• Volume 17, Issue 3

      September 1981,   pages  203-295

    • Dead time corrections to photon counting statistics I: Classical theory

      M D Srinivas

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      A complete solution is given to the problem of calculating the dead time corrections to the counting statistics of an arbitrary doubly stochastic Poisson process with a non-negative random intensity function. It is shown that for the particular case of an optical field with constant intensity, the general dead time modified counting formula leads to a corrected version of results earlier derived by Bedard.

    • Dead time corrections to photon counting statistics II: Quantum theory

      M D Srinivas

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      The recent formulation of the quantum theory of photodetection, based on the quantum theory of continuous measurements, is extended to the case of a (nonideal) detector which has non-zero dead time. A general result is proven which expresses the dead time modified counting statistics in terms of the counting statistics of anassociated ideal detector. As an illustration, the dead time corrections to the counting statistics of a single-mode free field are worked out, and these corrections are shown to be identical in form to the dead time corrections for a classical optical field of constant intensity.

    • Scattering on energy-dependent separable potentials

      K Niyogi R N Panigrahi D Roy B Talukdar

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      We derive a coordinate space approach to energy-dependent separable potentials and clearly demonstrate its calculational advantage. The results presented include expressions for (i) low-energy scattering parameters and (ii) off-energy-shellT andK matrices. We study energy dependence of the effective potential with particular emphasis on cross-channel suppression effects.

    • Centrifugal distortion effects in the microwave spectrum of allyl alcohol

      A I Jaman D K Ghosh

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      The ground state rotational spectrum of allyl alcohol has been reinvestigated in the frequency range 12.5–40.0 GHz. A detailed centrifugal distortion analysis has been carried out and theJ-value of the assigned transitions has been extended to 45. The evaluated parametes are presented.

    • The B-A system of CP molecule

      R Tripathi S B Rai K N Upadhya

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      The B-A system of CP molecule has been reinvestigated. The rotational structures in the (0, 0) and (1, 1) bands have been photographed in the second order of a 10.6 m grating with 25µ slit width. The molecular constants have been determined using a weighted least squares fit computer program. It is found that the spin-splitting constant in the B-state is negative and not positive as reported by previous workers. An accurate value ofα in the A-state could be determined. The present analysis also suggests that the spin-splitting constant in the ground state of CP should be positive, hence the assignment of theR1 andR2 orP1 andP2 branches in the B-X system of CP by Barwaldet al should be interchanged.

    • Localized modes of ammonium ion in KCl lattice

      R Kesavamoorthy V Umadevi Debendranath Sahoo

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      Following the standard Green’s functions matrix partitioning technique, the force constant changes needed to explain the translational (6.8 THz) and torsional (10.1 THz) modes occurring in the KCl:NH4+ system are calculated. Three different defect site symmetries are considered for the ammonium ion impurity. These are (i)Oh, in which the ammonium ion is a free rotor, (ii)Td, in which it is a hindered rotor and (iii)C4v, in which it rotates freely about a N - H ... Cl axis and librates around the other two crystallographic axes.Oh defect symmetry explains only the translational mode, while in the other two symmetries both the modes are explained with reasonable changes in the force constants. It is also shown that the same set of force constant changes explains the local modes in the deuterated sample as well.

    • Electrical conductivity studies of cobalt-precipitation in RbCl crystals

      S K Gupta S D Pandey

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      The results of electrical conductivity measurements in heavily doped RbCl:CoCl2 crystals with 2500 and 6000 ppm of cobalt are being reported in this paper. The different regions of the conductivity plots for the crystals with the two concentrations of cobalt have been explained and relevant energy parameters determined. The crystals with 6000 ppm of cobalt have been found to contain two types of precipitates one of these being of the same type as that existing in RbCl crystals with 2500 ppm of cobalt while the other being of a different composition.

      Further, it has been found that the crystals appear blackened after heating during measurements. The blackening has been attributed to the expulsion of cobalt from the bulk of the crystal which forms an oxide at the surface.

    • Enhancement of vacuum transmission of intense electron beam through cusp magnetic field using dielectric drift tubes

      P I John K K Jain

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      A technique for improving the transmission of intense electron beams through cusp magnetic field in vacuum using dielectric drift tubes has been demonstrated. The plasma produced by the material of the dielectric tube increases the transmission efficiency by a factor of four over vacuum values.

    • Confinement of massless particles: Photon

      P K Jena T Pradhan

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      Confinement of massless particles in a suitably chosen dielectric medium is considered. Light waves of selected frequencies are shown to be confined in a medium with dielectric constantε(r)=a/rb2. A wave theoretical analysis gives equispaced frequency spectrum for the confined light, the radial dependence of its electric wave vector resembling that of hydrogen atom wave functions. In the large frequency limit an eikonal approximation of the problem gives elliptic orbits for the confined rays. Higher frequency orbits are shown to be closer to the centre of the medium than the lower frequency ones.

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