Measurements of M-shell fluorescence yields and Coster–Kronig transition probabilities for Bi and Th employing synchrotron radiation-induced selective photoionization

Abstract

In the present work, M-shell fluorescence yields (ω₃, ω₄ and ω₅) and Coster–Kronig (CK) transition probabilities (f₄₅, f₃₄, f₃₅, f₂₃, f₂₄, and f₂₅) were determined for Bi (Z = 83) and Th (Z = 90) using synchrotron radiation energies tuned across the M_i (i = 1–5) sub-shell absorption edges in the energy range of 2.5–5.2 keV. For both elements, two sets of fluorescence yields and Coster–Kronig transition probabilities were experimentally evaluated by employing M-shell photoionization cross sections (PCSs) based on the relativistic Hartree–Fock–Slater (HFS) model tabulated by Scofield and the self-consistent Dirac–Hartree–Fock (DHF) model tabulated by Chantler. The present measured ω_i and f_ij values have been compared with two sets of theoretical values based on the non-relativistic Hartree–Slater (NRHS) calculations employing the Hermann–Skillman potential reported by McGuire (1972) and the Dirac–Hartree–Slater (DHS) model predictions reported by Chauhan and Puri (2008) to assess the validity of theoretical approaches. The present work provides new experimental benchmarks for M-shell fluorescence yields and Coster–Kronig transition probabilities, addressing the existing gaps in atomic databases.