Volume 52, Issue 4
April 1999, pages 351-451
pp 351-358 April 1999
Origin of mutual exclusiveness in Bohr’s complementarity principle
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.
pp 359-367 April 1999
On spacetimes dual to spherically symmetric solutions
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.
pp 369-374 April 1999
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.
pp 375-387 April 1999
Suppression of Smale horseshoe structure via secondary perturbations in pendulum systems
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.
pp 389-393 April 1999
Beauty-conserving strangeness-changing rare semileptonic decays ofB_{s} meson
The beauty-conserving strangeness-changing decays ofB_{s} 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 elementV_{us} which is much smaller than the CKM diagonal elementV_{cs}, 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 elementV_{us} governing such decays is much larger thanV_{bc} orV_{bu} which govern respectively theb →c orb →u 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 ofB_{s} meson are presented.
pp 395-400 April 1999
Two body nonleptonic decays of Λ_{b} involving proton
We study some nonleptonic decays of Λ_{b}-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 ¦V_{Ub}¦.
pp 401-408 April 1999
Lifetimes of nuclear excited states with neutron gated recoil distance method
R Palit P K Joshi S Nagaraj H V Panchal H C Jain
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.^{81}Y,^{77}Kr and^{78}Rb are reported.
pp 409-420 April 1999
The value of adjustable parameterC in the four-parameter potentialU(r) =D_{e} [(1 - exp[-b(r -r_{e})])/(1 -C exp[-b(r -r_{e})])]^{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 (α_{e}) and anharmonicity constant (ω_{e}x_{e}) in terms ofC and other molecular constants. These relations have been employed to determine these quantities for 37 electronic states. For α_{e}, 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 (ω_{e}x_{e}) turns out to be 17.4% which is almost the same as found from Lippincott’s potential function.
pp 421-434 April 1999
Single and multiple ionization of N_{2} molecules by intense light fields of femtosecond duration
S Banerjee G Ravindra Kumar D Mathur
We report studies on the multiple ionization of the N_{2} 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, N^{3+}.
pp 435-442 April 1999
C V Bindhu S S Harilal V P N Nampoori C P G Vallabhan
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.
pp 443-451 April 1999
Observation of relaxation modes in room temperature ferroelectric liquid crystal mixtures
K K Raina Arvind K Gathania Buta Singh
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 (T_{C*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 f_{NRM}, δε^{NRM} and distribution parameter α_{NRM} 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 theT_{C*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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