• Volume 31, Issue 3

      September 1988,   pages  169-240

    • A plausible explanation for muon events due to radiation from Cygnus X-3

      C Premkumar Yesudian

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      The muon events produced at Soudan-I and NUSEX proton decay detectors due to radiation from Cygnus X-3 are given a plausible explanation on the basis ofE6 GUT. The possibility of verifying the explanation by using the accelerator experiments is suggested.

    • Semi-classical approach to antiproton-nucleus scattering

      B Dey C S Shastry T K Roy

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      The similarities and differences between antiproton-nucleus scattering and heavyion-nucleus scattering are examined. It is found that the one-turning point approach viz Wentzel, Kramers and Brillouin (WKB) approximation can be applied to the analysis of antiproton-nucleus scattering. Using this approximation, a closed form expression for the nuclear phase shift is deduced from the corresponding expression for the heavy-ion scattering phase shift derived by Shastry and the method is illustrated by carrying out the cross-section calculation of$$\bar p + {}^{40}Ca$$ atElab = 46·8 MeV.

    • Development of high resolution silicon surface barrier detectors

      R P Sharma

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      Fabrication methods for silicon surface barrier detectors and their correlated properties which result in the production of high resolution (< 20 keV) devices have been studied. The techniques for fabrication and testing of the detectors currently employed at our Centre are presented. An FWHM of 14keV for 5·486 MeV241Am α has been achieved. Our results are therefore comparable with the best in the world.

    • Tracks of 18·56 MeV/u40Ar ions in Lexan polycarbonate detector

      Swarnali Ghosh Atul Saxena K K Dwivedi

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      Latent damage tracks of energetic40Ar ions (18·56 MeV/u) have been recorded in Lexan polycarbonate detector. Bulk and track-etch parameters are evaluated under successive chemical etching. Our results show a linear correlation between the measured track-etch rate along the track and the corresponding total energy-loss rate and predict a threshold value of 5·0 MeV mg−1 cm2 for track registration. Maximum etchable track lengths of40Ar ions as a function of energies have also been measured and compared with three different sets of theoretical ranges.

    • Amplified spontaneous emission from nitrogen laser pumped dye lasers

      M R Gorbal M I Savadatti

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      The nitrogen laser pumped dye laser output has been studied with emphasis on the behaviour of amplified spontaneous emission (ASE) with respect to the tuning wavelength, pump energy, dyes and their concentration and solvents. Spectral spread of ASE is narrower than fluorescence and its maximum is shifted towards the red side. However, lasing occurs beyond the ASE region. ASE is small at high gain wavelength and increases at the edges of the gain curve. Laser energy is highest at the ASE peak with minimum ASE present in the output. ASE is reduced with increased laser energy in the energy transfer dye lasers.

    • X-ray diffraction line profile from the aggregate of distorted crystallites. II

      G B Mitra T B Ghosh

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      An expression for the fourth moment of the line profile in terms of several strain derivatives and the possibility of measuring the ‘wavelength’ of crystal distortions (λ) for any sinusoidally varying component of the strain are available. The experimental means for evaluating such strain derivatives in the expression for the fourth moment was earlier described. A numerical method for evaluating this wavelength and its subsequent use to determineλ in several samples ofα-brass is presented here. The data used are taken from the earlier paper of the authors. An attempt has been made to interpret the values ofλ and their changes with cold working and annealing in terms of lattice strain.

    • X-ray determination of the mean Debye-Waller factors and Debye temperatures of KCl-RbCl mixed crystals

      K Srinivas D B Sirdeshmukh

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      Integrated intensities of Bragg reflections have been measured for KCl-RbCl mixed crystals with various compositions and the data used to evaluate the mean Debye-Waller factors and the Debye temperatures. The composition dependence of the Debye-Waller factor is highly nonlinear with positive deviations from linearity while that of the Debye temperature is slightly nonlinear with negative deviations from linearity. Using an empirical relationship between the Debye temperature and the molar volume, the average values of the Gruneisen parameter for some mixed crystal systems are obtained.

    • Compton profile study of α-manganese

      Anil Gupta B K Sharma B L Ahuja

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      The results of a Compton profile study on polycrystallineα-Mn are reported. Our measurement are compared with theoretical results computed for different 3d-4s electron configurations within the RFA model. Best agreement between the measured and calculated values is found for 3d5·44s1·6 configuration. Theoretical Compton profile ofγ-Mn calculated using the same procedure is close to that for bcc phase with similar electron configurations.

    • XANES and EXAFS in Cu-Ti and Ni-Zr glasses

      K B Garg K S Jerath H S Chauhan U Chandra R K Singhal K V R Rao

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      X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements have been done at the K-edge of Cu in Cu-Ti glasses and on the K-edges of Ni and Zr in Ni-Zr glasses using a synchrotron radiation source. The results are discussed in terms of the shape shift and intensity of the absorption edge as well as the principal absorption maximum. The values of bondlength calculated by the one-electron multiple scattering XANES theory as well as the graphical analysis EXAFS technique show good agreement.

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