than two percent. The present results are compared with the few overlapping measurements of other observers. The values of the electronic scattering coefficient predicted by the Klein-Nishina formula are in excellent agreement with the experimental values of the scattering by carbon in the region $40\le \lambda \le 100$ X.U., which confirms the Klein-Nishina formula for this wave-length region. The photoelectric absorption in copper was found to be proportional to ${\lambda }^{2.83}$.