Vol 9 No 1

Asian Journal of Physics

Vol 9, No 1, (2000)

CONTENTS

Simple variational principle I : Theory and application to thermoelectric phenomena

Christopher G Jesudason 1

Photothermal spectroscopy and its application in characterisation of polycyclic aromatic hydrocarbons

R K Garg and Pardeep Kumar 15

Techniques and applications of electron paramagnetic resonance spectroscopy

S K Gupta 31

Force field for planar modes of fluorobenzene revisited

J S Singh, D N Singh and R A Yadav 45

Spectroscopic studies of iron doped B₂0₃-Bi₂0₃ glasses

L Baia, D Maniu, T Iliescu,S Simon, S Schlücker and W Kiefer 51

I-V and C-V measurements on Al₂0₃ based MOS structures. 59

A C Sarmah and K C Barua

Mechano and electroluminescence spectroscopy of Cu and Mn doped ZnS phosphors

R S Gupta, S P^.Tamrakar, S K Sharma and B P Chandra 67

An approach for efficiency determination of HPGe detectors used in γ-ray spectroscopy techniques

N Walley El-Dine 71

Structural studies of some polar molecular systems using microwave absorption technique and nuclear magnetic resonance

S K Vaish and N K Mehrotra 79

Lattice dynamics of tellurium subchloride- A Raman study

Y S Raptis, E Anastassakis and A Topalidou 85

Ionic character and dipole moments of alkali halides from their electronegativity data

K P R Nair and Usha John 93

Correlative study of interplanetary plasma parameters during the period of 1978-83

V K Mishra, D P Tiwari and Pankaj K Shrivastava 97

An evaluation of temperature dependent electrical resistivity ρ(T) and thermoelectric power S(T) for TiS₂, Co_x,TiS₂ and Ni_xTiS₂

M P Jha, A Singh and L K Mishra. 103

Optical limiting and nonlinear absorption studies in Bi₁₂SiO₂₀ crystal at high power nanosecond laser regime

P Sreeramana Aithal, R P Singh, P Prem Kiran and D Narayana Rao 107

Structural and dielectric properties of Sr₅RTi₃Nb₇O₃₀ [R = Nd, Eu, Gd and Dy] ceramics

A Panigrahi, R N P Choudhary and B N Das 115

Quantum mechanical study of CP violation

Vinita Sahoo and K P Sahu 119

Conversion electron lines of a new gamma transition of 1.51 MeV in the decay of ²⁰⁷Bi

R K Mishra, A Kumar, Shashi Prabha and S P Tiwari 121

Growth features and dislocation etching of In Bi_0.8Se_0.2

G R Pandya, K R Shah and S M Vyas 124

Asian Journal of Physics Vol. 9, No 1 (2000) 45-50

Force field for planar modes of flurobenzene revisited

J S Singh,D N Singh and R A Yadav*

Department of Physics, Laser and Spectroscopy Lab, Banaras Hindu University, Varanasi-221 005, (India)

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The force field calculations for planar modes of flurobenzene have been revisited using more accurately observed values of fundamentals [J Mol Spectrosc, 73 (1978)290] of parent molecule and its two deuterated analogues namely, flurobenzene –p-d and –d⁵. A 38 parameters force field has been determined leading to alteration of the earlier vibrational assignments for some of the normal modes. The doblet observed at 2274.4 and 2304.4cm^-1 as A type IR bands for p-d fluorobenzene could be explained as arising due to the Fermi resonance between the (C-D) fundamental and the first overtone of the CHplanar bending mode observed at 1156 cm^-1. Three force constants for the stretching of the c-c bonds of the ring have been taken in view of the C2v symmetry and similarly, 3 force constants for the CH stetchings and the bendings and 4 force constants for the planar ring bendings have been taken . It is found that the force constants involving different C-C bond stetchings vary within 2%, those involving CH strechings and bendings vary within 1% and 7.5% respectively . However, the force constants involving the ring bendings show rather a large variation of 28%.

Total Refs : 10

Asian Journal of Physics Vol 9, No 1 (2000) 51-57

Spectroscopic studies of iron doped B₂0₃-Bi₂03 glasses

L BAIA, D MANIU, T ILIESCU and S SIMON^*

Babes—Bolyai University, Physics Department, 3400, Cluj—Napoca, Romania

And
S SCHLUCKER and W KIEFER^*
Institut fur Physikalische Chemie, Universitat Wurzburg, Am Hubland, D-97074 Wiirzburg, Germany

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Raman and IR spectra of 99.5%[xB₂0₃(1—x)Bi₂0₃]0.5%Fe₂0₃ glasses with different Bi/B nominal ratios (0.20 ≤ x ≤ 0.80) have been investigated. The influence of bismuth atoms on the vitreous B₂0₃ network as well as the local order changes both around bismuth and boron atoms are studied. The very low content of Fe₂0₃ introduced in these samples has no structural effect on the bismuth-borate glass matrices as far as evidenced by the methods used.

Total Refs : 27

Asian Journal of Physics Vol. 9, No 1 (2000) 107-114

Optical limiting and nonlinear absorption studies in Bi₁₂SiO₂₀ crystal at high power nanosecond laser regime

P Sreeramana Aithal, R P Singh, P Prem Kiran and D Narayana Rao

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Nonlinear absorption properties of Bi₁₂SiO₂₀ (BSO ) crystal are studied using single beam Z-scan technique in the nanosecond regime without applying external electric field. We observed a strong nonlinear absorption at 532 nm (SHG of an Nd: YAG laser) and at 595nm (Nd:YAG pumped dye laser) . We have also studied the optical limiting and the laser damage threshold of the crystal at both the wavelengths. A physical model is developed to explain the observed behavior using photorefractive properties of BSO crystal which incorporates the accumulative trap assisted excited state absorption and the instantaneous two-photon absorption which makes it as an excellent optical limiter.

References: 15

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ASIAN JOURNAL OF PHYSICS