Attenuation of X rays in interstellar space.

Calculation of the X-ray interaction cross sections for three cosmic mixtures over the range from 1 keV (12.4 A) to 1.5 MeV (0.008 A). The cosmic composition of elements as given by Aller and utilized by Bell and Kingston (1967) and the total photon interaction cross sections per atom of the elements as computed by Hubbell and collaborators are used for this purpose. The results are compared with a formula given by Heiles (1971). Approximate agreement exists between 10 to 20 keV.