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.

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.

A method using successive approximation is developed for determining the rotational temperatures, when the rotational lines are overlapped. The method is applied to CH (B²Σ⁻ −X² II) band as a test.

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.

The Raman spectra of mixed crystals of [(NH₄)_1−x K_x]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 A_g(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 K_x]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.

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 gradientsu_ij 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 speciesB_1g andB_2g also contain only one line each, the ratio (P₁₁ −P₁₂)/P₆₆ can also be directly obtained from the intensities.

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 bed_xy in our coordinate system with slight admixture of the excited states$$d_{x^2 - y^2 } $$,d_xz andd_yz. 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.

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.

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.