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Indian Journal of Pure and Applied Physics

 

 

 

ISSN: 0019-5596

 

CODEN:IJOPAU 41(9) 671-742(2003)

VOLUME 41

NUMBER 9

SEPTEMBER    2003

 

CONTENTS

The Physics of Elementary Particles

Thermodynamical properties of neutron matter using Gogny effective interaction

Kh A Ramadan* & H M M Mansour

 

675

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

Titania films deposited by thermal evaporation as humidity sensor

B C Yadav & R K Shukla*

 

681

Ultrasonic study of some ophthalmic solutions in aqueous medium

K Ravindra Prasad* & P Subramanyam Naidu

686

Ultrasonic studies on molecular interaction of certain carbonyl compounds in

n-hexane and chloroform solutions

V Kannappan*, S Xavier Jesu Raja & R Jaya Santhi


690

Security holograms readable with an encoded key hologram

Sushil K Kaura*, D P Chhachhia, Amit K Sharma & A K Aggarwal

696

Condensed Matter: Structural, Mechanical and Thermal Properties

Measurement of heat storage coefficient of solid-solid-air mixtures at different pressures

A Kshrotriya* & S K Jain

 

 

 

700

 

Thermal evaporation of diglycine hydrogen fluoride crystals

M M Khandpekar

704

Frequency distribution function of phonons in different layers of graphite

S P Tewari*, Poonam Silotia & Aditya Saxena

707

Measurement of effective thermal conductivity and thermal diffusivity for assessing the integrity of fiber to matrix bond in natural fiber composite

R Mangal, N S Saxena*, G P Joshi, M S Sreekala & S Thomas


712

Temperature dependence of exciton life-time in GaAs/AlGaAs quantum wells

S K Pandey, M Ramrakhiani* & B P Chandra

719

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

Study of dark and photoconductivity of Sb-doped CuInSe2 thin films

Rakesh Kumar, Naresh Padha, P K Shishodia & R M Mehra*

 

723

Charge imbalance in a non-equilibrium superconductor

B A Mattoo

727

Effect of charge transfer behaviour on the dielectric and ac conductivity of Co-Zn ferrite doped with rare earth element

M A Ahmed* & M H Wasfy


731

____________

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

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 675-680

 

Thermodynamical properties of neutron matter
using Gogny effective interaction

Kh A Ramadan & H M M Mansour

 

 

Investigation of the equation of state of hot and cold neutron matter using Gogny D1 effective interaction is presented. The binding energy per particle, spin symmetry energy, free energy, pressure, entropy, sound velocity and magnetic susceptibility are calculated as a function of density r fm-3. The calculations cover a wide range of densities and are discussed in comparison with the realistic interaction calculation of Friedman and Pandharipande [Nucl Phys A, 361 (1981) 502].

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 681-685

 

Titania films deposited by thermal evaporation as
humidity sensor

B C Yadav & R K Shukla

 

 

The humidity sensors based on optical methods are best suited for those situations where remote analysis capability, high sensitivity and compactness of the device are the criteria for the measurement of humidity levels. The sensing element of optical humidity sensors consists of a rutile structured TiO2 thin film deposited on the base of an isosceles glass prism. Such a TiO2 film is porous and highly sensitive to humidity. Light from He-Ne laser source enters the prism from one of the isosceles faces of the prism, and then gets reflected from the glass film interface, before emerging out from the other isosceles face of the prism. The emergent beam is collected through an optical fiber, which is connected to an optical power meter for measurement. Variations in the intensity of light caused by changes in humidity lying in the range 5-95% have been recorded.

 

 

 

Indian J Pure & Applied Physics

Vol. 41, September 2003, pp. 686-689

 

Ultrasonic study of some ophthalmic solutions in
aqueous medium

K Ravindra Prasad & P Subramanyam Naidu

 

 

Seven ophthalmic systems belonging to one class, which reduce the intra-ocular pressure have been chosen for an ultrasonic study. These solutions have pilocarpine nitrate/pilocarpine hydrochloride/timolol maleate as major components. Ultrasonic velocity and density have been measured in the aqueous solutions of these ophthalmic systems at 308.15 K. The deviations in velocity and compressibility have been computed. The effect of these systems on the structure of water has also been analyzed, employing Jacobson’s theory of adiabatic compressibilities.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 690-695

 

 

Ultrasonic studies on molecular interaction of certain carbonyl compounds in n-hexane and chloroform solutions

V Kannappan, S Xavier Jesu Raja, & R Jaya Santhi

 

 

The ultrasonic velocities (U), densities (r), and viscosities (h) are measured in n-hexane and chloroform solutions of acetophenone, ethyl methyl ketone and benzaldehyde at 298 K, in the concentration range 0.05-1 M. The variation in ultrasonic velocity values indicate solute-solvent interactions in both the media and stronger interactions are observed in chloroform solutions. Acoustical parameters such as adiabatic compressibility (b), linear free length (Lf), relaxation time (t), absorption coefficient (a/f2), molecular interaction parameter (c), and solvation number (Sn) values are also calculated. These values indicate that, the carbonyl compounds are strongly attracted by chloroform molecules probably through inter molecular hydrogen bond.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 696-699

 

 

Security holograms readable with an encoded key hologram

Sushil K Kaura, D P Chhachhia, Amit K Sharma & A K Aggarwal

 

 

 

A simple and cost effective two-step method for making security holograms, which are readable with an encoded key hologram, has been presented. These security holograms contain an additional security feature which can be read only by using an encoded key hologram in the reading process. In the final reading process, the sharp focus spot emerges only when the security hologram is illuminated by the decoding, reconstructing beam generated from the encoded key hologram. Since the verification/identification pattern in these holograms is a sharp focus spot rather than an image pattern, this type of security holograms are suitable for both visual as well as machine inspection. They can also be used as security codes for better protection against counterfeiting in the embossed holograms. Experimental results achieved have been discussed.

 

 

  

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 700-703

 

 

Measurement of heat storage coefficient of
solid-solid-air mixtures at different pressures

A Kshrotriya & S K Jain

 

 

Using a plane heat source technique, the heat storage coefficient (HSC) of some varieties of selected three phase systems (solid-solid-air mixture) like, loose cement dispersed with marble powder, aluminium powder and iron powder respectively, has been measured at varying interstitial air pressures. The behaviour of the HSC values with the variation of pressure between the range 0.1 to 760 mm of mercury has been discussed. There is a marked change in the values of HSC for increase or decrease in the pressure region from 0.1 to 760 mm of mercury.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 704-706

 

 

Thermal evaporation of diglycine hydrogen fluoride crystals

M M Khandpekar

 

 

Diglycine hydrogen fluoride crystals have been grown from aqueous solution by slow evaporation technique, at room temperature. Thermal evaporation at the surface of the crystal shows formation of boat-shaped pits, in accordance with the (100) symmetry of cleavage face, with density of pits concentrated in some regions. The sizes of the pits increase at the same sites on prolonged thermal etching and show correspondence of few pits on matched counterparts. The rare evidence of mismatch of new domains is detected. The presence of typical circular feature, pits formed on domains, thick and thin domain lines and the glide band due to thermal stresses are illustrated.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 707-711

 

 

Frequency distribution function of phonons in
different layers of graphite

S P Tewari, Poonam Silotia & Aditya Saxena

 

 

Variation in the phonon frequency distribution function has been computed, using recently suggested unfolding technique by the authors, from the temperature-dependent mean square displacement of a carbon atom on a graphite surface, when different number of graphite layers are added on either side of it, ranging from 3 to 13 and then to a very large number. The cross-over of the dynamics from nearly two-dimensional to quasi two-dimensional situation is thus studied.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 712-718

 

 

Measurement of effective thermal conductivity and
thermal diffusivity for assessing the integrity of
fiber to matrix bond in natural fiber composite

R Mangal, N S Saxena, G P Joshi, M S Sreekala & S Thomas

 

 

 

Thermal conductivity and thermal diffusivity of pineapple leaf reinforced phenol formaldehyde composite have been studied with special reference to chemically treated fibers using the transient plane source (TPS) technique, at room temperature and normal pressure. All the composites were made of 40% fiber by weight. The fibers were treated with alkali, silane and toluene diisocyanate. It was found that, thermal conductivity and thermal diffusivity of the composites increase after chemical treatment. The thermal conductivity of alkali treated fiber was found to be maximum in the present study. The thermal conductivity of treated and untreated fibers was calculated theoretically by Bruggman's model. The results of model calculation showed an increase of thermal conductivity of treated fiber over the thermal conductivity of untreated fiber.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 719-722

 

 

Temperature dependence of exciton life-time in
GaAs/AlGaAs quantum wells

S K Pandey, M Ramrakhiani & B P Chandra

 

 

 

In GaAs/AlGaAs quantum well structures, the confinement of electrons as well as, holes in GaAs well region causes enhancement of Coulomb interaction, which leads to formation of excitons with large binding energy, and, therefore, excitonic states persist even up to room temperature. The phenomenon of photoluminescence (PL) in such structures is dominated by radiative recombination of excitons. The PL and PL decay time is found to depend on temperature. At higher temperatures, thermal population of higher excitonic sub-bands and exciton ionization also need to be considered. The temperature dependence of radiative and non-radiative exciton life-times have been formulated. The nonlinear behaviour of temperature dependence of total life-time of exciton or the PL decay time has been indicated. At low temperatures, exciton decay is mainly due to radiative processes whereas at higher temperatures, it is by non-radiative channels. Therefore, the life-time of exciton, initially, increases with temperature, attains a maximum value and then decreases at high temperatures. The processes different from radiative free exciton recombination also play an important role and possibly, dominate the recombination mechanism as the temperature is raised.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 723-726

 

 

Study of dark and photoconductivity of
Sb-doped CuInSe2 thin films

Rakesh Kumar, Naresh Padha, P K Shishodi & R M Mehra

 

 

 

Dark and photoconductivity measurements of un-doped and Sb-doped CuInSe2 (CIS) films prepared by pulsed laser deposition technique, using ArF laser have been reported. The dark and photoconductivity of Sb-doped films have been found to be higher, compared to the un-doped CIS films. Recombination mechanism has also been discussed in the doped and un-doped films.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 727-730

 

 

Charge imbalance in a non-equilibrium superconductor

B A Mattoo

 

 

A general formalism for charge imbalance in a non-equilibrium superconductor is obtained using x-integrated Green’s function, which is applicable at arbitrary temperature, even when the width of quasi-particle states is appreciable due to pair breaking processes and when strong coupling effects are significant.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, September 2003, pp. 731-738

 

 

Effect of charge transfer behaviour on the
dielectric and ac conductivity of Co-Zn ferrite
doped with rare earth element

M A Ahmed & M H Wasfy

 

 

The dielectric constant and ac conductivity were measured for the ferrite samples Co1-xZnxLa0.25Fe1.75O4; 0.1≤x≤0.7 at different temperatures as a function of the applied frequency. The dielectric constant was interpreted on the basis of changing the enthalpy as well as the internal energy of the system. The orientational and rotational polarizations play a significant role in increasing the value of in the second temperature region. The conductivity results give more than one straight line, indicating the different conduction mechanisms. The electron hopping between the iron ions and the hole hopping between the cobalt ions are the main conduction processes in the investigated samples as it was enhanced from the drift mobility data. The values of the activation energy obtained, indicate the semiconducting behaviour of the samples.