• Volume 20, Issue 2

      February 1983,   pages  105-174

    • Generalized pencils of rays in statistical wave optics

      R Simon

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      The recently introduced generalized pencil of Sudarshan which gives an exact ray picture of wave optics is analysed in some situations of interest to wave optics. A relationship between ray dispersion and statistical inhomogeneity of the field is obtained. A paraxial approximation which preserves the rectilinear propagation character of the generalized pencils is presented. Under this approximation the pencils can be computed directly from the field conditions on a plane, without the necessity to compute the cross-spectral density function in the entire space as an intermediate quantity. The paraxial results are illustrated with examples. The pencils are shown to exhibit an interesting scaling behaviour in the far-zone. This scaling leads to a natural generalization of the Fraunhofer range criterion and of the classical van Cittert-Zernike theorem to planar sources of arbitrary state of coherence. The recently derived results of radiometry with partially coherent sources are shown to be simple consequences of this scaling.

    • Multiple focus formation in a Mather gun device

      Anurag Shyam M Srinivasan

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      Along with the normally produced pulses of dI/dt, x-ray, optical emission, neutrons and ions by a Mather type plasma focus gun, one more set of pulses were observed to be generated by a low energy device at Trombay, a few 100 ns after the first set of pulses, in majority of the discharges. In a small number of discharges even three or more sets of pulses were observed. Signals from pick-up probes placed in the run down region of the device suggest formation of more than one sheath which subsequently may form more than one focus which in turn is responsible for the second and subsequent sets of pulses.

    • On an integral over the surface ofN-dimensional unit sphere

      Nazakat Ullah

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      An integral which occurs in the new matrix ensembles and the width fluctuation factor is evaluated using a transformation which changes a Gaussian into an exponential. It is expressed in the form of a series whose terms are found using a simple recursion relation. It is shown that the series can be summed in closed form for the two-dimensional case.

    • Optical absorption spectrum of Ni2+ ion doped in synthetic lecontite

      S V J Lakshman T V Krishna Rao

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      The optical absorption spectrum of Ni2+ ion doped in lecontite (sodium ammonium sulphate dihydrate) single crystal has been studied at room and liquid air temperatures. All the bands could be assigned assumingOh symmetry for the Ni2+ ion in the crystal. The splitting of3T1g (F) band at liquid air temperature has been attributed to spin-orbit interaction. The crystal field and spin-orbit parameters derived areDq=1000 cm−1;B=740 cm−1;C/B=4.27 and ζ=600 cm−1. All the bands observed show a blue shift when the crystal was cooled to liquid air temperature.

    • Masses and some electromagnetic properties of charm andb-quark hadrons in a bag model with a variable bag pressure

      P K Chatley

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      We investigate how a new bag phenomenology with a variable bag pressure as its main ingredient is successful in reproducing various properties of heavy hadrons. Our results for masses, magnetic moments and M1 radiative decay widths indicate that these properties arise in a natural and consistent manner from the theory and that no additionalad hoc assumption is required to explain them.

    • Theoretical calculation of electron-impact resonance excitation of alkali atoms

      C S Singh R Srivastava D K Rai

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      Total cross-section for electron impact excitation of the resonance levels in Li, Na and K are calculated using the method due to Crothers and McCarroll. The results are compared with other available theoretical and experimental data.

    • Infrared and raman studies of some naphthols

      S Ram V N Pandey S N Thakur

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      Vibrational spectra of α-naphthol,β-naphthol andβ-naphthol-OD have been recorded in the solid and solution phases. A number of bands, common to all the three compounds, have been correlated with earlier naphthalene assignments and an attempt has been made to identify certain frequencies with vibrational modes that are centred in the substituentsOH andOD. TheCs symmetry is assumed for each molecule.

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