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The anisotropy of L x-rays from the decay of L3 subshell vacancies in uranium and thorium following photoionization is investigated by measuring the angular distribution of photon induced L3 x-rays (Ll, L and L) in these elements. To enhance the chance of anisotropic emission of these x-rays, the measurements are made using selective photoionization of the L3 subshell in these elements. In contrast to the findings of earlier experiments in which L was observed to be isotropic, the present experiment gives clear-cut evidence of the anisotropic emission of this group and thus, strengthens the view of Flugge et al (1972 Phys. Rev. Lett. 29 7) that the vacancies after photoionization of states with J > ½ are aligned. The possible reasons explaining the observation of earlier workers that L emission is isotropic are also discussed.

Presents an investigation of the filamentation instability of an upper hybrid laser radiation propagating in a magnetoplasma. The non-uniformity of the pump wave causes the redistribution of the electrons in the plasma. This modified density distribution is responsible for the self-focusing of the main beam. The spatial and temporal growth rates of filamentation instability increase with an increase in the magnetic field. For uniform plane waves, the spatial and temporal growth rates increase with an increase in beam power, but for gaussian beams, the growth rates are an oscillatory/decreasing/increasing function of the distance of propagation inside the plasma.

Presents an investigation of the generation of a plasma wave at pump wave frequency and second harmonic generation caused by a self induced transverse inhomogeneity introduced by a Gaussian electromagnetic beam in a hot collisionless plasma. In the presence of a Gaussian beam the carriers get redistributed from the high field region to the low field region by ponderomotive force and a transverse density gradient is established in the plasma. When the electric vector of the main beam is parallel to this density gradient, a plasma wave at the pump wave frequency is generated. In addition to this the transverse intensity gradient of the electromagnetic wave also contributes significantly to the plasma wave generation. The power of the plasma wave exhibits a maximum and minimum with the power of the pump wave (at z=0). The generated plasma wave interacts with the electromagnetic wave and leads to the generation of a second harmonic.

Presents an investigation of the temporal growth rate of filamentation instability of a uniform laser beam propagating along and perpendicular to the static magnetic field in a strongly ionised plasma. The nonlinearity of the dielectric constant arises on account of diffusion of non-uniformly heated carriers (on account of fluctuations in the intensity of the main beam). Both the mechanism of energy loss of electrons, namely the thermal conduction and collisions with heavy particles have been taken into consideration.

Presents an investigation of the effect of the saturating nonlinearity of the pump wave on the spatial growth of the filamentation instability of a Gaussian plane electromagnetic beam in a collisionless magnetoplasma. The nonlinearity is caused by the redistribution of carriers by the ponderomotive force. The growth rate is not a monotonically increasing function of the beam intensity and the optimum size of perturbation increases with the beam intensity beyond a certain value of the beam intensity which is in contrast to the uniform plane beam case. The growth rate decreases with the distance of propagation due to the self-focusing effects and is enhanced with the increase of static magnetic field for extraordinary waves, but the reverse is true for ordinary waves.