• N Singh

      Articles written in Pramana – Journal of Physics

    • Measurement ofL-shell photoelectric cross-sections in lower intermediateZ elements at 6 keV

      N Singh R Mittal K L Allawadhi B S Sood

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      L-shell photoelectric cross-sections have been measured at 6 keV for eight elements in the range 40⩽Z⩽53. The measurements agree with theoretical calculations.

    • Electron structure of interstitial hydrogen inα-Zr

      N Singh S P Singh S Mahajan V K Jindal S Prakash

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      The impurity-induced charge density in jellium is calculated by solving the Schrödinger equation self-consistently. The resulting phase shifts have been used to estimate the value of residual resistivity for dilute Zr-H system, which comes out to be 0.50 µΘ cm/at.%. An alternative form of one-parameter-screened Coulomb potential, which is more suitable than the customary Thomas-Fermi potential, is suggested. The calculated self-energy by using new potential is found close to its value obtained by Darbyet al.

    • Total attenuation cross-sections of fluorescent X-rays of Zr, Sn, Ba, Au, Pb, Th and U in elements 6⩽Z⩽82

      N Singh H S Aulakh K L Allawadhi B S Sood

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      The total attenuation cross-sections in elements 6⩽Z⩽82 forKα andKβ groups of lines of elements Zr, Sn and Ba andLl,Lα,Lβ andLγ groups of lines of the elements Au, Pb, Th and U have been measured. The experimentally measured attenuation cross-sections have been found in good agreement with the theoretical estimates.

    • Determination ofL-shell X-ray production cross-sections in holmium by 10–40 keV photons

      K S Mann K S Kahlon H S Aulakh N Singh R Mittal K L Allawadhi B S Sood

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      In an effort to resolve the existing discrepancy between experiment and theory, the cross-sections for the production ofLl,Lα,Lβ andLγ groups ofL-shell X-rays of Ho by photons of nine energies in the range 10–40 keV have been measured using an improved version of annular source double reflection geometrical set-up. Contrary to the earlier findings of Garget al that the measured values of the cross-sections are consistently higher than those calculated theoretically, the present results do not confirm this. The plausible deficiencies in the experiments of Garget al are pointed out and possible remedies to overcome them are suggested. It is concluded that the higher values obtained by Garget al are probably due to systematic errors in their method of measurement.

    • The elastic moduli, the volume contribution and the Cauchy ratio ford andf shell metals

      N Singh B S Yadav

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      The elastic constants of nine transition metals and four rare-earths and actinides are calculated using the ion-ion interaction defined by us recently. The volume contribution to elastic moduli is calculated by exploiting the density dependence of the screening function. The calculated volume contribution to bulk modulus is found to vary between 17.1% and 62.4% for a number of metals, which is quite significant and play an important role for describing quantitatively the violation of the Cauchy ratio for these metals.

    • Activation energy of hydrogen in Lu

      N Singh B Kumar

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      The impurity induced charge density is calculated in jellium by solving the Schrödinger equation self-consistently following the procedure of Manninen and Nieminen and using Kohn-Sham density functional formalism. The host-ion contribution is included through the spherical solid model potential (SSMP). The calculated activation energy 0.27 eV is found in good agreement with experimental value 0.28±0.02 eV. The estimated residual resistivity 1.02 µΩ cm/at% for Lu-H system using the resulting phase shifts agrees reasonably well with the observed value 1.75±0.10 µΩ cm/at%. The calculated configurational energy shows that hydrogen prefers tetrahedral(T)-sites over octahedral(O)-sites in Lu matrix. This has been confirmed by Bonnet experimentally. A very shallow value ofs-type bound state of energy −0.00316 Ryd predicts that there is no formation of lutetium hydride solution and H+ exists as a free ion in Lu matrix.

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