On the Photoabsorption Cross Section of Uranium Metal

Abstract

The total photoionization cross section for uranium has been calculated in the energy range 60-540 eV using a local-density based random phase approximation (LDRPA). The result is compared t o compilations of experimental photoabsorption data and is found to clear up a number of discrepancies between experiment and other calculations in the region between onset of 5d-and 4f-absorption.

Characterization of optical constants for uranium from 10 to 47 nm

“…Our measured optical constants for uranium are consistent with [8] and Cukier et al [9]. Also shown are optical constants for uranium determined by Henke et al [10] based on theoretical calculations [11][12][13]. the reflectance performance of a multilayer mirror coating created for the IMAGE satellite (see Fig.…”

“…To our knowledge, this is the first time the optical constants of elemental uranium have been measured in this wavelength range. We find that the measured constants differ significantly from theoretical values [10][11][12][13] referenced on the Center for X-Ray Optics (CXRO) website [16]. The revised constants would have significantly aided in the design of the IMAGE mirror [1] and resolve discrepancies in the previous study between multilayer designs and the measured reflectance data [17].…”

“…Figure 5 also shows the theoretical optical constants for uranium estimated by Henke et al and cited on the CXRO website [10,16]. These constants are based on theoretical calculations of the photoabsorption cross section of uranium [11][12][13]. Previous to our study, these calculations were the only optical constants for uranium available in this region.…”

“…These multilayers were designed using theoretical estimates for the optical constants of uranium at the design wavelengths [10][11][12][13]. However, the fabricated mirrors reflected differently from what was predicted, which raised questions about the accuracy of these theoretical values.…”

Resonances in Near-Threshold X-Ray Photoabsorption of Inner Shells

“…The process could proceed as a 5d-5f absorption, followed by an autoionizing decay; or as a 5f-eg absorption, strongly modified by interchannel coupling with the 5d-5f transitions. Owing to the open f-subshell, there are a myriad of possible optically allowed 5d"5f final multiplets; the strength of the interactions between these multiplets makes the calculations very difficult because many-body effects are so important [6]. Furthermore, the fact that the experiment was performed on a solid, while the calculation was done for a free atom, could lead to some discrepancies.…”