• Volume 21, Issue 1

      July 1983,   pages  1-88

    • Propagation of the electromagnetic ion-cyclotron wave in a fusion plasma

      Chandu Venugopal

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      The propagation of the electromagnetic ion-cyclotron wave in a fusion plasma described by a loss-cone structure is discussed. The wavelength is assumed to be much larger than the ion Larmour radius and the ion plasma frequency ≫ the ion-cyclotron frequency. The two modes that propagate in the plasma interact strongly and fuse together under certain conditions making the plasma unstable. The coalescence of the modes is found to decrease with an increase in electron temperature.

    • Spin structure of nucleon

      R Ramachandran

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      The quark spin content of the nucleons is subjected to constraints implied by sum rules due to global approximate chiral symmetries and perturbativeqcd effects. The model, so obtained, has a large polarisation residing in the flavour singlet constituents of hadron. Predictions for the expected longitudinal and transverse spin asymmetries in deep inelastic lepton-nucleon scattering are made on the basis of the standard form of the electromagnetic and charged weak currents.

    • Successive approximation to determine rotational temperature

      M I Savadatti N N Math

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      A method using successive approximation is developed for determining the rotational temperatures, when the rotational lines are overlapped. The method is applied to CH (B2ΣX2 II) band as a test.

    • Effect of collision-induced phase-shifts on the line widths and line shifts of CO2-Ar system

      M L Kurtadikar S C Mehrotra

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      The theoretical calculation of line widths and line shifts for CO2-Ar system is computed by the Mehrotra-Boggs theory. It is shown for this system that the phase shift effect is very important at large values of |m| wherem is the value of rotational quantum numberJ in the lower vibrational state. It is also pointed out that the Salesky-Korff theory is the same as the Mehrotra-Boggs theory.

    • Laser Raman spectra of mixed crystals of [(NH4)1−x Kx]2 SO4

      V Srinivasan C K Subramanian P S Narayanan

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      The Raman spectra of mixed crystals of [(NH4)1−x Kx]2 SO4 in the region 50–3400 cm−1 at 293 K and below 223 K have been reported. At room temperature 293 K, as the concentration of K+ ion increases in the crystal up to 50%, the frequencies of the totally symmetric vibrations of SO42− and NH4+ ions increase and thereafter the frequency of SO42− vibration decreases and attains the value in K2SO4. This change in frequency up to 50% of potassium concentration is due to the breaking of hydrogen bonds of the type N-H...O. The behaviour of Raman intensities of Ag(v1) mode of SO42− for various concentrations (x=0, 0·03, 0·11, 0·5, 0·85) suggest that the phase transition changes from first order type to one of second order. The phase transition in mixed crystals of [(NH4)1−x Kx]2 SO4 can be a cooperative phenomenon arising from a coupling between (NH4)+ ions through hydrogen bonds with the distorted SO42− ions in the low temperature phase.

    • Evaluation of photoelastic constants from first-order Raman intensities of MgF2

      G Swarna Kumari N Satyavathi N Rajeswara Rao

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      A formalism to connect first-order Raman intensities of MgF2 and its photoelastic constants is developed by developing a method of writing internal coordinates in terms of displacement gradientsuij which are not symmetric. It is found that for crystals containing only one line inA1 species, the ratiosP13/P33 and (P11 +P12)/P31 can be directly evaluated from the intensities, without having to derive the intensity formulae; while (P11 +P12)/P13 is independent of the intensities as well as the refractive index of the crystal. It is a function of only the dimensional parameters. In this crystal, since the speciesB1g andB2g also contain only one line each, the ratio (P11P12)/P66 can also be directly obtained from the intensities.

    • Hyperfine interaction parameters and ground-state wavefunctions of vanadyl ion complexes

      V P Seth S K Yadav V K Jain

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      Using crystal field approach a theoretical estimate of the ground-state wavefunctions of vanadyl ion doped in various crystals have been made using ESR data and is found to bedxy in our coordinate system with slight admixture of the excited states$$d_{x^2 - y^2 } $$,dxz anddyz. The hyperfine interaction parameterP and Fermi contact coupling parameterK have also been estimated for these vanadyl-doped crystals. Results agree with similar studies made earlier.

    • Electrical resistance and dielectric constant anomaly in the critical liquid mixture methanol + cyclohexane

      C Shetty M K Gunasekaran V Vani E S R Gopal

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      The electrical resistanceR and the dieletric constant э of the critical binary liquid mixture methanol plus cyclohexane has been measured near the critical point at five different spot frequencies from 10–100 kHz. The data are analysed using a nonlinear least squares routine. The fit is equally good for ana (=0·1) divergence or a 1 −v (=0·35) divergence of dR/dT and dэ/dT. Additional reasons are advanced to indicate that thea divergence is a better description.

    • Two-photon excitation spectrum of benzonitrile vapour

      N Periasamy S Doraiswamy

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      The two-photon excitation spectrum of benzonitrile in the gas phase at about 1 torr has been recorded and analysed in the total energy region of 36300 to 40500 cm−1 using both linearly and circularly polarised light from a Nd-YAG pumped dye laser. The two-photon spectrum consists of strong Franck Condon (fc) transitions bearing a good resemblance to the one-photon spectrum and also vibronic coupling (vc) transitions essentially arising out of the analogue of the benzeneν14. By a comparative study of thetp spectra of various other monosubstituted benzenes, it has been inferred that the strongtp spectrum of benzonitrile should be ascribed to a considerableπ charge delocalization over the phenyl and nitrile groups.

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