Indian Journal of Pure and Applied Physics

 

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VOLUME 40                                                    NUMBER 8                                                        AUGUST  2002

CODEN:IJOPAU 40(8) 529-602(2002)                                                                                                         ISSN: 0019-5596

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CONTENTS

 

Nuclear Physics

Measurement of (n, 2n) reaction cross-sections on isotopes of zinc, germanium and scandium in

      neutron energy range 13.82-14.71 MeV

      M S Uddin*, S K A Latif, M A Halim, M N Islam, R U Miah, N I Molla & M R Zaman

 

533

Azimuthal asymmetry of slow particles in high energy nuclear interaction

      Subir Sarkar & T D Goswami*

539

Condensed Matter: Structure, Mechanical and Thermal Properties

Design of microprocessor controlled RTA system for processing of ion implanted semiconductor

      materials

      M M Belekar, A M Narsale*, K V Sukhatankar, B M Arora & Y P Ali

 

543

Thermodynamics of crystal nucleation in drops, hanging or sitting in an external electric field

      K V Saban & George Varghese*

552

Non-static global monopole in higher dimension

      Farook Rahaman

556

Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties

Diffusion induced parametric amplification in centro-symmetric semiconductor plasmas

      S Ghosh*, Giriraj Sharma & M P Rishi

 

561

Degeneracies of dyonic harmonic oscillator and effect of magnetic field on dyonium

      S C Joshi, V P Pandey* & B S Rajput

569

Importance of coherence length in explaining super-conducting behaviour of cuprate superconductors

      Bhaskar Gahtori, Ratan Lal & S K Joshi*

574

Absorption and emission spectral studies of Sm3+ and Dy3+ doped alkali fluoroborate glasses

      R R Reddy, Y Nazeer Ahammed, P Abdul Azeem, K Rama Gopal, T V R Rao,

      S Buddhudu* & N Sooraj Hussain

577

Relaxation phenomena in methyl benzenes and ketones from ultra high frequency conductivity

      K Dutta, A Karmakar, S K Sit & S Acharyya*

588

News Scan

Trapping of light

      Poonam Bhatt

 

597

____________

*The corresponding author has been indicated by (*) mark in case of papers with more than one author

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 40, August  2002, pp. 533-538

Measurement of (n,2n) reaction cross-sections on isotopes of

zinc, germanium and scandium in neutron energy range

13.82-14.71MeV

M S Uddin, S K A Latif, M A Halim, M N Islam, R U Miah, N I Molla & M R Zaman*

Institute of Nuclear Science and Technology, AERE, GPO Box-3787, Dhaka-1000, Bangladesh

*Department of Applied Chemistry and Chemical Technology, Rajshahi University, Rajshahi-6205, Bangladesh

Received 5 December 2001; accepted 24 August 2002

The cross-sections for the reactions 64Zn(n,2n)63Zn, 76Ge(n,2n)75m+gGe and 45Sc(n,2n)44mSc were measured in the energy range 13.82-14.71 MeV. The activation technique was used in combination with high resolution HPGe detector gamma-ray spectroscopy. Neutrons were produced via D-T reaction at J-25 neutron generator of the Institute of Nuclear Science and Technology, AERE, Dhaka, Bangladesh. The neutron flux at each energy was determined using monitor reaction 27Al(n,a)24Na. The nuclear model calculations using the computer codes SINCROS-II and EXIFON were undertaken to describe the excitation functions of the investigated reactions.

 

Indian Journal of Pure & Applied Physics

Vol. 40, August 2002, pp. 533-542

Azimuthal asymmetry of slow particles in

high energy nuclear interaction

Subir Sarkar & T D Goswami

Department of Physics, Gauhati University, Guwahati  781 014

Received 20 March 2001; accepted 21 May 2002

An asymmetry in the angular distribution of slow particles in the azimuthal plane has been observed during high energy nuclear disintegration of photo emulsion nuclei exposed to 1.8 GeV/c k- and 20 GeV/c protons. The mechanism of disintegration is not in accordance with the cascade-evaporation model, which is based on isotropic emission of slow particles. Deviation from isotropy indicates that some of the slow particles might be emitted well before the thermal equilibrium is reached in the disintegrating system.

 

Indian J Pure & Applied Physics

Vol. 40, August  2002, pp. 543-551

Design of microprocessor controlled RTA system for processing of ion implanted semiconductor materials

M M Belekar1, A M Narsale1, K V Sukhatankar1, B M Arora2 & Y P Ali3

1Department of Physics, University of Mumbai, Vidyanagari, Mumbai 400 098

2Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005

3Department of Physics, Hadhramout University of Science & Technology, Hadhramout, Yemen

Received 26 December 201; revised 8 March 2002; accepted 30 May 2002

Rapid thermal annealing (RTA) is one of the important techniques used for removal of radiation induced defects in ion implanted semiconductor materials. A complete stand-alone microprocessor controlled RTA system has been designed and fabricated. It uses a 12 kW halogen lamp bank for rapid radiative heating of the sample and provides good temperature ramp-up rate of >120 °C/s up to a temperature of 700 °C. A gas line assembly has been provided to carry out the annealing in hydrogen, nitrogen, argon and oxygen gas ambient. The system temperature is programmable in the step of 1 °C each up to the maximum attainable temperature of 1080 °C. The soak time can be programmed from a minimum of 1 s up to a maximum of 15 min per set temperature. The system has been used for annealing of single crystal GaAs substrates implanted with 70 MeV 56Fe ions with a dose of 1 ´ 1014 ions/cm2, in the temperature range 100-600 °C. The implanted samples have been investigated by optical transmission measurements over photon energy range 0.1-1.4 eV, after each annealing stage. The mid-gap defect states are annealed out more rapidly than the near-band edge defect states during annealing up to 350 °C whereas, the near-band edge defect states are annealed out more rapidly than the mid-gap defect states during annealing between 350-600 °C.

 

Indian Journal of Pure & Applied Physics

Vol. 40, August 2002, pp. 552-555

Thermodynamics of crystal nucleation in drops, hanging or

sitting in an external electric field

K V Saban & George Varghese

Crystal Physics Centre, St Berchmans’ College, Changanacherry 686 101

Received 26 December 2001; revised 8 March 2002; accepted 18 August 2002

The influence of an external electric field on the thermodynamics and kinetics of crystal formation in spherical droplets has been studied. A numerical analysis is performed with NaCl-water system and the strength of the electric field, which would produce an appreciable change in the nucleation process, is calculated. The changes in the case of proteins and other macromolecules are discussed.

 

Indian Journal of Pure & Applied Physics

Vol. 40, August 2002, pp. 556-560

Non-static global monopole in higher dimension

Farook Rahaman

Khodar Bazar, Baruipur, 24 Parganas (South) 743 302

Received 5 March 2001, revised 5 January 2002, accepted 18 March 2002

A class of non-static solution around global monopole resulting from the breaking of a global SO(3) symmetry in a five-dimensional space-time is obtained. The energy momentum tensor for the monopole configuration is taken as Ttt = Trr = r (r,t). Trajectory of the test particle has also been studied. This paper extends earlier work of Chakraborty & Biswas, Int J Mod Phys A, 13, (1998) 1228, to its five-dimensional analogue.

 

Indian Journal of Pure & Applied Physics

Vol. 40, August 2002, pp. 561-568

Diffusion induced parametric amplification in centro-symmetric semiconductor plasmas

S Ghosh, Giriraj Sharma* & M P Rishi

School of Studies in Physics, Vikram University, Ujjain (MP) 456 010

Received 14 September 2001; revised 28 March 2002; accepted 10 August 2002

Based on hydrodynamic model of plasmas and using straight forward coupled mode theory an analytical investigation of parametric interaction of high frequency pump with semiconductor plasma and consequent amplification of acoustic wave has been carried out in centro-symmetric semiconductor medium. The phenomenon of parametric amplification is treated as three-wave interaction process, involving second-order non-linearity of the medium. It is found that, diffusion induced non-linear current density is responsible for the generation of second-order optical susceptibility c(2) in a centro-symmetric medium. It has been found that, for crystals with n0 = 1024 m-3, c(2) = 5.01 ´ 10-7 SI and n0 = 1022 m-3, c(2) = 4.13 ´ 10-9 SI, these values are fairly in agreement with the experimentally observed value for III-V compound semiconductors. Steady-state gain constant and threshold pump intensity for the onset of parametric instability, have also been estimated. The analysis has been performed in non-dispersive regime of the acoustic wave, which is one of the preconditions for achieving an appreciable initial steady-state growth of the parametrically generated signal mode. The minimum threshold pump amplitude E0th at wave number k = 7.4´107 m-1 (say km) has been found. This km is greatly influenced by carrier concentration and diffusion coefficient of the carriers in the medium. It is found that, gain increases rapidly with the increase in pump amplitude ( > E0th) and doping concentration of the medium. Hence, the desired value of the gain can be obtained by adjusting pump intensity and doping concentration of the medium concerned.

 

Indian Journal of Pure & Applied Physics

Vol. 40, August 2002, pp. 569-573

Degeneracies of dyonic harmonic oscillator and

effect of magnetic field on dyonium

S C Joshi*, V P Pandey** & B S Rajput***

Department of Physics, Kumaun University, Nainital, Uttaranchal 263 002

[E-mail: *scjku@yahoo.com; **vindhyeshwari@yahoo.com; ***vc@vsnl.com]

Received 21 June 2001; revised 1 March 2002; accepted 15 May 2002

Study of dyonic harmonic oscillator and dyonium has been undertaken by incorporating magnetic coupling parameter for dyons in the generalised expression of the Hamiltonian. It is shown that, degeneracy levels for such a system are modified from the usual degeneracy levels of quantum electrodynamics due to the presence of magnetic charge on dyon. Study of dyonium under the influence of external magnetic field also shows that, energy levels are modified due to the presence of magnetic charge on dyon and degeneracy of energy levels is lifted, causing splitting of energy levels in the usual way. The radiation from the transition between these levels may indicate the existence of monopoles.

 

Indian Journal of Pure & Applied Physics

Vol. 40, August 2002, pp. 574-576

Importance of coherence length in explaining superconducting behaviour of cuprate superconductors

Bhasker Gahtori, Ratan Lal & S K Joshi

Theory Group, National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110 012

Received 27 May 2002; accepted June 2002

It has been argued that, in explaining their data on cuprate superconductors some authors appear to have considered incorrect variation of the coherence length with impurity concentration. Considering two cases from the existing literature, namely the explanation of critical current density of Pr doped YBa2Cu3O7 samples by Hedge et al.1 [Phys Rev B, 48 (1993) 6465], and the explanation of the penetration depth of Fe doped YBa2Cu3O7 samples by Hayani et al.2 [Physica C, 221 (1994) 319], it has been clarified that, these proposed explanations may be misleading.

 

Indian Journal of Pure & Applied Physics

Vol. 40, August 2002, pp. 577-587

Absorption and emission spectral studies of Sm3+ and Dy3+ doped alkali fluoroborate glasses

R R Reddy, Y Nazeer Ahammed, P Abdul Azeem, K Rama Gopal & T V R Rao

Department of Physics, SK University, Anantapur 515 003

and

S Buddhudu & N Sooraj Hussain

Department of Physics, SV University, Tirupati, AP

Received 23 July 2001; revised 22 December 2001; accepted 8 March 2002

Absorption and photoluminescence spectra of Sm3+ and Dy3+ doped alkali fluoroborate glasses of the composition 90.5 B2O3 + 4 AlF + 5 RF + 0.5 LnF3 (R= Li, Na, K and Ln = Sm, Dy) are reported. On excitation, with 402 nm, the Sm3+ glasses were found to be orange fluorescent in colour and richness of that colour was high in the Na+ glass, compared to Li+ and K+ glasses. Similarly, on excitation with 398 nm, the Dy3+ glasses were fluorescent yellow and that colour was richer in the K+ glass.

 

Indian Journal of Pure & Applied Physics

Vol. 40, August 2002, pp. 588-596

Relaxation phenomena in methyl benzenes and ketones from ultra high frequency conductivity

K Dutta, A Karmakar, S K Sit & S Acharyya

Department of Physics, Raiganj College (University College), PO Raiganj, Dist Uttar Dinajpur (WB) 733 134

e-mail: koushikduttajsm@rediffmail.com

Received 30 August 2001; revised 14 February 2002; accepted 30 May 2002

The relaxation time t and dipole moment m of some methyl benzenes and ketones (j) in a non-polar solvent benzene (i) at 25 °C under 9.585 GHz electric field have been obtained from the measured real and imaginary parts eij˘ and eij˛ of hf complex relative permittivity eij* at various weight fractions wj ’s of a polar liquid. The methodology to get t from the ratio of the individual slopes of real sij˘(=we0eij˛) and imaginary sij˛(=we0eij˘) parts of complex hf conductivity sij* curve against wj’s, seems to be a significant improvement over the existing one like the linear slope of sij˛sij˘ curve. The variation of sijwj curve like sij˛wj curve is often convex indicating the probable occurrence of phase change in the polar-nonpolar liquid mixture after a certain concentration. The convex nature of sij˘wj curves for some systems indicate the maximum absorption of hf electric energy unlike other systems. The estimated m’s from slope b of hf conductivity sijwj curve and t from both the methods are compared with the work of Gopalakrishna to establish the applicability of the methods. Theoretical dipole moments mtheo’s from available bond angles and bond moments are calculated by considering inductive, mesomeric and electromeric effects of the substituent polar groups of the molecules.

 

Indian Journal of Pure & Applied Physics

Vol. 40, August 2002, pp. 597-598

News Scan

Trapping of Light

The speed of light is one of the important and wonderful properties of the universe. The light is composed of massless particles called photons which travel at the speed of 300,000 km/ s But, recent experiments have even slowed down the speed of light, stored light, and even brought the speed of light to a complete halt and reversed its direction. These experiments of slowing a beam of light to a halt may pave the way for the development of new optical communication technology, quantum optical data storage, tabletop black holes, quantum computers and quantum internet.