• Volume 6, Issue 1

      January 1976,   pages  1-58

    • Calculations of anharmonic phonon relaxation times

      G P Srivastava

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      Anharmonic phonon relaxation times in Ge are calculated using (i) an isotropic continuum model, and (ii) a dispersive model. A complete spectrum of calculated results is presented. Frequency-averaged values for normal- and umklapp-three-phonon relaxation times are also calculated. A comparison is made between our findings and some earlier works, and disagreements are discussed. The results are applied in calculating some results in the theory of lattice thermal conductivity.

    • A note on the elastic constants of sodium bromate from 350 K to 77 K

      K R Srinivasan E S R Gopal

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      The elastic constantsC11,C12 andC44 of sodium bromate single crystals have been evaluated using 10 MHz ultrasonic pulse echo superposition technique. The values areC11=5.578,C12=1.075,C44=1.510 (×1010 N/m2) at 290 K and 6.35, 1.98 and 1.65 (×1010 N/m2) at 77 K. The present room temperature values agree closely with the recent values of Gluyaset al. but the other earlier measurements show some scatter. A comparison between the elastic constants of sodium bromate and sodium chlorate is also made.

    • Carbon phosphide (B2Σ+ — A2Πi) band system: RKR Franck-Condon factors andr-centroids

      N Sreedhara Murthy L Siddarame Gowda B Narasimhamurthy

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      Franck-Condon factors andr-centroids based on Rydberg-Klein-Rees potential have been computed for the CP (B2Σ+A2Πi) band system. These results are compared with the Morse values and discussed.

    • Radiative decays, photoproduction and total cross section of theψ particles

      K (xxxV) L Sarma G Rajasekaran J Pasupathy

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      It is pointed out that the coupling characterizing theψ-γ vertex must change substantially between the limits,ψ on mass-shell which occurs inψe+e and photon on mass-shell which is relevant in radiative decays likeψππγ, ψηγ and photoproduction ofψ. This has the consequence that the value ofψN total cross section must be larger than what is inferred from the use of naive vector dominance in photoproduction.

    • Some neutral current effects in an SU(3)×U(1) gauge model

      K Maharana C V Sastry

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      The anomalous magnetic moment of muon is calculated in anSU(3)×U(1) gauge model proposed by Gupta and Mani. We find the contribution due to the intermediate gauge bosons to be of the same order of magnitude as in Weinberg. Salam model. The deep-inelastic structure functions are also analysed in the same model and inequalities for the structure functions are obtained in the light-cone algebra approach.

    • Multi-band spectra of odd and even nuclei of the s-d shell

      Jyoti K Parikh

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      The energy levels of21, 23Na,22, 23Ne,24, 28Mg and25, 29Al are obtained by mixing various bands using the projected deformed Hartree-Fock (DHF) method. Solutions having minimum energies are found to be prolate for all the nuclei considered here. Higher bands are obtained either by considering particle-hole excitations or oblate solutions. These various bands are mixed using the projection method and care has been taken to orthogonalize the bands. The interactions used in this study are those given by Kuo, Preedom-Wildenthal (PW) and WHMK interactions. The last one seems to give good results for most of the nuclei considered here. Not only are the lowest bands well-reproduced but the second lowest bands agree reasonably well in most nuclei. The third lowest ones obtained in some nuclei are not yet observed as complete bands. However, K obtained for the third band seems to be correct. A comparison with shell model calculations—which are numerically exhausting—shows similar results for the lowest band. However, the agreement of the second band varies from nucleus to nucleus. A comparison between matrix elements of the interactions is made to analyze the results.

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