• Volume 6, Issue 5

      May 1976,   pages  259-328

    • Sum rules for the baryon20, baryon20′ and meson 16-plet coupling constants in broken SU (4) and SU (3) symmetry

      V Gupta

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      Sum rules for the coupling constants for D (20), B (20′) and P (16) are given taking into account first order breaking of SU (4) and SU (3) symmetries. The D (20) and B (20′) contain the usual 3/2+ baryon decuplet and 1/2+ baryon octet of SU (3), while the P (16) contains the usual pseudoscalar octet of pions, etc. These sum rules generalize the decuplet → octet + octet sum rules of broken SU (3 to a broken SU (4) symmetry scheme, in particular the charm SU (4) for hadrons. It is pointed out that, of the many sum rules, it may be possible to check some of them experimentally (see Section 5) and thus provide a test for an underlying SU (4 symmetry for strong interactions.

    • Production ofψ particles in N-N collisions and largePT phenomenon

      L K Chavda D S Narayan

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      We calculate the yield ofψ (3105) particles in N-N collisions in a model which associates the production of heavy particles with largePT phenomenon. Our results show thatψ (3105) has a fairly strong coupling to other hadrons. We propose a criterion in the search for charmed particles and a parametrization for the expected yields of such particles.

    • Dielectric properties of 4′-n-alkyl-4-cyanobiphenyls in their nematic phases

      B R Ratna R Shashidhar

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      The principal dielectric constants of the pentyl to octyl derivatives of 4′-n-alkyl-4-cyanobiphenyl have been measured as functions of temperature in their nematic and isotropic phases. All the compounds exhibit a strong positive dielectric anisotropy due to the presence of a large dipole moment along the major molecular axis. The principal dielectric constantsε andε as well as the anisotropy Δε decrease with increasing alkyl chain length. The experimental value of$$\bar \in = \frac{1}{3}$$ (ε+2ε) decreases with decreasing temperature, and is throughout less than the extrapolated isotropic value, in conformity with the model of antiferroelectric short range order proposed by Madhusudana and Chandrasekhar.

    • Mean spherical model-structure of liquid argon

      R V Gopala Rao T Nammalvar

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      A new formulation forS(k), the structure factor, has been obtained, treating the square-well potential as a perturbation on the hard-core in the mean spherical model approximation. The potential parameters have been varied not only to get a satisfactory peak height at the fitted temperature but also over a wide range of temperatures and densities. The agreement between the computed and experimental structure factor values shows that the representation of the attractive tail by a square-well potential yields a satisfactory method in understanding the structure of liquid argon.

    • Phonon spectra of Zn and Cd using a model pseudopotential approach

      O P Kulshrestha J C Upadhyaya

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      Recently Animalu has developed a model potential approach to study the electronic properties of transition metals. We have applied the transition metal model potential (TMMP) of Animalu in the local approximation to derive the phonon dispersion curves of Zn and Cd alongΓA,ΓM andΓKM symmetry directions. Our results differ widely from the experimental data. Further we have added the non-local contribution to the dynamical matrix following the scheme of Eschrig and Wonn and found the resuits comparable to the measured ones.

    • Stereochemical calculations on substituted benzene and benzene-like compounds

      Vasantha Pattabhi

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      Semi-empirical calculations have been done on hexaphenyl benzene, triphenyl benzene ands-triphenyl triazine free molecules and the results are compared with X-ray crystal structure studies. The conformation of isolated molecule differs from that found in crystals. The agreement improves when packing forces are also included in the minimum energy calculations.

    • Modification of Lytle’s theory: Interpretation of the extended fine structure associated with LIII absorption discontinuity of some ytterbium systems

      Pranawa Deshmukh Prabodhachandra Deshmukh Chintamani Mande

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      In Lytle’s theory for the extended fine structure in x-ray absorption spectra, the potential at the boundary of the ‘equivalent sphere’ around the absorbing atom, having volume equal to that of the Wigner-Seitz cell is considered to be infinite. It has been observed that Lytle’s theory is applicable only in the case of metals and metallic systems. In the present paper the extended fine structure associated with the LIII absorption spectra of some systems of ytterbium is interpreted on the basis of Lytle’s model, modified by using a finite potential instead of an infinite one at the boundary of the equivalent sphere. The values of this potential are estimated for eight systems of ytterbium. It has been shown that there exists a correlation between the potentials and covalency of the compounds.

    • Feynman diagram method for atomic collisions

      T Pradhan Avinash Khare

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      Feynman diagram method of treating atomic collision problems in perturbation theory is presented and matrix elements are calculated for a number of processes. The result for the resonant charge transfer in hydrogen is identical to the well known OBK value. However, in processes like collisional ionisation, the results are different from those obtained by conventional methods.

    • Intensity ratios of mesonic x-ray lines$$K_{\alpha _1 } , K_{\alpha _2 } $$ and$$L_{\alpha _1 } , L_{\beta _2 } $$

      T V Krishnan N A Narasimham

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      Intensity ratios ofμ-mesonic x-rays in some heavy elements are discussed. Intensity ratios of the$$K_{\alpha _1 } /K_{\alpha _2 } $$ and$$L_{\alpha _1 } /L_{\beta _2 } $$ lines have been calculated for206Pb,209Bi and238U with relativistic wavefunctions and retardation effect. Though for a refined calculation, it is necessary to take into consideration several features that are peculiar to mesonic atoms, the present calculations have shown that the observed intensity ratios of mesonic x-rays are not anomalous.

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