X-RAY ABSORPTION IN THE 2-TO-200 A REGION

Physical and chemical analysis, x-ray astronomy and high temperature plasma diagnostics which utilize the ultrasoft x-radiations have made evident a strong need for filling the gap in measured absorption coefficient data for the radiations between the conventional x-rays and the extreme ultraviolet. More than one hundred new coefficients have been recently measured in this laboratory on the gas state, atomic or molecular, containing He, C, N, O, F, Ne, S, Cl, Ar, Kr, and Xe using eleven fluorescent, characteristic wavelengths Al-K 8.34 A through Be-K 113.8 A. The radiations were isolated by Bragg reflection from multilayer analyzers of the Langmuir-Blodgett type and by pulse height discriminating proportional counter intensity measurements. Using these data and data previously published, a complete table has been determined for He through Ar and for wavelengths below the L sub III edges and in the region 2-to- 200 A. Absorption cross sections have been calculated for many compound materials which are commonly encountered in low energy x-ray analysis. The transmission of x-rays from a source above the earth has been tabulated as a function of altitude and wavelength.