Articles written in Pramana – Journal of Physics

    • Study of photon-induced L3 vacancy alignment for elements La to U

      Ajay Sharma Meenu Singh Raj Mittal

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      Alignment of photon-induced L3 vacancies is studied in rare earth and highZ elements at energies of experimental interest, near thresholds to 60 keV, under nonrelativistic dipole approximation. Numerical calculations of the matrix element are undertaken to produce theoretical data for comparison with the experimental findings. The A2 values being s>0.1 at photoelectron energies <20 keV are certainly higher than 5–8% uncertainties quoted in experimental results. Present findings are from a very basic model, hydrogen-like and can further be treated as reference to observe the impact of screening, relativistic, multipole and retardation corrections to the model

    • L subshell fluorescent $X$-ray measurements to study $CK$ transitions in the $66\leqZ\leq83$ region


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      L subshell fluorescent X-rays in Dy, Ho, Er, Lu, Ta, W, Pt, Au, Hg, Pb and Bi have been measured using synchrotron with selective creation of electron vacancies in individual subshells. Coster--Kronig (CK) yields were derived from the measured intensities. Present measurements have been made at photon energies above the edges where differences between measured and theoretical attenuation coefficients are almost negligible. Parametric trends for the results with $Z$ were developed to cover all $Zs$ in the range of 66--83. The trends predict the switching-off of L1--L2, N1 transition at Z = 67. The extent of fall/rise of $f_Lij$ values corresponding to off/on of certain transitions is found inversely proportional to the difference in binding energies of two consecutive subshells involved in the transition. For $Zs$ above/below these rises/falls, $fL_13$ and $fL_12$ values are almost constants. $f_L23$ values involving no break at $Zs$ follow the general photoionization behaviour that ionization probability is highest at the edge energy and decreases with photon energy. Yield measurements with synchrotron radiation for Dy, Ho, Lu, Hg and Bi and experimental values for $f_L23$, $f_L12$ in Lu and for $f_L13$ in Ta are being quoted for the first time.

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