L X-ray intensity ratio measurements using selective L sub-shell photo-ionisation on synchrotron

L_α/L_ℓ, L_β /L_ℓ and L_γ/L_ℓ intensity ratios have been measured for elements in the range 66≤Z≤83 at tuned photon energies on synchrotron beam line-16 at Indus-2, India. For each element, three incident energies E_i were E₃; EL₃ < E₃ 2, E₂; EL₂ < E₂ 1 and E₁; E₁>EL₁ where EL_i are L_i absorption edge energies of the element. Emitted L X-ray spectrum of an element constitutes a number of X-ray lines generally grouped into four main groups due to limited resolution of available detectors as L_ℓ(L₃-M₁), L_α(L₃-M_4,5), L_β( L₁-M_2,3,4,5,N₄; L₂-M_3,4; L_3-N₁,_4,5,O_1,4,5) and L_γ(L_2-N₁,₄,O_1,4; L₁-N₂,_3,5,O_3,2). L_α and L_ℓ both comprise only the lines feeding L₃ level and L_β group comprises X-ray lines feeding all the three sub_-shells where as Lγ involves contribution from L₁ and L₂ feedings. Only E₃ excitation gives the ratios free from intra sub-shell Coster-Kronig (CK) transitions while excitations E₂ and E₁ give CK affected L_β/L_ℓ and L_γ/L_ℓ X-ray intensity ratios and L_α/L_ℓ still remains free from CKs. The pattern of intensity ratios at three excitation energies of elements was well interpreted in terms of on/off of CK transitions (; Campbell, 2003) and outer shell electron filling configuration (Scofield, 1973). - Highlights: • L_α/L_ℓ, L_β/L_ℓ and L_γ/L_ℓ intensity ratio measurements for selective sub-shell excitations on synchrotron. • Measured at 17 tuned energies with 0.5 keV interval on 11 elements in 66≤Z≤83 range. • Region 66≤Z≤83 involves sharp on/off probabilities of CK transitions and electron filling of 4f and 5d shells. • Interpreted the intensity ratio variations with Z in terms of CK transitions and outer shell electron configurations.