J.M. Sampaio

Relativistic calculations of M-shell decay rates and yields in Zn, Cd and Hg

In this work, we calculate the radiative and radiationless transition probabilities of M-shell vacancies in Zn, Cd and Hg atoms using the Dirac–Fock method. The obtained transition probability values are then used to calculate the corresponding fluorescence, Auger and Coster–Kronig yields for each subshell that are compared to existing theoretical calculations. Average M-shell fluorescence yields are derived and compared with semi-empirical and experimental results.

A novel portable energy dispersive X-ray fluorescence spectrometer with triaxial geometry

The X-ray fluorescence technique is a powerful analytical tool with a broad range of applications such as quality control, environmental contamination by heavy metals, cultural heritage, among others. For the first time, a portable energy dispersive X-ray fluorescence spectrometer was assembled, with orthogonal triaxial geometry between the X-ray tube, the secondary target, the sample and the detector. This geometry reduces the background of the measured spectra by reducing significantly the Bremsstrahlung produced in the tube through polarization in the secondary target and in the sample. Consequently, a practically monochromatic excitation energy is obtained. In this way, a better peak-background ratio is obtained compared to similar devices, improving the detection limits and leading to superior sensitivity. The performance of this setup is compared with the one of a benchtop setup with triaxial geometry and a portable setup with planar geometry. Two case studies are presented concerning the analysis of a 18th century paper document, and the bone remains of an individual buried in the early 19th century.

Relativistic calculation of K-, L- and M-shell x-ray fluorescence yields for Ba

A thorough survey of the literature has shown that fluorescence yields of barium are not well covered even though they are an element of major importance in electron beam ion trap (EBIT) devices. This work is meant to contribute towards filling in this gap by presenting new relativistic calculations for the K-, L- and M-shell fluorescence yields of barium, using the Dirac–Fock (DF) approach. Our results show good agreement with previous results for the K- and L-shells. There are no theoretical or experimental references for the M-shell, making these calculations the first ones performed for this shell.

Relativistic calculations of 1s22s2p level splitting in Be-like Kr

High-precision calculations of 1s22s2p excited energy levels in Be-like Kr isotopes are presented using the multi-configuration Dirac–Fock approach. The calculations include QED corrections and electron correlation including all single and double excitations up to n = 5 orbitals. Breit interaction and vacuum polarization were included to all orders in the self-consistent process. Effects of isotopic mass shifts and hyperfine corrections for 83Kr are discussed.

Relativistic calculations of atomic parameters in Ununoctium

K shell, and L and M subshells fluorescence and Coster-Kronig yields for the super-heavy element Uuo are calculated for the first time using the Dirac-Fock approach.

K-shell width, fluorescence yield, and Kβ/Kα intensity ratio calculation for Fe in the Dirac-Fock approach

K-shell fluorescence yield, width, and Kβ/Kα intensity ratio for Fe are calculated using the Dirac-Fock approach. Results are compared with available data.