Self-absorption of Mβ photons across the M5 edge for elements with 70 ≤ Z ≤ 80

J TRINCAVELLI; A CARRERAS; M TORRES DELUIGI; C. C. MONTANARI; D. M. MITNIK; S.P. LIMANDRI; S. SEGUI; G CASTELLANO

Toyama

Congreso; 26th International Conference on Ion Beam Analysis y 18th International Conference on Particle Induced X-ray Emission; 2023

IBA&PIXE

X-ray attenuation in matter is involved in many areasranging from radiation therapies to materialscharacterization by means of spectroscopical techniques.For elements with atomic number Z in the range 70 < Z< 78, the literature reports that the M emission energy(M4N6 decay) slightly exceeds the M5 binding energyEM5 [1], which implies a strong self-absorption of thesecharacteristic x-rays when traversing the sample pathtowards the detector.In a recent study [2], the description of the Mβself-absorption in pure Re and Os targets has shown todepend critically on the EM5 value, as well as on the massabsorption coefficient (μ) jump ratio across this edge.With this motivation, in the present work WDS purespectra induced by 20 keV electrons have been acquiredin an SEM to survey the bremsstrahlung absorptionaround the M5 edge. Figure 1 shows a Re spectrum alongwith two fitting curves using values given in ref. [3] andconsidering different choices for EM5. Clearly, thepredicted background contribution is not suitable whenusing the value reported in ref. [1]. A better spectralfitting is attained when the M5 edge is shifted around 26eV towards higher energies.Fully relativistic calculations implemented by using theHULLAC suite [4] have been performed for solving themany-electron Dirac equation, to provide an estimate forthe configuration energy associated with M5 one-vacancystates. The obtained results are in good agreement withthe experimental determination of EM5 values.