Total visitors: 2,086  since 15-3-04

Indian Journal of Pure and Applied Physics

 

 

 

 ISSN: 0019-5596

CODEN: IJOPAU 43 (3) 151-232

Volume 43

Number 3

March 2005

  

 

CONTENTS

 

General

 

Euclidean space dyon solutions

157

Vinod Singh, B V Tripathi & D C Joshi* 

 

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

 

Ultrasonic studies on isomeric butyl alcohol in aqueous solutions

167

V Kannappan & R Jaya Santhi*

 

 
Condensed Matter:Structural,Mechanical and Thermal Properties
 

Crystal and molecular structure of o-thiobenzyl-N,N-dibenzylaniline(C27H25NS)

172

Sanjib Karmakar*, Kabita Patowary, S K Bhattacharjee & A N Talukdar

 

 

Refractive index of ternary liquid systems of squalane (+ hexane + benzene; + cyclohexane + benzene and + hexane  + cyclohexane)

175

G P Dubey*, N Tripathi & S C Bhatia

 

 

Characteristic Bhatia-Thornton  static structure and diffusion coefficients of liquid LiNa and KPb alloys

180

P P Nath & R N Joarder*

 

 

Stability of liquid metal Schottky contacts

184

B P Modi, Achamma John Mathai, K D Patel, V M Pathak & R Srivastava*

 

 

Role of hydrogen and oxygen on the band gap of silicon quantum dots

188

S K Ghoshal*, Umesh Gupta & Karan Singh Gill

 

 

Catalyzed crystallization and some physical properties of Li2O-MgO-B2O3: TiO2 glasses

192

R Balaji Rao, G Naga Raju & N Veeraiah*

 

 

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

 

Study of hyperfine fields in Co2ScSn Heusler alloy

203

N Lakshmi*, Anil Pandey & K Venugopalan 

 

 

Electrical transport in solution‑grown thin films of polyvinylidene fluoride

207 

Devendra K Sahu*, P K Khare & R K Srivastava

 

 

 

Interdisciplinary Physics and Related Areas of Science and Technology
 

Theory and performance of an electrically controlled microwave phase shifter

215

S Sarkar and T Banerjee, D Mondal & B C Sarkar

Low-noise, high resolution microwave synthesis for atomic frequency standards

221

A Sen Gupta1 & D A Howe2

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, March 2005, pp. 157-166

 

Euclidean space dyon solutions

Vinod Singh, B V Tripathi & D C Joshi

 

Using a Cabbibo-Ferrari type non-Abelian field tensor, dyon solutions have been obtained in temporal gauge. Defining the Euclidean fields and imposing the conditions of self and anti-self duality, the obtained solutions have been shown to be the Euclidean space dyon solutions.

 

Keywords: Euclidean space, Dyon solutions, Abelian field tensor, Gauge field theory

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, March 2005, pp. 167-171

 

Ultrasonic studies of isomeric butyl alcohol in aqueous solutions

V Kannappan# & R Jaya Santhi*

 

Ultrasonic velocity (U), density (ρ) and viscosity (η) have been measured of solutions of all the four isomeric butyl alcohol in water at different mole fractions. Acoustical parameters such as adiabatic compressibility (β), Rao constant(R), absorption coefficient (α/f2), internal pressure (πi), cohesive energy (CE), free volume (Vf), intermolecular free length (Lf) and molecular interaction parameter with respect to velocity (χU) were calculated from the experimental data. The intermolecular attraction between the components depends on the mutual association of similar molecules and their dissociation due to attraction between dissimilar molecules. The strength of the bond depends on the length of the alkyl chain and the branching in the alkyl group. The investigations also indicate that there are strong intermolecular hydrogen bonds between alcohol and water molecules.

 

Keywords: Molecular interactions, Ultrasonic studies, Hydrogen bond, Butyl alcohols

IPC Code: B01J19/10

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, March 2005, pp. 172-174

  

Crystal and molecular structure of o-thiobenzyl-N,N-dibenzylaniline (C27H25NS)

Sanjib Karmakara , Kabita Patowaryb, S K Bhattacharjeeb & A N Talukdarc

 

In crystals of o-thiobenzyl N,N-dibenzylaniline (I) (C27H25NS), there are three benzyl groups. N atom is two covalent with the C atoms of the two benzyl groups and the S atom is covalent with the C atom of the other benzyl group. The distances N1-C21, N1-C14 and S1-C7 have been found to be 1.489(4), 1.488(9) and 1.832(8)Ă…, respectively. The molecule is as a whole non-planar. The S1 and the N1 atoms make intramolecular hydrogen bonding. No intermolecular hydrogen bonding has been found and the molecules are stabilised by the network of Van der Waals interaction in their crystalline assembly.

 

[Keywords: C27H25NS, Van der Walls interactions, Crystal structure of C27H25NS, Molecular structure of C27H25NS]

IPC Code: C30B

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, March 2005, pp. 175-179

 

Refractive index of ternary liquid systems of squalane (+ hexane + benzene; + cyclohexane + benzene and + hexane + cyclohexane)

G P Dubey, N Tripathi & S C Bhatia

 

Refractive indices, nD at 298.15, 303.15, 308.15 and 313.15K and densities at 298.15 K have been measured for the ternary mixtures of squalane with hexane + benzene; cyclohexane + benzene, and hexane + cyclohexane over the complete mole fraction range. The validity of the refractive index mixing rules of Lorentz-Lorenz, Gladstone-Dale, Arago-Biot, Wiener and Heller has been tested for the three ternary liquid systems. Relative merits of these mixing rules have been presented and results are analysed in terms of average percentage deviations (APD).

 

[Keywords: Refractive index, Ternary liquid system, Squalane]

IPC Code:  G01N21/57

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, March 2005, pp. 180-183

 

Characteristic Bhatia-Thornton static structure and diffusion coefficients of liquid LiNa and KPb alloys

P P Nath & R N Joarder

 

The liquid alloys, LiNa and KPb are strongly phase separating (ps) and compound forming (cf) alloys respectively and are known to have opposite ordering properties. The Bhatia-Thornton (BT) static structure factors are important indicators of the ordering properties and can best be understood in terms of ordering potential obtained from neutral pseudo atom method. In this paper, it is investigated how this difference in static structural behaviour could influence the dynamical property like self and mutual diffusion coefficients as a function of concentration of the lighter component. The method of Helfand’s linear trajectory principle has been used in the calculation and this gives results comparable with recent calculations based on VACF total memory function formalism. Both the methods yield D versus 1/T curve almost linear similar to what is found for pure liquid metals.

 

[Keywords: Bhatia-Thornton static structure, Diffusion coefficients, Liquid alloy, Liquid LiNa alloy, Liquid KPb alloy]

IPC Code: G01N

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, March 2005, pp. 184-187

 

Stability of liquid metal Schottky contacts

B P Modi, Achamma John Mathai, K D Patel, V M Pathak & R Srivastava

 

All evolutionary aspects of Schottky barriers e.g. the factors contributing to the band alignment at metal-semiconductor interfaces, are still not well understood. Liquid metal-semiconductor interfaces provide an opportunity to probe them since their formation process eliminates or minimizes many influencing factors e.g. formation of oxide layer, changes in surface morphology due to impact of deposited metal atoms etc. when compared to the formation of solid metal semiconductor interfaces. However, the liquid state of metal possessing higher equilibrium thermodynamic energy, may induce instability at interfaces by inducing interfacial reactions ultimately showing up in ageing effect. The liquid metals namely Hg and Ga on p-type silicon show no such effect and hence can be fruitfully exploited for probing evolutionary aspects of metal-semiconductor interfaces through liquid metal route.

 

[Keywords: Schottky barrier, Saturation current, Barrier height, Ideality factor]

IPC Code: B28D5/00

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, March 2005, pp. 188-191

 

Role of hydrogen and oxygen on the band gap of silicon quantum dots

S K Ghoshal, Umesh Gupta & Karan Singh Gill

 

A computer simulation using empirical pseudo-potential Hamiltonian has been performed to examine the variation of the band gap as a function of size and shape of small silicon (Si) quantum dots. It has been found that the gap decreases with increasing dot size. Furthermore, the band gap increases as much as 0.13 eV and 0.35 eV on passivating the surface of the dot with hydrogen and oxygen, respectively. So both quantum confinement and surface passivation determine the optical and electronic properties of Si quantum dots. Visible luminescence is probably due to radiative recombination of electrons and holes in the quantum confined nanostructures. The entire energy spectrum starting from the very low lying ground state to the very high lying excited states for silicon dots having 5, 8, 17 and 18 atoms has been investigated. The role of surface states on the gap energy as well as on the HOMO-LUMO states has also been examined. The results for the size dependence of the HOMO-LUMO gap and the wave functions for the bonding-anti-bonding states have been presented. The role of hydrogen and oxygen passivation on the confinement is also discussed.

 

[Keywords: Quantum dots, Nanostructure, Confinement, Radiative recombination, Passivation photoluminescence, Pseudo-potential and HOMO-LUMO states]

IPC Code: H01L29/76

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, March 2005, pp. 192-202

  

Catalyzed crystallization and some physical properties of Li2O-MgO-B2O3:TiO2 glasses

R Balaji Rao, G Naga Raju & N Veeraiah

 

Li2O-MgO-B2O3:TiO2 glasses were crystallized at three different temperatures. The samples were characterized by scanning electron microscopy and differential scanning calorimetry. Various physical properties viz., optical (optical absorption, IR spectra and thermoluminescence), magnetic (magnetic susceptibility and ESR spectra) have been studied as a function of temperature of crystallization. The investigation is further extended to the dielectric properties viz., dielectric constant, loss and a.c. conductivity over a moderately wide range of frequency and temperature. The analysis of these results indicated a considerable increase in the electrical insulating strength of the samples due to crystallization.

 

[Keywords: Glasses, Crystallization, Optical absorption, IR spectra, Thermoluminescence]

IPC Code: B01D9/00, F21K2/04

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 43, March 2005, pp. 203-206

  

Study of hyperfine fields in Co2ScSn Heusler alloy

N Lakshmi*, Anil Pandey & K Venugopalan

 

Heusler alloy Co2ScSn has been prepared and studied. X-ray diffraction studies showed the structure to be L21 type. Using Sn-119, MĂssbauer studies were carried out to investigate the magnetic hyperfine fields present at the Sn site in this alloy.Applicability of the Blandin and Campbell model for this alloy is tested by calculating the hyperfine fields at Sn site. The results of these calculations are compared with the experimental results.

 

Keywords: Hyperfine field distribution; Heusler alloys; Sn-119 MĂssbauer spectroscopy

IPC code: G01J3/28

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, March 2005, pp. 207-214

 

Electrical transport in solution-grown thin films of polyvinylidene fluoride

Devendra K Sahu*, P K Khare1 & R K Srivastava2

 

The mechanism of electrical conduction in polyvinylidene fluoride (PVDF) films sandwiched between similar and dissimilar electrodes has been investigated in both transient and steady state conduction modes. The thin films are of 20mm thick and obtained by the isothermal immersion technique. The conduction process is examined in a temperature range 40-80°C, with applied dc electric fields ranging from 10 to 100 kV/cm using both types of similar and dissimilar electrodes systems. The nature of transient currents has mainly been attributed to the dipolar nature in the lower temperature region where slope value m is found to vary from 0.43 to 0.62 for similar electrode system and from 0.78 to 0.98 for dissimilar electrode combinations. The steady state conduction current has been found to be strongly temperature dependent. The current-voltage characteristics show two regions of conduction: ohmic conduction with a slope of curve 0.48 to 0.68 at lower and non‑ohmic conduction with a slope 1.87 to 2.05 at higher fields. These results have been interpreted in the light of Richardson-Schottky alongwith space charge limited (SCL) conduction transport mechanism.

 

[Keywords: Transient currents, Steady state conduction, Polyvinylidene isothermal immersion technique, Dipolar orientation, Space charge]

IPC Code: H01C17/065

 

 

 

Indian Journal of Pure & Applied Physics

 Vol. 43, March 2005, pp. 215-220

 

Theory and performance of an electrically controlled microwave phase shifter

S Sarkar and T Banerjee, D Mondal & B C Sarkar

 

A microwave phase shifter (MPS) using a dc bias-controlled injection synchronized Gunn oscillator (ISGO) has been proposed. A continuous phase variation of a microwave frequency signal over a range of -p/2 to p/2 can be made by varying the dc bias of the oscillator. Analytically predicted results, verified with the experimental ones obtained in a novel phase-shift measuring set-up, have been described.

 

[Keywords: Microwave phase shifter, Gunn oscillator, Phase variation, Microwave frequency signal]

IPC Code: G01R29/08

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, March 2005, pp 221-227

 

Low-noise, high resolution microwave synthesis for atomic frequency standards

A Sen Gupta1 & D A Howe2

 

The performance of newer generations of ultra high stability atomic frequency standards based on laser cooled atoms and ions appears to be limited by the local oscillator and the microwave synthesis chain. To improve this performance, the design considerations of microwave synthesizers for Cs hyperfine clock transition at 9.192 GHz that emphasize high resolution, low phase modulation (PM) and amplitude modulation (AM) noise, low spurs near the carrier, and very high phase stability with respect to environmental effects have been studied. Typical performance achieved are: internal fractional frequency stability of 1.5 Ă— 10-15 at 10 s and 1 Ă— 10-18 at 1 day; fractional frequency step of 2 Ă— 10-17 and temperature coefficient less than 0.1-0.5 ps/K. Our design is quite general and enables generation of microwave outputs corresponding to several different atomic transitions. The phase locking of the synthesizer to a high stability external frequency reference based on a cavity stabilized oscillator has been studied.

 

[Keywords: Atomic frequency standards, Microwave synthesis, Synthesizer, Cavity stabilized oscillator]

IPC Code: G 01 R 23/00, G 04 F 10/00