• Ashwini Kumar

      Articles written in Pramana – Journal of Physics

    • Doping and bond length contributions to Mn K-edge shift in La$_{1-x}$Sr$_{x}$MnO3 ($x=0-0.7$) and their correlation with electrical transport properties

      S K Pandey R Bindu Ashwini Kumar S Khalid A V Pimpale

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      The room temperature experimental Mn K-edge X-ray absorption spectra of La$_{1-x}$Sr$_{x}$MnO3 ($x = 0-0.7$) are compared with the band structure calculations using spin polarized density functional theory. It is explicitly shown that the observed shift in the energy of Mn K-edge on substitution of divalent Sr on trivalent La sites corresponds to the shift in the center of gravity of the unoccupied Mn $4p$-band contributing to the Mn K-absorption edge region. This correspondence is then used to separate the doping and size contributions to the edge shift due to variation in the number of electrons in valence band and Mn-O bond lengths, respectively, when Sr is doped into LaMnO3. Such separation is helpful to find the localization behaviour of charge carriers and to understand the observed transport properties of these compounds.

    • Systematic study of multiparticle production in nucleus–nucleus interactions at 14.6 A GeV

      Ashwini Kumar G Singh B K Singh

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      An experimental analysis of 855 events induced by 14.6 A GeV $^{28}$Si in nuclear emulsion is presented. Mean multiplicities of charged secondary particles produced in the nuclear interactions are studied and compared with the results from the other experiments for the same projectile at 3.7 A GeV as well as data for proton at similar energy (14 GeV). An analysis of pseudorapidity densities of target fragments (black and grey particles) is also performed. The behaviour of the KNO scaling law of the multiplicity distribution for shower particles has been examined. In order to accumulate knowledge about the intermittent behaviour of shower particles, the scaled factorial moments (SFMs) are computed in $\eta$-space and $\phi$-space for a set of data in the $^{28}$Si–AgBr events. Furthermore, validity of limiting fragmentation of shower particles produced in central collision events induced by $^{28}$Si-emulsion interactions has been tested. A crude estimation for the energy density of the nuclear matter formed in the central collision events at our energy has been examined.

    • Characteristics of disintegration of different emulsion nuclei by relativistic 28Si nuclei at 3.7 A GeV

      Ashwini Kumar A Prakash Ashok Kumar R K Jain B K Singh

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      An analysis of the data based on 924 inelastic interaction events induced by 28 Si nuclei in a nuclear emulsion is presented. The nuclear fragmentation process is studied by analysing the total charge (𝑄) distribution of the projectile spectators for different emulsion target groups along with the comparison of Monte Carlo Glauber model results. Probability distributions for total disintegrated events as a function of different projectile masses are shown and compared with cascade evaporation model results at same energy per nucleon. Further, mean multiplicities of different charged secondaries for different classes of events are presented and for each event, variation of mean multiplicities as a function of total charge (𝑄) is also presented. The pseudorapidity distributions and normalized pseudorapidity distributions of the produced charged particles in nucleus–nucleus collisions at 3.7 A GeV are analysed for total disintegration (TD) as well as minimum-bias events.

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