Indian Journal of Pure and Applied Physics

 

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VOLUME 40                                                      NUMBER 5                                                        MAY  2002

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CONTENTS

 

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

Study of intermolecular interactions in binary liquid mixtures through ultrasonic speed measurement

      A Ali*, Y Yasmin & A K Nain

 

315

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

Transition assignment to Lb1 satellites in X-ray emission spectra of middle-Z elements

      S Poonia* & S N Soni

 

 

323

Photoelectrochemical (PEC) studies on chemically deposited Bi2Se3 thin films

      B R Sankapal, H M Pathan & C D Lokhande*

 

331

Thermoluminescence in ZnS:Pr and Zns: (Cu, Pr) phosphors

      A K Mishra*, L N Tripathi, U N Pandey & Sanjay K Mishra

337

Analytical two-dimensional model for pulsed doped InP-based lattice-matched HEMTs for high 

      frequency applications

      Ritesh Gupta, Mridula Gupta & R S Gupta*

 

342

Dielectric relaxation study of mixtures of 4-fluoroaniline and 1-propanol

      V A Rana, A D Vyas* & N M More

 

350

Mobile charge density wave model for third order non-linearity of  p–conjugate polymers

      Aranya B Bhattacherjee

 

355

X-ray crystallographic studies of polymeric materials

      N V Bhat & R R Deshmukh*

 

361

dc Resistivity behaviour in fly-ash

      S C Raghavendra*, R L Raibagkar & A B Kulkarni

367

Interdisciplinary Physics and Related Areas of Science and Technology

Recent advances in understanding magnetic emulsion stability

      John Philip*, R Kiran, T Jayakumar, P Kalyanasundaram & Baldev Raj

 

 

370

News Scan

Superconductivity and power transmission

      Poonam Bhatt

 

375

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

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 40, May  2002, pp. 315-322

Study of intermolecular interactions in binary liquid
mixtures through ultrasonic speed measurement

A Ali*, A Yasmin & A K Nain

Density r, and ultrasonic speed u, have been measured in pure benzyl alcohol (BA), cyclohexane, toluene and chlorobenzene and in their binary mixtures with BA as common component at 308 K. From these experimental data, isentropic compressibility Ks, intermolecular free length Lf, acoustic impedance Z, molecular association RA, molar sound speed Rm, excess isentropic compressibility KsE, excess free length LfE, excess acoustic impedance ZE, and excess ultrasonic speed uE are calculated for all the three binary liquid mixtures, over the entire composition range. The variations of these parameters, particularly the sign and magnitude of excess functions, with composition of the mixtures suggest dipole-induced-dipole interaction between BA and cyclohexane, and weak to medium-strength p---H bond between BA and chlorobenzene/toluene molecules. Theoretical values of ultrasonic speed in binary liquid mixtures are calculated using different theories and empirical relations. The relative merits of these theories and relations have been discussed.

 

Indian Journal of Pure & Applied Physics

Vol. 40, May 2002, pp.323-330

Transition assignments to Lb1 satellites in
X-ray emission spectra of middle - Z elements

S Poonia & S N Soni

 

The X-ray satellite spectra arising due to  (x º s,p,d) transition array, in elements with Z = 42-50, have been calculated. While the energies of various transitions of the array have been determined by using available HFS data on and  Auger transition energies, their relative intensities have been estimated by considering cross-sections of singly ionized  (x º s,p) states and then of subsequent Coster Kronig transitions and shake off processes. The calculated spectra have been compared with the measured satellite energies in Lb1 spectra. Their intense peaks have been identified as the observed satellite lines. One-to-one correspondence between the peaks in calculated spectra and the satellites in measured spectra has been established on the basis of the agreement between the separations in the peak energies and those in the measured satellite energies. It has been established that four satellites observed in the Lb1 region of the X-ray spectra of various elements and named b1I, b1II, b1III and b1IV in order of increasing energy are mainly emitted by  transitions. It is observed that only b1II in all these spectra can be assigned to super-position of 3F3-3F3 and 3F2-3F2 transitions and that this must be most intense of all these satellites. Each of remaining two satellites is found to have different origins in different elements. The possible contributions of other transitions of the  (x º s,p,d) array having appreciable intensities have also been discussed.

 

Indian J Pure & Applied Physics

Vol. 40, May  2002, pp. 331-336

Photoelectrochemical (PEC) studies on
chemically deposited Bi2Se3 thin films

B R Sankapal, H M Pathan & C D Lokhande*

Thin Film Physics Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004

Received 15 May 2001; revised 22 January 2002; accepted 13 February 2002

Semiconducting Bi2Se3 thin films have been prepared from aqueous alkaline bath onto fluorine-doped tin oxide (FTO) glass substrates (sheet resistance ~ 7 W-cm2) by chemical bath deposition (CBD) at room temperature (27 °C). The films formed are of nanocrystalline, smooth, homogeneous and well covered to the substrate surface as evidenced from X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies, respectively. These films are annealed at 200 °C for 4 hr in air. The annealed Bi2Se3 films are used for photoelectrochemical (PEC) characterization using polysulphide as an electrolyte and graphite as a counter electrode. The characteristics such as current-voltage (I-V), photovoltaic output and capacitance etc. have been studied and results are reported.

 

 

Indian Journal of Pure & Applied Physics

Vol. 40, May 2002, pp. 337-341

Thermoluminescence in ZnS:Pr and ZnS: (Cu,Pr) phosphors

A K Mishra, 1L N Tripathi, U N Pandey & 2Sanjaya K Mishra

Thermoluminescence (TL) and phosphorescence properties of ZnS:Pr and ZnS:(Cu,Pr) phosphors have been studied to determine the trapping parameters. TL studies have been made by a number of methods, namely initial rise method, Curie and various heating rate method. The decay constants have also been calculated from decay curves.

 

Indian Journal of Pure & Applied Physics

Vol. 40, May 2002, pp. 342-349

Analytical two-dimensional model for pulsed doped InP-based lattice-matched HEMTs for high frequency applications

Ritesh Gupta, Mridula Gupta & R S Gupta

An analytical two-dimensional model for pulsed doped HEMT is developed for InAlAs/InGaAs heterostructure using Greens function. Non-linear variation of sheet carrier density with quasi-Fermi energy is used to formulate the characteristics. The exact variation of sheet carrier density with gate voltage and the extension of gate boundaries with the variation of gate-to-drain and gate-to-source voltages are included in the analysis and the electric field profile has also been extensively studied considering the short channel effects. Results so obtained are in close proximity with published data.

 

Indian Journal of Pure & Applied Physics

Vol. 40, May 2002, pp. 350-354

Dielectric relaxation study of mixtures of
4-fluoroaniline and 1-propanol

V A Rana, A D Vyas & N M More

Complex permittivity of the mixtures of 4-fluoroaniline with 1-propanol has been measured at different temperatures using time domain reflectometry technique. The complex permittivity spectra are used to determine static dielectric constant es and relaxation time t by nonlinear least square fit method. With these parameters, excess dielectric properties, Kirkwood correlation factor and thermodynamical parameters have also been obtained. These evaluated parameters at different temperatures indicate strong interaction between 4-fluoroaniline and 1-propanol.

 

Indian Journal of Pure & Applied Physics

Vol. 40, May 2002, pp. 355-360

Mobile charge density wave model for third order
non-linearity of p- conjugate polymers

Aranya B Bhattacherjee

A theoretical one dimensional model based on Huckel’s molecular orbital theory applied to one electron de-localized p electron Hamiltonian in a conjugate chain of regular polyene (ignoring electron-electron repulsion) is developed. It demonstrates the dependence of third order non-linearity on the following: (a) the chain length, (b) linear correlation plot of n (C=C) versus 1/lmax (parameters measured from linear spectroscopic technique of Raman and absorption spectroscopy), (c) ratio of the electron velocity to the sound velocity in the chain and (d) deformation potential coupling of the phonons to the on-site electronic charge density.

 

Indian Journal of Pure & Applied Physics

Vol. 40, May 2002, pp. 361-366

X-ray crystallographic studies of polymeric materials

N V Bhat & R R Deshmukh

X-ray diffraction (XRD) studies are very useful for distinguishing crystalline and non-crystalline states. Highly crystalline substances give patterns with sharp diffraction peaks or spots, whereas liquids or amorphous materials lie between these two extremes, because their chain length is large and it is difficult to attain three-dimensional regularity. However, XRD studies of polymers yield interesting results. A large number of polymeric materials such as polyethylene, polypropylene, nylon, polyethylene terephthalate (PET), polyvinylidine fluoride etc. as well as natural polymers like, cotton and silk have been studied. The diffraction pattern usually consists of some sharp peaks together with broad halos. A careful analysis of the diffraction pattern allows us to find out the crystallite shapes, sizes and percentage crystallinity. The diffraction pattern is very sensitive to thermal history, chemical processing and other factors. In the present paper, the results of XRD of PET when subjected to thermal, chemical and plasma treatments have been presented. The results show that the percentage crystallinity can be varied from 17 to 50 %.

 

Indian Journal of Pure & Applied Physics

Vol. 40, May 2002, pp. 367-369

dc Resistivity behaviour in fly-ash

S C Raghavendra, R L Raibagkar & A B Kulkarni

The fly-ash (FA) sample has been collected from a 840 MW thermal power station, Raichur (Karnataka), with a daily FA production of 7000 tons. From the available elemental data analysis, further investigations on the electrical resistivity behaviour of circularly shaped disc of FA have been carried out in the temperature range 100-600 °C. It has been observed that resistivity is gradually decreasing with the increase of temperature. The electrical conductivity and activation energies have been estimated. The possible conductivity mechanism is discussed.

 

Indian Journal of Pure & Applied Physics

Vol. 40, May 2002, pp. 370-374

Recent advances in understanding magnetic emulsion stability

John Philip, R Kiran, T Jayakumar, P Kalyanasundaram & Baldev Raj

The recent advances in the understanding of magnetic emulsion stability, from force measurement studies and some of the interesting applications of stabilized magnetic emulsions have been presented. A newly developed force measurement technique, which facilitates the measurement of the forces between individual colloidal particles has been presented. The results on the forces between individual colloidal liquid droplets in the presence of different types of surfactants and a weak polyelectrolyte, poly acrylic acid (PAA) and one of the potential application of magnetic emulsions for non-destructive testing have been presented.

 

Indian Journal of Pure & Applied Physics

Vol. 40, May 2002, pp. 375-376

News ScanSuperconductivity and power transmission

Poonam Bhatt