Indian Journal of Pure and Applied Physics

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Volume 45

Number 11

NOVEMBER 2007

 

 

 

CODEN: IJOPAU 45 (11) 871-938

ISSN: 0019-5596

  

CONTENTS

 

Nuclear Physics

 

Study of radon and its progeny levels dwellings of Thankassery, Kerala

877

Rajesh Kumar*, A K Mahur, P J Jojo & Rajendra Prasad

 

Radon-thoron and their progeny dosimetry in the environment of LPG bottling plant using plastic
track detectors

880

S B Upadhyay, K Kant, Rekha Joshi, R G Sonkawade, S K Chakarvarti* & G S Sharma

 

Atomic and Molecular Physics

 

Vibrational spectra and normal coordinate analysis of adrenaline and dopamine

884

S Gunasekaran*, R Thilak Kumar & S Ponnusamy

 

Nonlinear optical parameters of Raman scattered mode in weakly polar magnetized
semiconductor-plasma

893

M Singh, P Aghamkar* & S Duhan

 

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

 

Pattern recognition analysis of acoustic emission signals propagated through a waveguide —
A simulation study

900

K Prabakar & S P Mallikarjun Rao*

 

Physics of Gases, Plasmas and Electric Discharges

 

Plasma enhanced vapour deposition grown cold cathode emits high current density

906

P Kumar, S Pal, S Gautam, P Chaturvedi, P Verma, J S B S Rawat, Harsh*,
P Ghosal & P K Bhatnagar

 

 

 

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

 

Electrical conduction behaviour of pristine and 100 MeV Ni ion irradiated polyethylene terephthalate/0.8poly(p-hydroxy benzoic acid) polymer liquid crystals

910

J K Quamara*, Y Sridharbabu & Geetika Goyal

 

Anomaly in optical thickness monitoring of a quarterwave thin film multilayer stack Its cause
and how to avoid it

920

A Basu

 

Dielectric dispersion in PbO-PbF2-B2O3 glass system doped with Cr2O3

926

A Veerabhadra Rao, M Srinivasa Reddy, V Ravi Kumar & N Veeraiah*

 

 

 

___________

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


Indian Journal of Pure & Applied Physics

Vol. 45, November 2007, pp. 877-879

 

Study of radon and its progeny levels dwellings of Thankassery, Kerala

 

Rajesh Kumar+, A K Mahur, P J Jojo* & Rajendra Prasad

Department of Applied Physics, Z H College of Engineering & Technology, Aligarh Muslim University Aligarh 202 002

*Department of Physics, Fatima Mata National College, Kollam 691 001

Received 16 November 2006; accepted 11 July 2007

Radon monitoring has become a global phenomenon due to its health hazard effects on population. 222Rn and its radioactive daughters present in the environment results into the largest contribution to the average effective natural radiation dose received by human beings. Indoor 222Rn exposure to the population depends in a complex way on the characteristics of the soil, the building structure, meteorology, ventilation conditions and occupants behaviour. LR-115 type II Solid State Nuclear Track Detectors (SSNTDs) have been used for the measurements of indoor radon concentration in 24 rooms in some in dwellings situated in Thankassery town along the south west coast of Kerala to carry out the assessment of the variability of expected radiation exposure of the population due to radon and its progeny. The town is situated near the high background area of Kerala. Radon concentrations are found to vary from 44.3 to 373.3 Bqm-3 with an average of (144.7 ± 61.5) Bqm-3 whereas the annual effective dose equivalents vary from 1.7 to 14.2 mSv with an average of (5.5 ± 2.3) mSv.

Keywords: Indoor radon, Solid State Nuclear Track detector, Etching, Alpha tracks

IPC Code: G01T

 

Indian Journal of Pure & Applied Physics

Vol. 45, November 2007, pp. 880-883

 

Radon-thoron and their progeny dosimetry in the environment of LPG bottling plant using plastic track detectors

S B Upadhyaya, K Kantb, Rekha Joshib, R G Sonkawadec, S K Chakarvartid & G S Sharmaa

aDepartment of Physics, B S A College, Mathura (U P)

bDepartment of Physics, KL Mehta Dayanand College for Women, Faridabad (Haryana) 121 001

cInter University Accelerator Centre, Post Box - 10502, New Delhi 110 067

dDepartment of Applied Physics, NIT, Kurukshetra 136 119

Received 27 July 2006; revised 17 January 2007; accepted 5 September 2007

The inhalation dose rates and annual effective dose contribution from the mixed field of radon and thoron present in the environment of LPG bottling plant were measured, as it is very much essential from health and hygiene point of view of the workers in the plant. The radon and thoron concentration and the inhalation dose were found to vary from 7.78±2.02 to 59.01±5.57 Bq/m3, 1.16±0.28 to 65.08±5.09 Bq/m3 and 0.23 to 2.29 mSv/y, respectively. The concentration of radon daughters was found to vary from 0.84 to 6.38 mWL, the concentration of thoron daughters from 0.03 to 1.76 mWL, the annual exposure due to radon and thoron daughters, collectively, from 0.036 to 0.273 WLM, the life time fatality risk from 0.11 ×10-4 to 0.82 ×10-4 and the annual effective dose from radon and thoron (PAEC) from 0.14  to 1.06 mSv/y.

Keywords: Radon, Thoron, Progeny, Inhalation dose, LPG, Health, Plastic track detectors

IPC Code: C01B 23/00, G01T, H01L

 

 Indian Journal of Pure & Applied Physics

Vol. 45, November 2007, pp. 884-892

Vibrational spectra and normal coordinate analysis of adrenaline and dopamine

 

S Gunasekaran, R Thilak Kumar1 & S Ponnusamy2

PG & Research Department of Physics, Pachaiyappa’s College, Chennai - 600 030, Tamilnadu

1Department of Physics, St.Joseph’s College of Arts & Science, Cuddalore 607 001, Tamilnadu

2Department of Physics, SRM University, Kattankulathur, Kancheepuram 603 203, Tamilnadu

1E-mail: manojthilak @yahoo.com

Received 8 November 2006; revised 17 May 2007; accepted 6 July 2007

The FTIR and FTRaman spectra for adrenaline and dopamine have been recorded over the region 4000-400 cm-1 and 3500-50 cm-1. Both adrenaline and dopamine molecules belong to the Cs point group. A generalised set of symmetry coordinates has been constructed and hence, potential constants have been evaluated using Wilson’s F-G matrix method. Potential energy distribution has also been calculated for the normal modes of vibration to check whether the chosen set of vibrational frequencies contribute maximum to the potential energy associated with the normal coordinates of the molecule.

Keywords: Adrenaline, Dopamine, FTIR, FTRaman spectra, Normal coordinate analysis, Potential energy distribution

IPC Code: G01J3/28

 

 

Indian Journal of Pure & Applied Physics

Vol. 45, November 2007, pp. 893-899

 

Nonlinear optical parameters of Raman scattered mode in weakly polar magnetized semiconductor-plasma

M Singh, P Aghamkar* & S Duhan

Department of Applied Physics,Guru Jambheshwar University of Science & Technology, Hisar 125 001

E-mail: msgur_18@yahoo.com

Received 16 October 2006; revised 30 May 2007; accepted 18 September 2007

This paper presents an analytical investigation of nonlinear absorption coefficient and refractive index of the Raman scattered stokes mode resulting from the nonlinear interaction of an intense pumping light beam with molecular vibrations of semiconductor-plasma. The origin of this nonlinear interaction lies in the third-order (Raman) susceptibility arising from the induced current density and density fluctuations generated within the medium. The total refractive index and absorption coefficient are determined through the effective susceptibility derived with the help of coupled-mode theory of plasmas. The effect of Szigeti effective charge (q) and magnetic field (b0) has been introduced through equation of motion of lattice vibration and Lorentz force, respectively. The numerical estimates are made for n-type InSb crystal duly irradiated by a
10-nanosec pulsed 10.6 μm CO2 laser. The Szigeti effective charge contributes the Raman susceptibility at moderate excitation intensity. At high excitation intensity, the contribution of Szigeti effective charge is wiped off and nonlinearity in the medium is only due to differential polarizability. In the absence of Szigeti effective charge, the magnitude of Raman susceptibility is found to agree with other theoretical quoted values. The analysis establishes that a small absorption coefficient and large refractive index can easily be obtained by proper selection of magnetic field and doping concentration under moderate excitation intensity in weakly polar semiconducting crystals which proves its potential as candidate material for the fabrication of cubic nonlinear devices.

Keywords: Nonlinear absorption, Refraction, Stimulated Raman scattering, Magnetic field, Weakly polar III-V
                     semiconductors

IPC Code:   G02F1/35

Indian Journal of Pure & Applied Physics

Vol. 45, November 2007, pp. 900-905

 

 

Pattern recognition analysis of acoustic emission signals propagated
through a waveguide – A simulation study

K Prabakar & S P Mallikarjun Rao

Acoustic Emission Lab., Physics Department, University College of Science,
Osmania University, Hyderabad 500 007

E-mail: <spmrao@yahoo.com>

Received 27 July 2006; revised 2 August 2007; accepted 18 September 2007

Pattern recognition (PR) analysis of acoustic emission (AE) signals for classifying the source mechanisms involved, is a widely accepted practice, if the signals are directly picked up from the test specimen. However, there is an apprehension for the same, when a waveguide (WG) is used to pickup the signals. In the present paper, the validity of PR analysis has been studied on burst AE signals even after their propagation through a WG, using a software routine for wave propagation in cylindrical rods, based on Pochhammer-Chree (PC) equations, developed by Seco F et al. “PCDISP: a tool for the simulation of wave propagation in cylindrical waveguides”, In: The 9th international congress on sound and vibration, in Orlando, Florida (2002). It is found that irrespective of the dimensions of the cylindrical WG, PR analysis can classify different source mechanisms. An experiment to support the simulation is also included.

Keywords: Pattern recognition, Acoustic emission, Cylindrical waveguide

IPC Code: B06B

Indian Journal of Pure & Applied Physics

Vol. 45, November 2007, pp. 906-909

 

Plasma enhanced vapour deposition grown cold cathode emits high current density

P Kumar, S Pal, S Gautam, P Chaturvedi, P Verma, J S B S Rawat & Harsh

Solid State Physics Laboratory, Lucknow Road, Delhi 110 054

and

P Ghosal

Defence Metallurgical Research Laboratory, Hyderabad 500 058

and

P K Bhatnagar

Delhi University, South Campus, Delhi 110 021

Received 8 November 2006; accepted 30 August 2007

The high aspect ratio of the carbon nanotube (CNT) (of the order of 10,000) coupled with novel electrical, mechanical and thermal properties of the CNT make them very attractive candidate for cold cathode application in high power vacuum devices. Such CNT based cold cathode (CCC) can provide large and stable emission current densities at reasonably low field and can be switched on and off instantaneously with no limitation on grid modulation. These CCC based vacuum devices can also be efficiently operated under harsh ambient conditions and therefore, ideally suited for air borne and space applications. In this paper, the development of CCC using vertically aligned matrix of carbon nanotubes with optimum tip density grown by chemical vapour deposition (CVD) and plasma enhanced vapour deposition (PECVD) technique on silicon substrate has been reported. The field emission characteristics of a typical CCC grown via CVD and PECVD were compared. The field emission current density obtained in case of CVD sample was 8 mA/cm2 at a field of 3.6 V/μm while it was 35 mA/cm2 at the same field in case of PECVD grown CCC. The emission current in most of the samples was found to be stable over long period of time. Our measurements suggest great promise for achieving high current densities at practical electric fields.

Keywords: Carbon nanotube, Plasma enhanced vapour deposition, Cold cathode

IPC Code: H05H, H01F41/30

 

Indian Journal of Pure & Applied Physics

Vol. 45, November 2007, pp. 910-919

 

Electrical conduction behaviour of pristine and 100 MeV Ni ion irradiated
PET/0.8PHB polymer liquid crystals

 

J K Quamara*, Y Sridharbabu**, Geetika Goyal & Anu Sharma

Department of Applied Physics, National Institute of Technology, Kurukshetra 136 119

Received 19 February 2007; accepted 18 Sepember 2007

Electrical conduction behaviour of pristine and 100 MeV Ni ion irradiated terephthalate (PET)/0.8 poly(p-hydroxy-benzoic acid) (PHB) polymer liquid crystals has been investigated in transient and steady state conditions at different electric fields (13-104.3 kV/cm) and temperatures (40-250°C). The various mechanisms responsible for charge transport phenomena can be thoroughly investigated by studying temperature and field dependent conduction behaviour. The origin of transient currents in polymers has been ascribed to number of mechanisms. The dipolar relaxation seems to be the major contributor to these currents at lower temperatures. The temporal decay of current may be due to trapping of charge carriers and/or due to the reduction of electric field owing to the formation of Schottky layers in the vicinity of the electrodes. The high temperature relaxations do not contribute much to the transient behaviour. The transient currents in ion irradiated samples are mainly governed by cross-link structures and free radical formation in addition to the d-transition. Poole-Frenkel and Schottky conduction mechanisms appear to operate at high and low temperature regions, respectively, for both pristine and irradiated samples.

Keyword: Liquid crystals, Electrical conduction, Pristine, Polymer

IPC Code: C30B

Indian Journal of Pure & Applied Physics

Vol. 45, November 2007, pp. 920-925

 

 

Anomaly in optical thickness monitoring of a quarterwave thin film
multilayer stack — Its cause and how to avoid it

 

A Basu

Division of Electronic Materials, National Physical Laboratory, New Delhi 110 012

E-mail: abasu@mail.nplindia.ernet.in

Received 13 March 2007; accepted 18 September 2007

During the optical monitoring of a quarterwave thin film optical multilayer stack being deposited sequentially on a substrate in a deposition chamber, the intensity of the light beam transmitted through or reflected from the monitoring plate goes through a series of turning points (maxima and minima). The deposition of a film is stopped at a turning point in order to obtain a quarterwave thick film at the monitoring wavelength. In most of the cases, the maxima and minima occur sequentially. However, during the deposition of some quarterwave multilayer stacks a maximum is not followed by a minimum (or vice versa) during the deposition of successive films. Rather, the intensity may change slightly in the opposite direction to that which is expected or not change appreciably, making the monitoring of the deposited film thickness difficult, if not impossible. This occurs when the effective refractive index of the multilayer stack is very close to the refractive index of the film to be deposited next. Either an alternative method of monitoring the thickness of that particular film has to be adopted, or fresh monitoring plates have to be used at crucial stages during the sequential deposition of the multilayer stack.

Keywords: Optical thickness monitoring, Thin film, Multilayer stack, Quarterwave, Turning points, Refractive index,
 Transmittance

IPC Code: G01B11/06, G01B15/02, G01B21/00 121:02

Indian Journal of Pure & Applied Physics

Vol. 45, November 2007, pp. 926-934

Dielectric dispersion in PbO-PbF2-B2O3 glass system doped with Cr2O3

 

A Veerabhadra Rao, M Srinivasa Reddy, V Ravi Kumar & N Veeraiah*

Department of Physics, Acharya Nagarjuna University PG Centre, Nuzvid 521 201

*E-mail: nvr8@rediffmail.com

Received 5 December 2006; revised 9 August 2007; accepted 18 September 2007

PbO-PbF2-B2O3 glasses containing different concentrations of chromium ions (introduced as Cr2O3) ranging from 0 to 0.4 mol % were prepared. The dielectric properties i.e., constant e¢, loss tand, ac conductivity sac over a range of frequency and temperature of Pb glasses have been carried out. The results have been analyzed in the light of different oxidation states of chromium ions with aid of the data on differential scanning calorimetry, infrared, optical absorption and ESR spectra. The analysis indicates that when the concentration of chromium ions is up to ~ 0.3 mol %, these ions mostly exist in Cr3+ state, occupy network-modifying positions with CrO6 structural units and at about 0.4 mol % a part of chromium ions seems to exist in Cr6+ state, adopting network forming positions with CrO42-structural units and causing an increase in the insulating strength of the glass.

Keywords: Glasses, Dielectric properties, Optical absorption, ESR, IR spectra

IPC Code: GOIR 27/26, F21K 2/04