X-Ray Absorption Coefficients of Thorium, Uranium, and Plutonium—Experimental Determination and Theoretical Interpretation

The x-ray absorption coefficients of thorium, uranium, and plutonium have been determined for the Kα and Kβ radiations of silver, molybdenum, copper, cobalt, iron, and chromium. Four absorption edges were found in the wavelength region covered. These were identified as the LI, LII, LIII, MI, edges and a MI, MII complex for plutonium. There is considerable disagreement between the experimental coefficients and the theoretical coefficients obtained from the Internationale Tabellen. Reasons for this discrepancy are discussed briefly. A correlation is obtained between the absorption of x-ray energy and the number of electrons in the $5f$ shell.Through a consideration of the atomic number, a screening constant, principal quantum numbers, and the atomic energy levels for thorium, uranium, and plutonium, the x-ray absorption coefficients of these elements have been calculated. Screening constants and quantum conditions in the various equations were adjusted until, on the average, the experimental and calculated values agree within 2%. An increase in the screening constant of plutonium over that for thorium and uranium is interpreted in terms of the number of electrons occurring in the $5f$ shell. The change in certain quantum conditions for plutonium in comparison to those for thorium and uranium is interpreted in terms of plutonium being a subtransitional point within the $5f$ transition series.