• Volume 52, Issue 4

      April 1999,   pages  351-451

    • Origin of mutual exclusiveness in Bohr’s complementarity principle

      D Sen A N Basu S Sengupta

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      According to Bohr’s complementarity principle, two distinct types of complementarity exist-one of complementary variables and other in the so-called wave-particle complementarity experiments. Some authors have claimed that mutual exclusiveness (ME) in both the cases arise due to uncertainty principle and have analysed the second type in terms of Fourier space analysis and consequent putative “momentum kick” distribution. Some others, on the other hand, have identified the collapse hypothesis as the actual quantum mechanical principle responsible for ME in the interferometry experiments. In this paper the momentum space analysis is thoroughly examined vis-a-vis the general quantum mechanical description in terms of the changes in the wave function. It is argued that such alternative explanations are not in full conformity with the strict quantum mechanical description.

    • On spacetimes dual to spherically symmetric solutions

      Naresh Dadhich L K Patel

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      By defining a duality transformation which implies interchange of active and passive electric parts of gravitational field, it is possible to construct spacetimes dual to solutions of the Einstein equation. Under the duality transformation a fluid spacetime maps into a fluid spacetime with density and pressure transforming as ρ→ (ρ + 3p)/2 andp → (ρ -p)/2. On the other hand a vacuum solution will acquire a global monopole charge. The remarkable feature of spherically symmetric solutions is that it is possible to give a general prescription for writing dual solutions. We demonstrate its application by writing dual solutions to the McVittie solution for a Schwarzschild particle in an expanding universe and to Vaidya’s radiating star solution.

    • Rotating type II null fluids

      P C Vaidya L K Patel

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      A method of obtaining solutions of Einstein field equations, representing rotating type II null fluids is presented. One explicit solution is given and its details are discussed. The well-known deSitter metric is derived as a particular case.

    • Suppression of Smale horseshoe structure via secondary perturbations in pendulum systems

      K I Thomas G Ambika

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      We analyse the use of parametric and quasiperiodic modulations in suppressing horseshoe structure in the phase plane of perturbed pendulum systems. Taking the Froude pendulum as a typical system, four different modulation mechanisms are studied by deriving analytic expressions for the window of the strength of modulation giving suppression in each case. A comparison of the four cases from the point of view of flexibility and efficiency is also given.

    • Beauty-conserving strangeness-changing rare semileptonic decays ofBs meson

      Harpreet Kaur

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      The beauty-conserving strangeness-changing decays ofBs meson are examined. In the charm sector, charm-conserving strangeness changing (Δc = 0, Δs ≠ 0) decays are Cabibbo suppressed and are governed by the CKM elementVus which is much smaller than the CKM diagonal elementVcs, so may be of little interest. On the other hand, in theb-sector, beauty-conserving strangeness changing (Δb = 0, Δs ≠ 0) decays are CKM allowed as the CKM matrix elementVus governing such decays is much larger thanVbc orVbu which govern respectively thebc orbu transitions. The phase space available, however, is too small for the decays considered here. The numerical estimates for the decay widths of two such modes ofBs meson are presented.

    • Two body nonleptonic decays of Λb involving proton

      Harpreet Kaur

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      We study some nonleptonic decays of Λb-baryon involving transition of a heavy to light quark, using nonrelativistic quark model for form factors. The decay rates for two such decays are consistent with the data available. Also these decays can give us information on the CKM matrix element ¦VUb¦.

    • Lifetimes of nuclear excited states with neutron gated recoil distance method

      R Palit P K Joshi S Nagaraj H V Panchal H C Jain

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      A motor driven plunger has been constructed for measuring lifetimes of nuclear excited states in pico second region. An array consisting of six neutron detectors was used to clean up γ-spectra obtained with CS-HPGe detectors. Lifetimes of low excited states in neutron deficient nuclei with low production cross-section e.g.81Y,77Kr and78Rb are reported.

    • Wei Hua’s four-parameter potential: Comments and computation of molecular constants αe and εeXe

      Sarvpreet Kaur C G Mahajan

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      The value of adjustable parameterC in the four-parameter potentialU(r) =De [(1 - exp[-b(r -re)])/(1 -C exp[-b(r -re)])]2 has been expressed in terms of molecular parameters and its significance has been brought out. The potential so constructed, withC derived from the molecular parameters, has been applied to ten electronic states in addition to the states studied by Wei Hua. Average mean deviation for these 25 states has been found to be 3.47 as compared to 6.93, 6.95 and 9.72 obtained from Levine, Varshni and Morse potentials, respectively. Also Dunham’s method has been used to express rotation-vibration interaction constant (αe) and anharmonicity constant (ωexe) in terms ofC and other molecular constants. These relations have been employed to determine these quantities for 37 electronic states. For αe, the average mean deviation is 7.2% compared to 19.7% for Lippincott’s potential which is known to be the best to predict these values. Average mean deviation for (ωexe) turns out to be 17.4% which is almost the same as found from Lippincott’s potential function.

    • Single and multiple ionization of N2 molecules by intense light fields of femtosecond duration

      S Banerjee G Ravindra Kumar D Mathur

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      We report studies on the multiple ionization of the N2 molecule using intense, femtosecond laser pulses. We present details of the experimental characterisation of the light pulses and analysis and detection of the ions produced. Precautions to be taken in intense field ionization experiments are discussed. We illustrate the retrieval of information about different aspects of the ionization process (such as, kinetic energies of the fragments produced, dissociation bond lengths and information on the precursors to fragmentation) using coincidence techniques. We report results of the first measurements of the angular distribution of a highly charged fragment, N3+.

    • Investigation of nonlinear absorption and aggregation in aqueous solutions of rhodamine B using thermal lens technique

      C V Bindhu S S Harilal V P N Nampoori C P G Vallabhan

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      Thermal lensing effect was studied in aqueous solutions of rhodamine B using 532 nm, 9 ns pulses from a Nd:YAG laser. A low intensity He-Ne laser beam was used for probing the thermal lens. Results obtained show that it is appropriate to use this technique for studying nonlinear absorption processes like two photon absorption or excited state absorption and for analyzing dimerization equilibria.

    • Observation of relaxation modes in room temperature ferroelectric liquid crystal mixtures

      K K Raina Arvind K Gathania Buta Singh

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      The dielectric measurements in SmC* and SmA phases of a room temperature ferroelectric liquid crystal mixture FLC-6980 in the cells of different thickness in planer alignment have been carried out in the frequency range 100 Hz to 1 MHz. A relaxation mode (called NRM) whose dielectric increment is less than the Goldstone mode has been observed in the SmC* phase. This mode appears due to the surface effect. Goldstone mode and the soft mode was observable in the vicinity of SmC*-SmA transition temperature (TC*A). The dielectric parameters of the Goldstone mode, new mode and the soft mode have been studied as a function of frequency and temperature. The calculated values for fNRM, δεNRM and distribution parameter αNRM are found to be 325 kHz, 6 and 0.156 for 5μm thick planer cell at 37°C. It is seen that in the vicinity of theTC*A, soft mode obeys the Curie-Weiss law given by mean field theory. The results have been compared with materials of large spontaneous polarization.

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