Indian Journal of Pure and Applied Physics

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VOLUME 47	NUMBER 9	SEPTEMBER 2009
CODEN:IJOPAU 47(9) 613-686		ISSN:0019-5596

CONTENTS

General
Combined effects of Hall current and rotation on free convection MHD flow in a porous channel	617
K D Singh* & Rakesh Kumar
Magnetohydrodynamic boundary layer flow past a porous substrate with Beavers-Joseph boundary condition	624
R N Jat^* & Santosh Chaudhary
Atomic and Molecular Physics
UV-visible, infrared, Raman and ESR spectra of gamma-irradiated TiO2-doped soda lime phosphate glasses	631
Fatma H El-Batal
Surface morphological, band and lattice structural studies of cellulosic fiber coir under mercerization by ESCA, IR and XRD techniques	643
D N Mahato*, R N Prasad & B K Mathur
S-wave quarkonia spectroscopy in a relativistic quark model	648
Subrata Chakraborty* & Arun Kumar Roy
Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics and Fluid Dynamics
Enhanced sensitivity refractive index sensor based on segmented fiber with bending	655
Nahar Singh*, Vandana Mishra, Subhash C Jain, Sreekanth K V, G C Poddar & Pawan Kapur
Condensed Matter: Structural, Mechanical and Thermal Properties
Fractional quantum Hall effect in graphene	658
S Sahoo* & S Das
Pressure-volume relationships and bulk modulus for sodium halides	663
S S Kushwah * & N K Bhardwaj
Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Electrical and optical properties of poly(aniline-co-8-anilino-1-napthalene sulphonic acid) — A material for ESD applications	667
Vineet Bansal, Hema Bhandari, M C Bansal & S K Dhawan^*
Effect of Ga and Zn doping on coherent transition of YBCO superconductor	676
A Mohanta & D Behera*

Authors for correspondence are indicated by (*)

Indian Journal of Pure & Applied Physics

Vol. 47, September 2009, pp. 617-623

Combined effects of Hall current and rotation on free convection
MHD flow in a porous channel

K D Singh* & Rakesh Kumar¹

*Department of Mathematics (ICDEOL), H P University, Shimla 171 005

¹Department of Mathematics, Govt College for Girls (RKMV), Longwood Shimla 171 001

*E-mail: kdsinghshimla@gmail.com

Received 24 March 2009; revised 17 June 2009; accepted 31 July 2009

A theoretical analysis of an oscillatory free convective MHD flow of a viscous incompressible and electrically conducting fluid in a vertical porous channel in the presence of Hall current has been carried out. The two insulating porous plates are subjected to a constant injection and suction. A uniform magnetic field is applied in the direction normal to the plates. The entire system rotates about the axis normal to the plates with uniform angular velocity W. For small and large rotations, the dependence of the steady and unsteady resultant velocities and their phase differences on various parameters have been discussed in detail. The results show that both steady and unsteady resultant velocities increase rapidly from zero near the stationary plate and then approach to unity in the form of damped oscillations. For large values of rotations and injection/suction at the plates, a phase lag is also observed for both steady and unsteady phase angles.

Keywords: Oscillatory free convective flow, Rotating, Hall current, MHD flow

Indian Journal of Pure & Applied Physics

Vol. 47, September 2009, pp. 624-630

Magnetohydrodynamic boundary layer flow past a porous substrate with
Beavers-Joseph boundary condition

R N Jat^* & Santosh Chaudhary^**

^*Department of Mathematics, University of Rajasthan, Jaipur 302 004

^**Department of Mathematics, Malaviya National Institute of Technology, Jaipur 302 017

E-mail: khurkhuria_rnjat@yahoo.com, d11.santosh@yahoo.com

Received 6 March 2009; revised 18 May 2009; accepted 3 July 2009

The flow of an electrically conducting fluid past a porous substrate attached to the flat plate with Beavers-Joseph boundary condition under the influence of a uniform transverse magnetic field has been studied. Taking suitable similar variables, the momentum equation is transformed to ordinary differential equation and solved by standard techniques. The energy equation is solved by considering two boundary layers, one in the porous substrate and the other above the porous substrate. The velocity and temperature distributions along with Nusselt number are discussed numerically and presented through graphs.

Keywords: Magnetohydrodynamic, Boundary layer, Porous substrate

Indian Journal of Pure & Applied Physics

Vol. 47, September 2009, pp. 631-642

UV-visible, infrared, Raman and ESR spectra of gamma-irradiated
TiO₂-doped soda lime phosphate glasses

Fatma H El-Batal

Glass Research Department, National Research Center, Dokki, Cairo, Egypt

E-mail: fh_elbatal @yahoo.co.uk.

Received 13 February 2009; revised 14 May 2009; accepted 30 June 2009

Undoped and TiO₂-doped soda lime-phosphate glasses were prepared. UV-visible, infrared, Raman and electron spin resonance spectroscopic studies of the prepared samples, with varying compositions and increasing TiO₂ contents, were measured before and after successive gamma irradiation. The parent undoped glass reveals strong UV absorption originating from trace iron impurities. Experimental data indicate that titanium ions are involved in two valencies in such glasses, namely the trivalent and pentavalent states. The trivalent titanium (Ti³⁺) ions are characterized by its purple colour and showing characteristic two visible absorption bands and paramagnetic ESR character. The tetravalent titanium (Ti⁴⁺) ions belong to the d° configuration and possess only charge transfer ultraviolet absorption interfering with the UV bands due to trace iron impurities as evidenced in the undoped specimen. Glasses with high TiO₂ contents show retardation or shielding effect towards successive gamma irradiation. The changes in the UV, visible and infrared absorption spectra are interpreted in relation to the generation of induced defects by irradiation and the response of the change in glass composition or TiO₂ content. Raman and ESR measurements support the proposed interpretations of the experimental results.

Keywords: Soda lime phosphate glass, TiO₂, Gamma ray, UV-visible-Raman-ESR

Indian Journal of Pure & Applied Physics

Vol. 47, September 2009, pp. 643-647

Surface morphological, band and lattice structural studies of cellulosic
fiber coir under mercerization by ESCA, IR and XRD techniques

D N Mahato*, R N Prasad** & B K Mathur

Department of Physics, IIT, Kharagpur 721 301

*P G Department of Physics, Tata College, Chaibasa 833 202

** Department of Physics, J L N College, Chakradharpur

E-mail: dn.mahato08@yahoo.com

Received 4 March 2009; revised 29 May 2009; accepted 20 July 2009

The electron spectroscopy for chemical analysis (ESCA) studies show the increased binding energy (BE) of C_1s and O_1s on mercerization. The oxygen to carbon ratio increases. The cellulose I lattice structure is preserved, which is reflected in the XRD and IR spectra. These assume significance because these changes reflect in the structure-sensitive physical properties. The change in oxidation state is supported by 2929 cm^-1 band. The band at 1267 cm^-1 gives depolymerization. The IR band at 1433 cm^-1 gives idea of restriction of lattice transformation from cellulose I into cellulose II, which is confirmed by XRD pattern. The fiber undergoes disappearance of crystallinity, depolymerization and oxidation.

Keywords: Electron spectroscopy, Chemical analysis, ESCA, XRD, IR, Crystallinity, Oxidation, Depolymerization, Lattice transformation

Indian Journal of Pure & Applied Physics

Vol. 47, September 2009, pp. 648-654

S-wave quarkonia spectroscopy in a relativistic quark model

Subrata Chakraborty¹ & Arun Kumar Roy²

Department of Physics, Visva Bharati University, Santiniketan 731235

¹E-mail: subrata502002@yahoo.co.in

²E-mail: arun683@yahoo.com

Received 27 June 2008; revised 28 April 2009; accepted 30 June 2009

The S-wave spectroscopy of mesons in a relativistic quark model given recently for explaining the P-wave data of mesons has been studied.The recent data on S-wave spectroscopy can be explained by the relativistic modification of the scalar-vector model of confinement proposed earlier.

Keywords: Relativistic quark Model, QCD, Quarkonia, Quark confinement, S-wave mesons

Indian Journal of Pure & Applied Physics

Vol. 47, September 2009, pp. 655-657

Enhanced sensitivity refractive index sensor based on
segmented fiber with bending

Nahar Singh, Vandana Mishra, Subhash C Jain, Sreekanth K V, G C Poddar & Pawan Kapur

Central Scientific Instruments Organisation, Sector 30, Chandigarh 160 030

Fax No. : +91-172-2657267, 2657082; Phone No.: +91-172-2657811 Ext. 251

Received 13 April 2008; accepted 10 June 2009

a refractive index sensor fabricated by splicing segments of multimode and single mode fibers was investigated for enhanced sensitivity. The investigation revealed that when this sensor is used in bent position its sensitivity is improved by a factor of 5 to 10 depending on its bend curvature. It was found that the sensitivity is enhanced as the curvature is increased.

Keyword : Sensor, Refractive index, Sensitivity, Bend curvature

Indian Journal of Pure & Applied Physics

Vol. 47, September 2009, pp. 658-662

Fractional quantum Hall effect in graphene

S Sahoo¹ & S Das²

¹Department of Physics, National Institute of Technology, Durgapur 713 209, West Bengal

²Department of Electronics and Communication Engineering, Pailan College of Management and Technology
Bengal Pailan Park, Joka, Kolkata 713 104

E-mail: sukadevsahoo@yahoo.com

Received 29 September 2008; revised 16 April 2009; accepted 7 May 2009

The electrons in most of the conductors can be described by non-relativistic quantum mechanics but the electrons in graphene behave as massless relativistic particles, called Dirac fermions, though their speed is given by the Fermi velocity. The relativistic nature of the energy dispersion relation of electrons in graphene modifies the inter electron interactions. This results in the observation of a number of peculiar properties e.g. anomalous quantum Hall effect. We study the fractional quantum Hall effect (FQHE) in graphene. The quantized Hall conductivity in graphene in FQHE is shown to be:

,      where n = 0, 1, 2, 3 …

This fascinating result shows that the FQHE in graphene has a sequence of states which is different from the sequence found in the 2D electron gas.

Keywords: Fractional quantum Hall effect, Graphene, Landau levels, Half effect

Indian Journal of Pure & Applied Physics

Vol. 47, September 2009, pp. 663-666

Pressure-volume relationships and bulk modulus for sodium halides

S S Kushwah^a,* & N K Bhardwaj^b,**

^aDepartment of Physics, Rishi Galav College, Morena, 476 001, Madhya Pradesh

^bDepartment of Physics, Govt P G College, Morena, 476 001, Madhya Pradesh

*E-mail: sobrank@yahoo.com

**E-mail: niraj_bhardwaj@yahoo.com

Received 18 July 2008; revised 4 May 2009; accepted 29 June 2009

Equation of state for solids developed by Kushwah et al. [Physica B, 388 (2007) 20] has been used here to determine the pressure-volume relationships, bulk modulus and its pressure derivatives for NaF, NaCl, NaBr and NaI solids. The results are found to present close agreement with the experimental data. The results for P, K and dK/dP at different compressions have been used to study the relationship between dK/dP and P/K.

Keywords: Equation of state, Pressure-volume relation, Pressure derivatives, Sodium halides, Bulk modulus

Indian Journal of Pure & Applied Physics

Vol. 47, September 2009, pp. 667-675

Electrical and optical properties of poly(aniline-co-8-anilino-1-napthalene sulphonic acid) — A material for ESD applications

Vineet Bansal^1,2, Hema Bhandari¹, M C Bansal² & S K Dhawan^1*

¹Polymeric & Soft Materials Section, National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110 012

²Department of Physics, M M H College, Ghaziabad 201 009

*E-mail: skdhawan@mail.nplindia.ernet.in

Received 22 January 2009; accepted 12 June 2009

The homopolymer of aniline (An) and its copolymer with 8-anilino-1-napthalene suplhonic acid (8-ANSA) was synthesized by chemical oxidative as well as electrochemical polymerization process in the presence of para-toluene sulphonic acid (PTSA) as a dopant. The spectral, thermal, morphological and electrochemical properties of PTSA doped polyaniline and its copolymer (An-co-8-ANSA) were studied and compared to elucidate the effect of the inclusion of
8-ANSA in the copolymer feed. The resultant copolymer showed better solubility and processibility but this approach usually results in the lowering of conductivity, hence the ratio of aniline and 8-ANSA in the copolymer feed was selected to 80:20. The room temperature conductivity of the PTSA doped polyaniline (PANI-PTS) and poly(An-co-8-ANSA) in 80:20 was found to be in the order of 1.74 S/cm to 9.77×10^-1 S/cm, respectively. Conductivity mechanism of charge transport has been investigated in the range 30-300K. In the temperature range 30-70 K, copolymer showed tunneling mechanism. However, above 70 K conductivity attributes to Mott^’s variable range hopping (VRH) mechanism. The electrochemical behaviour of the polymers was studied by cyclic voltametry. The structure of the copolymer is characterized by ¹H NMR spectroscopy, UV-visible and FTIR spectroscopy. Electrostatic charge dissipation (ESD) of the conducting copolymer blend was also studied by blending of 1% of PTSA doped polyaniline and poly(aniline-co-8-ANSA) with LDPE which shows a static decay time of 0.1 to 0.25 sec on dissipating the charge from 5000 to 500 V.

Keywords: Conducting polymer, Polyaniline, Poly(aniline-co-8-anilino-1-napthalenesulphonic acid), Conductivity, Electrostatic charge dissipation

Indian Journal of Pure & Applied Physics

Vol. 47, September 2009, pp. 676-680

Effect of Ga and Zn doping on coherent transition of YBCO superconductor

A Mohanta & D Behera*

Department of Physics, National Institute of Technology, Rourkela, 769 008

*E-mail: dhrubananda_behera@yahoo.in

Received 3 February 2009; revised I June 2009; accepted 13 July 2009

The simultaneous incorporation of Ga³⁺ and Zn²⁺ to the Cu-site of YBa₂Cu₃O_7-δ has been analyzed for microstructural and electrical properties. Temperature-dependent electrical resistivity, X-ray diffraction and SEM analysis of a set of YBa₂(Cu_0.95Zn_0.05-xGa_x)₃O_7-y films prepared by solid state reaction technique have been investigated to study the substitutional effects of Ga and Zn at chain and plane site of Cu, respectively. The redistribution of charges in the superconducting system due to oxygen content and the resistance of the weak-links related inhomogeneities give rise to T_c degradation and dual values of exponents in the T_c0 region. The exponent values for fluctuation conductivity in the T_c0 region decrease with increase of substitution concentration. The dual exponent character shows that the intergranular weak links develop more resistance with increasing impurities.

Keywords: Superconductors, Excess conductivity, Coherence transition