Indian Journal of Pure and Applied Physics

Indian Journal of Pure and Applied Physics

VOLUME 39 NUMBER 8 AUGUST 2001

CONTENTS

The Physics of Elementary Particles and Fields

Nuclear Physics

Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics and Fluid Dynamics

Condensed Matter: Structure, Mechanical and Thermal Properties

Indian Journal of Pure & Applied Physics

Vol. 39, August 2001, pp. 481-486

Bounds on the lightest Higg’s boson mass in the minimal supersymmetric standard model

B. Ghosh & S. Chakrabarty

Department of Physics, Visva-Bharati, Santiniketan 731 235

Received 6 December 2000; accepted 14 May 2001

The implications of the lower bound on the standard-model like Higgs boson mass of the order of that reported by LEP 2 collaborations for the parameters of the Minimal Supersymmetric extension of the Standard Model (MSSM) have been studied. The lower bound on tan , on the basis of this presently allowed value of Higgs boson mass has been obtained. The possibility of higher value of lower bound allowed in MSSM and their implications for lower bounds on tan is discussed.

Indian Journal of Pure & Applied Physics

Vol. 39, August 2001, pp.487-490

Excitation functions of (n,p) and (n,) reactions on the isotopes of vanadium and cobalt in the neutron energy range of 13.57-14.71 MeV

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

Institute of Nuclear Science and Technology, AERE, Savar, G.P.O. Box-3787, Dhaka, Bangladesh

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

+ Department of Physics, Jahangirnagar University, Savar, Dhaka, Bangladesh

Received 27 December 2000; accepted 31 May 2001

The excitation functions of the reactions 51V(n,)48Sc, 59Co(n,)56Mn and 59Co(n,p)59Fe have been measured by activation technique using high resolution HPGetector -ray spectroscopy. Monoenergetic neutrons were produced via D-T reaction at J-25 neutron generator facility of the Institute of Nuclear Science and Technology, AERE, Savar, Dhaka, Bangladesh. Monitor Reaction 27Al(n, )24 Na was used to determine neutron flux at different energy position in the range 13.57-14.71 MeV. The measured cross section values along with the literature data have been plotted as a function of neutron energy to get the excitation functions of the reactions. Model calculations using statistical code SINCROS-II was performed to validate the experimental data theoretically.

Indian Journal of Pure & Applied Physics

Vol. 39, August 2001, pp. 491-495

Radium concentration and radon exhalation measurements

in the water around thermal power plants of north India

R P Chauhana, K Kantb, K Maheshc & S K Chakarvartid

aDepartment of Physics, I G N College, Ladwa, Kurukshetra 136 132

bDepartment of Physics, G G D S D College, Palwal, Faridabad 121 102

cD/43, University Campus, Kurukshetra 136 119

dDepartment of Applied Physics, Regional Engineering College, Kurukshetra 136 119

Received 18 January 2001; revised 18 May 2001

Samples of water from different thermal power plants in northern India have been collected and analysed for radium and radon concentration. For the measurements, -sensitive LR-115 type II plastic track detectors are used. The radium and radon levels measured in some samples are high and thus unsafe from health point of view. Based upon the available data, the radon exhalation rates have been calculated. The radium concentration varies from 1.11 to 3.11 Bq l-1 and the radon concentration varies from 10.64 to 29.78 pCi l-1. The radon mass exhalation rates vary from 8.95 to 25.08 mBq kg-1 hr-1 and surface exhalation rates vary from 245.21 to 690.24 mBq m-2 hr-1 in different water samples.

Indian Journal of Pure & Applied Physics

Vol. 39, August 2001, pp. 496-509

MHD effects on heat and mass transfer in flow of a dusty viscous fluid with volume fraction

N P Singh* & Atul Kumar Singh

Department of Mathematics, C L Jain (PG) College, Firozabad 283 205

*Department of Mathematics, VSSD College, Kanpur 208 002

Received 20 April 2000; revised 20 August 2000; accepted 25 January 2001

The laminar flow of an electrically conducting, incompressible, viscous fluid embedded with solid, identical, spherical non-conducting dust particles through a channel consisting of two parallel infinite plates under the influence of a uniform transverse magnetic field has been studied. The solutions for velocity field, temperature distribution and concentration field have been obtained taking into account the volume fraction of dust particles, the expressions for shear stress, rate of heat and mass transfer are also obtained. The effects of various parameters for externally cooled channel walls (Gr > 0) and externally heated channel walls (Gr < 0) are discussed in detail.

Indian Journal of Pure & Applied Physics

Vol. 39, August 2001, pp. 510-513

Ultrasonic attenuation in semi-metallic GdX single crystals (X=P,As,Sb and Bi) in the temperature range 10 to 300 K

S K Kor, Govind Pandey & Devraj Singh

Department of Physics,University of Allahabad, Allahabad 211 002

Received 21 December 2000; accepted 30 May 2001

Ultrasonic attenuation studies have been made in semi-metallic GdX single crystals (X = P, As, Sb and Bi) in the temperature range 10-300 K. Attenuation due to e-p interaction has been studied from 10 to 80K and due to p-p interaction between 100-300 K. Morse potential has been used to evaluate second and third order elastic constants at 0 K and then at higher temperatures. Mason’s approach has been used to evaluate ultrasonic attenuation. Results have been discussed, at Neel-temperature slight kink in ultrasonic attenuation is observed in all the cases.

Indian Journal of Pure & Applied Physics

Vol. 39, August 2001, pp. 514-524

Chemical resistance of some irradiated ceramic-glazes

F M Ezz-Eldin

National Centre for Radiation Research and Technology, Nasr-City, Cairo, Egypt

and

W M Nageeb

National Research Centre, Dokki, Cairo, Egypt

Received 1 November 2000; accepted 10 April 2001

The effect of neutrons irradiation on the chemical durability of some ceramic-glazes with different compositions has been investigated with particular attention to the change in the corrosion rate. Different factors have been studied such as glaze composition, irradiation dose, concentration of the leaching solution, immersion time and temperature of leaching solution. It was found that zircon improved the chemical durability. Corrosion rate increased with increasing concentration of immersion solution up to 2N HNO3 then decreased, also it increased with increasing immersion time and raising the temperature of leaching solution. The amount of the silica released in solution showed a maximum weight loss percent up to 2N HNO3, and then decreased dramatically with increasing the concentration of the tested solution. The corrosion results have been explained in relation to the hydration, diffusion and selective dissolution. The density increases with successive increase of zirconium oxide content reaching the highest value of 2.59 g/cm3. The induced defects obtained on irradiating a glaze, either in the surface or in the bulk, have been assumed to result from neutron irradiation which decreases both the chemical durability and the density.

Indian Journal of Pure & Applied Physics

Vol. 39, August 2001, pp. 525-531

Quantum mechanical structural studies on 2-butanone in the ground and excited electronic states and electronic spectra of its conformers

Archna Sharma, V P Gupta*, Ajit Virdi & Sheela Thakur

Department of Physics, University of Jammu, Jammu 180 004

Received 18 December 2000; revised 4 April 2001; accepted 27 April 2001

2-Butanone (ethyl methyl ketone) may be considered as a two rotor system in which internal rotation may take place about C-C single bond connecting the ethyl and O=CCH3 moieties and also about C-CCH3 bond leading to hindered rotation of the methyl group. Results of ab initio quantum chemical calculations using STO-3G,4-31G, 6-31G and 6-31G** basis sets and semi-empirical calculations in MNDO approximation using modified AM1 Hamiltonian and CNDO/2 approximations are reported .The calculations were undertaken for understanding the structural and spectroscopic characteristics of the rotational isomers of 2-butanone in the electronic ground (S0) and n-* excited (S1) states and for plotting the potential energy curves for these states. It was found that while in S0 state, the molecule may exist in two stable isomeric forms – trans and gauche, it may exist in only one isomeric form – gauche in the S1 state. Completely optimized geometries of the conformers in the two states are reported. In the ground state the trans conformer is more stable than gauche by an enthalpy difference of about 1.5 kcal/mol. Ab initio calculations predict a shallow potential well for the gauche conformer with rotational barrier height of 1.56 kcal/mol for trans-gauche and 0.025kcal/mol (0.35 kcal/mol in AM1) for the gauche-trans conformers. The S0 state of 2-butanone has about 93% trans-conformer, which wholly changes to gauche in the S1 state. The methyl group shows hindered rotation both in the S0 and S1 states with rotational barriers of 0.97 kcal/mol (trans) and 1.36 kcal/mol (gauche) in the S0 state and 1.30 kcal/mol (gauche) in the S1 states. The ionisation potentials of the trans and gauche conformers in the S0 state are 11.010.06 eV and 11.030.08 eV, respectively, while that of the gauche conformer in S1 state is 8.78 eV. Calculations confirm the assignment of experimental band at 278.0 nm to n-* transition and predict transitions near 155 nm, 142 nm and 131 nm corresponding to -* transition, both for the trans and gauche conformers. The blue shift of n-* transition in polar solvent is explained by less polar character of the molecule in the S1 state than in the S0 state.

Indian Journal of Pure & Applied Physics

Vol. 39, August 2001, pp. 532-540

Dielectric properties of different varieties of

rapeseed-mustard oil at different temperatures

A K Bansal, P J Singh & K S Sharma*

Department of Physics, MSJ College, Bharatpur 321 001

and

Satyanshu Kumar & P R Kumar

National Research Centre on Rapeseed-Mustard, Sewar, Bharatpur 321 001

Received 5 February 2001; revised 16 May 2001; accepted 19 June 2001

Dielectric properties of five rapeseed-mustard oil samples having different percentage of erucic acid have been studied at 100 kHz, 8.93 GHz and optical frequency of sodium light. The dielectric constant at optical frequency () is almost the same for all the five samples, while the dielectric constant at 100 kHz (0), the dielectric constant at 8.93 GHz (') and the loss factor ('') show dependence on erucic acid content, but no systematic variation with change in erucic acid is obtained which may be attributed to the presence of other fatty acids in these samples. Temperature variation of dielectric properties has also been investigated in the range 303 to 333 K.  and  decrease regularly with increase in temperature, while ' and '' do not show a regular variation with temperature, except for Hyola-401, which contains zero level of erucic acid. In other samples ' and '' show a maximum or minimum type of behaviour at about 313 K, which may be attributed to the presence of some type of molecular resonance/antiresonance at this temperature. The molar free energy of activation, (F) and the macroscopic relaxation time (m) have also been worked out whose temperature dependence requires consideration of other fatty acids also.