021232   Chakrabarti S (Maharaja Mahindra Chandra College, 20, Ramkanto Bose Street, Kolkata-700 003) : Convenient method for measuring the refractive indieces and estimation of some microscopic parameters of glass prism. Phys Educ 2006, 23(3), 167-74.

bhen the refractive index(RI) of a glass prism is measured for various spectral lines from a polychromatic source, the prism has to be placed at the minimum deviation position for each colour in the conventional method. A more convenient way is to place the prism at a suitable position once and for all and to measure the deviations of all lines together with the angle of incidence. Once can calculate the RIs with an accuracy comparable to that achieved by measuring the minimum deviation in the conventional method. With an accurate measurement of the RIs, one can estimate several interesting parameters of the glass prism including its molecular polarizability.

2 illus, 3 tables, 3 ref

021231   Bayari A;Karakaplan M (Physics Dep, Science and Arts Faculty, Adiyaman Univ, Adiyaman, Turkey, Email: abayri@inonu.edu.tr) : Theoretical approach to the magnetic properties of Mn(II), Cr(III), and Cu(II) complexes in the newly reported 12- and 15-membered macrocyclic ligands. Pramana J Phys 2007, 69(2), 301-6.

The magnetic properties of Cu²⁺, Cr³⁺, and Mn²⁺ ions in the newly reported 12- and 15-membered macrocyclic complexes are analysed by a theoretical approach. The calculated magnetic moment and magnetic anisotropy for various situations, especially for Cu(II) ion, suggest that the magnetic properties may lead to a better interpretation about the geometry. It is also suggested that the zero-field splitting Hamiltonian may be used for magnetic properties of some metal ions, which have orbital singlet ground term in these complexes.

28 ref

021230   Ayish Begam A;Radhakrishnan R;Premnazeer K (Physics Dep, Avinashilingam Univ, Coimbatore-641 043) : Effect of moisture on d.c. conductivity of polyaniline composite films. Ultra Scient phys Sci 2007, 19(2), 189-94.

Conductive Polyaniline-PMMA composite films have been prepared by solution casting technique onto well-cleaned glass substrates. Metal - Polymer composite - Metal sandwich structure was used to measure the d.c. conductivity of unannealed and annealed polyaniline - PMMA composite films in the temperature range of 303-373 K. Presence of moisture enhances the conductivity by one to three orders in the unannealed films compared to annealed films. The effect of moisture on d.c conductivity and the moisture expulsion range (340-360 K) were discussed.

3 illus, 15 ref

021229   Anila A K;Thirumagalath S;Sethumadhavan P; Renuka G;Issac M (Physics Dep, S.N.G. College, Calicut) : Variation of convective loss cone instability (LCI) in magnetic mirror. Ultra Scient phys Sci 2007, 19(2), 291-4.

The loss cone instability growth rate expression is established. Computational work on the growth rate was carried out. The variation of growth rate of LCI with thermal velocity and loss cone index was studied and found to be in good agreement with other works. It was established the instability will arise only if j ≥3.

2 illus, 3 ref

021228   Al-Khattabi L A (Physics Dep, Faculty of Science, King Abdulaziz Univ, Jeddah (Saudi Arabia)) : Vacuum-to-vacuum transition amplitude using path integral quantization and Fenman rules for scalar fields. Ultra Scient phys Sci 2007, 19(2), 295-312.

The quantization of the field by path integral quantization enable as to find the propagator of sealer or Spinor field. The vacuum-to-vacuum transition amplitude could be represented diagrammatically in terms of Feynmarn diagrams we found that there is agreement between the diagrammatic representation statistically and the integrated result in the n-point functions for free field theory.

5 ref

021227   Ahmed A;Watts S J;HolmesSiedle A;Matheson J; Chowdhury M A H (Physics Dep, Shahjalal Univ of Science and Technology Sylhet, Bangladesh) : Comparison of introduction rates of defects produced in various silicon diode after proton and gamma irradiation. Ultra Scient phys Sci 2007, 19(2), 157-66.

Various diodes of different processing and manufacturer were studied using Deep Level Transient Technique (DLTS) after proton and gamma irradiation. Various defects observed in proton and gamma irradiated samples were differed only in the relative concentrations. The cluster-related defects didn't observed after gamma irradiations and only the impurity-related defects were observed with gamma radiation. The defect introduction rates were compared for various materials. The defect introduction rates at the Sintef standard diode was found to smaller compared to other diodes. Therefore the Sintef standard diode is more radiation hard. It is found that the radiation hardness is dependent on the processing of the diodes.

7 illus, 2 tables, 16 ref

021226   Aggarwal K M;Keenan F P (Astrophysics Research Centre, School of Mathematics and Physics, Queen's Univ Belfast, Belfast BT7 1NN, Northern Ireland, UK, Email: K.Aggarwal@qub.ac.uk ) : Collision strengths for transitions in Ni XIX. Pramana J Phys 2007, 69(2), 209-18.

Presents calculations of electron impact excitation collision strengths for transitions among the 89 fine-structure levels of the 2s²2p⁶, 2s²2p⁵3l, 2s2p⁶ 3l, 2s²2p⁶4l, and 2s2p⁶ 4l configurations of Ni XIX, for which flexible atomic code (FAC) has been adopted. Comparisons are made with the earlier available results in the literature, and the anomalies observed have been discussed.

3 illus, 1 table, 28 ref

020319   Zhang J M;Wang B;Xu K W (College of Physics and Information Technology, Shaanxi Normal Univ, Xian 710062, Shaanxi, People's Republic of China) : Surface segregation of the metal impurity to the (100) surface of fcc metals. Pramana J Phys 2007, 69(4), 603-16.

The surface segregation energies for a single metal impurity to the (100) surface of nine fcc metals (Cu, Ag, Au, Ni, Pd, Pt, Rh, Al and Ir) have been calculated using the MAEAM and molecular dynamics (MD) simulation. The results show that the effect of the surface is down to the fourth-layer and an oscillatory or monotonic damping (|E₁| <62> |E₂| <62> |E₃| <62> |E₄|) phenomenon in segregation energy has been obtained. The absolute value of the segregation energy E₁ for a single impurity in the first atomic layer is much higher than that in the nether layers. Thus, whether the surface segregation will work or not is mainly determined by E₁ which is in good relation to the differences in surface energy between the impurity and host crystals ΔQ = Q_imp-Q_hos. So we conclude that an impurity with lower surface energy will segregate to the surface of the host with higher surface energy.

1 illus, 3 tables, 69 ref

020318   Zaki M F;El-Shaer Y H (Experimental Nuclear Physics Dep, Nuclear Research Center, Atomic Energy Autority, P.O. Box 13759 Abu Zaabal, Cairo, Egypt, Email: moha1016@yahoo.com) : Particularization of alpha contamination using CR-39 track detectors. Pramana J Phys 2007, 69(4), 567-74.

Solid-state nuclear track detectors have found wide use in various domains of science and technology, e.g. in environmental experiments. The measurement of alpha activity on sources in an environment, such as air is not easy because of short penetration range of alpha particles. Furthermore, measurement of alpha activity by most gas ionization detectors suffers from high background induced by the accompanying gamma radiation. Solid state nuclear track detectors (SSNTDs) have been used successfully as detecting devices and as a passive system to detect alpha contamination on different surfaces. This work presents the response of CR-39 (for two types) to alpha particles from two sources, ²³⁸Pu with energy 5 MeV and ^241, Am with energy 5.4 MeV. The methods of etching and counting are investigated, along with the achievable linearity, efficiency and reproducibility. The sensitivity to low activity and energy resolution are studied.

6 illus, 1 table, 18 ref

020317   Zakharenko A A (NO, International Institute of Zakharenko Waves, 660037, Krasnoyarsk-37, 17701, IIZWs, Krasnoyarsk, Russia, Email: aazaaz@inbox.ru) : Creation evidence of the second non-dispersive Zakharenko wave by helium atomic beams in superfluid helium-II at low temperatures. Pramana J Phys 2007, 69(4), 617-29.

Experimental results of the creation of the second non-dispersive Zakharenko wave (C_ph = C_g ≠ 0) in the negative roton branch (the so-called second sound) of the bulk elementary excitations (BEEs) energy spectra are introduced. Several BEE signals detected by a bolometer situated in the isotopically pure liquid helium-II at low temperatures ~100 mK are shown, which give evidence of negative roton creation in the liquid by helium atomic beams striking the liquid surface. The negative roton signals were clearly distinguished by the following ways: the negative roton signal created by helium atomic beams appeared earlier than the positive roton signal created by the beams, and presence of both positive and negative roton signals together. It is natural that the negative roton creation by the beams requires the ⁴He-atom energies ~12 K, while the positive roton creation by the atomic beams requires energies ~35 K. Therefore, successive increase in the heater power resulting in an increase in the ⁴He-atom energies gives solid evidence that the negative rotons are first created in the liquid by the helium atomic beams.

4 illus, 1 table, 27 ref

020316   Vyas A D;Rana V A;Bhatnagar S P;Vashisht V M (Physics Dep, School of Sciences, Gujarat University, Ahmedabad, Email: ranava2001@yahoo.com) : Dielectric dispersion and relaxation of mixtures of 1-propanol and phenol at lower microwave frequencies. Indian J pure appl Phys 2008, 46(7), 521-5.

Complex permittivity of 1-propanol, phenol and mixtures of 1-propanol + phenol over wide range of concentration are measured over the frequency range 30MHz to 3.0 GHz using Vector Network Analyzer (VNA). Open ended co-axial probe technique suggested by Wei and Sridhar [Rev Sci Instr, 60 (9) (1989) 304] is used to obtain dielectric constant. The measured values of ∈' and ∈" are fitted to Debye equation to obtain dielectric parameters. Obtained values of relaxation time of liquid mixtures are plotted against the concentration of one of the components of the liquid mixtures. Non-linear variation of relaxation time with concentration has been interpreted in terms of molecular interaction among the molecular species of different kinds in liquid mixtures.

020315   Vijay Kumar;Vats R P;Goyal S;Sandeep Kumar; Pathak P P (Physics Dep, Sushila Devi Bansal College of Technology, Indore-452 012, Email: vijay_phd05@rediffmail.com) : Interaction of electromagnetic radiation with human body. Indian J Radio Space Phys 2008, 37(2), 131-4.

Whole body specific absorption rate (SAR) is calculated for different frequencies as a function of distance from transmission tower. Comparing with safe limits of exposure as standardized by different international agencies, safe distance of residence from transmission tower is determined. The SAR for fat at a distance of 10, 20, 30, 40, 50 and 60 m is found to be harmful for 27.12-10000 MHz, above 100, 1500, 5000, 8000 and 10,000 MHz, respectively. Harmful range for cortical bone, spongy bone and skeletal muscle is also calculated.

020314   Verma S K;Rajput S S (Physics Dep, Bundelkhand University, Jhansi-248 128) : Electronic structure of chromium-aluminium alloys. Indian J pure appl Phys 2008, 46(3), 204-8.

Electronic structure of Cr-Al alloys has been studied by using the charge self-consistent Korringa-Kohn-Rostoker Coherent Potential Approximation method. Results for density of states are presented and found to be in very good agreement with reflected X-ray photo spectra results. It has been found that half width of density of states band of these alloys increases approximately 5 per cent at 85 atomic percentage of Cr with respect to 95 and 75 percentage of Cr, which explains the change in shape and half width of experimental X-ray photo spectra results.

020313   Venkatram Reddy B;Ramana Rao G (University P G College, Kakatiya University, Godavarikhani-505 209) : Vibrational spectra and modified valence force field for N,N'-methylenebisacrylamide. Indian J pure appl Phys 2008, 46(9), 611-6.

Raman and Fourier transform infrared (FTIR) spectra of N,N'-methylenebisacrylamide have been recorded. A 35-parameter modified valance force field has been evaluated using 38-in-plane vibrational frequencies of the molecule. Unambiguous vibrational assignments have been made using eigenvectors and potential energy distributions computed in the process.

020312   Vaidyanathan G;Sekar R;Hemalatha R (Physics Dep, Pondicherry Engineering College, Puducherry-605 014, Email: hemalatha53@yahoo.co.in) : Effect of horizontal thermal gradient on ferroconvection. Indian J pure appl Phys 2008, 46(7), 477-83.

The effect of horizontal thermal gradient on ferro convective instability of a single component system subjected to two dimensional magnetic field has been studied. The fluid layer is assumed to be bounded by free boundaries. The exact solution of constitutive equation is derived using linear theory. Wide range of values of the ratio of horizontal and vertical temperature gradient have been considered. Normally, the magnetization parameter M₁ is very large and is taken to be 1000. The system is found to stabilize through stationary mode only. It has also been seen that the oscillatory instability is not possible.

020311   Tyagi S K;Wang S;Park S R (NO, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong) : Performance criteria on different pressure ratios of an irreversible modified complex Brayton cycle. Indian J pure appl Phys 2008, 46(8), 565-74.

The irreversible cycle model of a regenerative modified complex Brayton cycle has been established for the finite heat capacities of external reservoirs. The power output and efficiency have been optimized with respect to the cycle temperatures and the optimum performance parameters are calculated for a typical set of operating condition. It is found that there are optimal values of the intercooling, reheat and cycle pressure ratios at which the cycle attains the maximum performance. The optimal performance parameters are also found to be increasing function of the effectiveness of different heat exchangers, components efficiency and the heat capacitance rates of the external fluids, while it is found to be reversed in the case of the working fluid heat capacitance rate. The optimum operating parameters, the intercooling, reheat and cycle pressure ratios etc corresponding to the different performance parameters are obtained and discussed in detail. The results obtained are general and some of the important conclusions in the relevant references can be obtained directly from this paper.

020310   Thakur A;Ahluwalia P K (Physics Dep, Himachal Pradesh Univ, Shimla-171 005, Email: anil_t2001@yahoo.com) : Interionic pair potentials and partial structure factors of compound-forming quaternary NaSn liquid alloy: first principle approach. Pramana J Phys 2007, 69(4), 589-602.

Formulae for partial structure factors have been used to study partial structure factors of compound-forming quaternary liquid alloys by considering Hoshino's m-component hard-sphere mixture, which is based on Percus-Yevic equation of Hiroike. Formulae are applied to NaSn (Na, Sn, NaSn, Na₃Sn) which is considered as a quaternary liquid mixture with the formation of two compounds simultaneously. We have compared the total structure factors for ternary and quaternary alloys with experimental total structure factors which are found to be in good agreement. This suggests that, for suitable stoichiometric composition, two compounds are formed simultaneously. The hard-sphere diameters needed have been calculated using Troullier and Martins ab-initio pseudopotentials.

6 illus, 1 table, 29 ref

020309   Thakor P B;Patel V N;Thakor B Y;Gajjar P N; Jani A R (Physics Dep, Veer Narmad South Gujarat University, Udhna Magdalla Road, Surat-395 007, Email: pbthakor@rediffmail.com) : Bulk modulus of some simple liquid metals. Indian J pure appl Phys 2008, 46(6), 431-4.

The Bulk modulus B_T of some simple liquid metals viz: Li, Na, K, Rb, Cs, Mg, Zn, Cd, Al, In, Tl and Pb have been investigated on the basis of the long wavelength limit of the structure factor of one component plasma (OCP) reference system. To describe the electron-ion interaction our well established model potential is used alongwith Sarkar et al. Mod Phys Lett, B12(1998) 639, dielectric function. Good agreements between present results and experimental data have been achieved for monovalent liquid metals than the polyvalent liquid metals. A comparison of present results with experiments establishes the success of present form of local pseudopotential and the OCP reference system in the investigation of the Bulk modulus B_T of some simple liquid metals.

020308   Tewari S P;Sood J;Dhingra G;Silotia P (Physics and Astrophysics Dep, University of Delhi, Delhi-110 007, Email: sptewari@physics.du.ac.in) : Wave-vector and frequency dependent complex dielectric function and related physical properties of a weakly coupled one dimensional two component hot plasma. Indian J pure appl Phys 2008, 46(9), 637-45.

The complex dielectric function has been obtained for one dimensional two component weakly coupled classical and quantum hot plasmas in the entire wave-vector and frequency range. The related physical properties: dynamical structure factor and its singularities which yield collective modes, reflectivity of low energy photons and static pair correlation function about an impurity, positron, introduced in the plasma, have been computed and compared with the corresponding quantities in one component plasma. The results for the two plasmas are found to be markedly different.

020307   Tan A;Zhang T X;Wu S T (Physics Dep, Alabama A & M University, Normal, Alabama 35762, USA) : Pressure and density of air in mines. Indian J Radio Space Phys 2008, 37(1), 64-7.

Mines are the deepest cavities in the Earth's crust, where man has set foot and worked. The observed temperature gradients within the mines range from 10 to 50 K/km. The pressure and density of air inside mines are calculated by integrating the governing equation for the number density obtained from the hydrostatic equation and the perfect gas laws. The variation of the acceleration of gravity with depth is seen to have only minimal effects on the pressure and air density. The higher temperature gradients inside the mines are found to depress both the pressure and density of air there. Whereas the pressure must necessarily increase with depth due to the hydrostatic equation, the density of air can increase, remain constant, or actually decrease with depth, for temperature gradients of less than, equal to, or greater than 34 K/km, respectively. Air conditions in the deepest mine in the world are discussed.

020306   Tafreshia M J;Fazlib M (Physics Dep, Faculty of Science, Semnan University, Semnan, Iran, Email: m_jtafreshi@yahoo.com ) : Growth of ZnSe single crystals by CVT technique and study micromorphology. Indian J pure appl Phys 2008, 46(9), 646-50.

The vapour phase chemical transport in a closed tube has been investigated for a ZnSe-I₂ system. Based on a proposed thermodynamic model, the optimum condition for the growth of ZnSe single crystals is determined. A good agreement has been observed between the predicted optimum growth parameters and the experimental results. ZnSe single crystals are grown at different temperatures including optimum temperature for 2.5 mg/cm³ of iodine concentration. ZnSe single crystals grown at optimum temperature show better structural and morphological properties as compared to other temperature range.

020305   Suthan Kissinger N J;Jayachandran M;Perumal K;Sanjeevi Raja C (NO, Nesamony Memorial Christian College, Marthandam-629 165, Email: suthan.kissinger@gmail.com) : Structural and optical properties of electron beam evaporated CdSe thin films. Bull Mater Sci 2007, 30(6), 547-51.

Thin films of cadmium selenide (CdSe) as a semiconductor is well suited for opto-electronic applications such as photo detection or solar energy conversion, due to its optical and electrical properties, as well as its good chemical and mechanical stability. In order to explore the possibility of using this in optoelectronics, a preliminary and thorough study of optical and structural properties of the host material is an important step. Based on the above view, the structural and optical properties of CdSe films have been studied thoroughly in the present work. The host material, CdSe film, has been prepared by the physical vapour deposition method of electron beam evaporation (PVD: EBE) technique under a pressure of 5 x 10^-5 mbar. The structural properties have been studied by XRD technique. The hexagonal structure with a preferred orientation along the (0 0 2) direction of films has been confirmed by the X-ray diffraction analysis. The films have been analysed for optical band gap and absorbed a direct intrinsic band gap of 1.92 eV.

7 illus, 2 tables, 19 ref

020304   Subedi D P;Madhup D K;Adhikari K;Joshi U M (Physics Dep, Kathmandu University, Dhulikhel, Nepal) : Plasma treatment at low pressure for the enhancement of wettability of polycarbonate. Indian J pure appl Phys 2008, 46(8), 540-4.

The dc glow discharge plasma at low pressure was used for the treatment of polycarbonate surface to investigate the improvement in wettability. The effect of treatment time, applied power and sample- electrode distance on wettability and etching was studied. The surface energy of the sample was found to increase from 29.73 to 64.69 mJ/m² with 40s of treatment time. The results showed that wettability and etching of the sample depend strongly on treatment time, applied power and distance from the electrode. The relation for the wettability of the sample as a function of the sample-electrode distance has been found. It was found that dc glow discharge produced at a low pressure air can effectively etch a polycarbonate sample at the rate in the order of 10^-9 g/cm²/s. The stability of the modified surface by measuring the contact angle at different storage time has been investigated.

020303   Srivastava V;Sanyal S P;Rajagopalan M (Physics Dep, Barkatullah University, Bhopal-462 026, Email: vips73@yahoo.com) : First principles study of pressure induced magnetic transition in CrO₂. Indian J pure appl Phys 2008, 46(6), 397-9.

Using first principles density functional theory calculations based on the tight-binding linear muffin tin orbital method, the magnetic and electronic structures for the ferromagnetic state of CrO₂ at high pressure have been investigated. A pressure-induced second order magnetic phase transition from ferromagnetic (FM) to non-magnetic (NM) at very high pressure of 65 GPa is predicted. The ground state properties like magnetic moment and lattice parameter are in good agreement with the experimental results. The band structure and density of states are plotted for FM and NM states. In NM calculation at ambient conditions CrO₂ shows metallic phase, while it shows half-metallic phase in FM state.

020302   Srivastava S C L;Rao S V L S;Singh P (Nuclear Physics Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: shashi_uv@yahoo.com) : Development of 2D particle-in-cell code to simulate high current, low energy beam in a beam transport system. Pramana J Phys 2007, 69(4), 551-66.

A code for 2D space-charge dominated beam dynamics study in beam transport lines is developed. The code is used for particle-in-cell (PIC) simulation of z-uniform beam in a channel containing solenoids and drift space. It can also simulate a transport line where quadrupoles are used for focusing the beam. Numerical techniques as well as the results of beam dynamics studies are presented in the paper.

7 illus, 3 tables, 11 ref

020301   Srivastava R K;Prakash S G (Electronics & Communication Dep, University of Allahabad, Allahabad-211 002, Email: rks3e@rediffmail.com) : Photoelectret study of Sm doped ZnO and ZnO-Pb₃O₄ mixed lattice. Indian J pure appl Phys 2008, 46(4), 266-9.

Photoelectret characteristics of rare earth ion Sm doped ZnO and ZnO-Pb₃O₄ along with pure ZnO have been studied. The dependence of photoelectret charge on excitation field, photo polarization time, dark depolarization time, intensity and wavelength of illumination have been evaluated. With increase in polarization time, decrease in depolarization time and increase in intensity of illumination, photoelectret charge continues to increase. With increase in field, photoelectret charge first increases and later tends to saturation. No photoelectret effect was observed in nano structured ZnO.

020300   Srivastava A K;Gupta B R K (Physics Dep, Lovely Professional University, Phagwara-144 401, Email: srivastava_phy@yahoo co in) : Temperature dependence of thermal expansivity and volume thermal expansion of fullerenes. Indian J pure appl Phys 2008, 46(6), 406-9.

In recent years, there has been intense activity, both experimental and theoretical, in exploring fascinating physical properties of newer form of carbon, namely fullerenes. Fullerenes are currently being widely investigated since they show the anomalous properties of bulk modulus and specific heat of the materials as compared to the bulk material. A simple theoretical Equation of State model is used to analyze the temperature dependence of thermal expansion coefficient, relative volume change and isothermal bulk modulus of a fullerene C₆₀. A good agreement between our theoretically calculated results and available experimental data has been obtained.

020299   Srinivasan N;Rajamannan B;Ramesh K (Physics Dep, Annamalai Univ, Annamalai Nagar, Tamil Nadu) : Physical propetry investigation of albino rat testis treated with Sildenafil citrate (Viagra). Acta Cienc Indica-Chem 2007, 33(3), 319-21.

An attempt has been made to evaluate the physical properties using the standard procedures. This estimation has been made at room temperature by making use of structural and mechanical investigation. The results are discussed in term of testis variations due to drug administration.

1 table, 6 ref

020298   Sood D;Gurpal Singh;Tripathi C C;Sood S C; Joshi P (Electronics & Communication Dep, Ambala College of Engineering & Applied Research, (Near Mithapur), Ambala Cantt., Haryana, Email: deepaksood1980@yahoo.com) : Design, fabrication and characterization of microstrip square patch antenna array for X-band applications. Indian J pure appl Phys 2008, 46(8), 593-7.

Microstrip patch antenna array to be used for X-band short-range microwave applications has been introduced. This antenna maintains a maximum gain of 14.6 dB for far field region w.r.t paraboloidal rectangular aperture antenna. It is actually a probe (coaxial) fed antenna with quarter wave sections that are fabricated as an arrangement for impedance matching with Ω coaxial cable. This antenna works well in the frequency range 8.45-9.33 GHz with a maximum at 8.53 GHz. It is basically a low cost, lightweight, medium gain and narrowband antenna and suited for short-range microwave applications such as a feeding element for other antennas and in research institutes as a reference antenna. It can also be used at the output of signal conditioning circuit for receiving signals from micro electromechanical sensors.

020297   Sirdeshmukh D B;Sirdeshmukh L;Subhadra K G (Physics Dep, Kakatiya Univ, Warangal-506 009, Email: dsirdeshmukh@yahoo.com) : Fifty years of Szigeti's dielectric theory. Pramana J Phys 2007, 69(4), 491-520.

During the period 1949-1961 Szigeti published four seminal papers on the dielectric behaviour of crystals. Szigeti's theory is applicable to isotropic and anisotropic, ionic and covalent crystals with different structures. Szigeti's theory connects dielectric, spectroscopic and elastic properties. An important outcome of Szigeti's theory is the concept of the effective ionic charge (s). It is pointed out that s correlates with a number of physical properties and is a measure of ionicity of the interatomic bond. Since Szigeti's work, several theoretical models have been proposed to account for the fact that s <60> 1. These models provide an insight into the complex polarization mechanisms in solids. This review summarizes Szigeti's work and the work that followed; the implications and applications of Szigeti's theory are discussed. Some new results are also included.

13 illus, 11 tables, 83 ref

020296   Singhal S;Saxena A K;Dasgupta S (Solid State Devices and VLSI Technology Group, Department of Electronics and Computer Engineering, Indian Institute of Technology Roorkee, Roorkee-247 667, Email: kumarfec@iitr.ernet.in) : Estimation of various scattering parameters and 2-DEG mobilities from electron mobility calculations in the three conduction bands Γ, L and X of gallium arsenide. Pramana J Phys 2007, 69(4), 687-92.

The electron drift mobility in Γ conduction band of GaAs has been calculated before, but for the first time, we have made attempts to estimate the electron mobilities in higher energy L and X minima. We have also calculated the value of mobility of two-dimensional electron gas needed to predict hetero-structure device characteristics using GaAs. Best scattering parameters have been derived by close comparison between experimental and theoretical mobilities. Room temperature electron mobilities in Γ L and X valleys are found to be nearly 9094, 945 and 247 cm²/V-s respectively. For the above valleys, the electron masses, deformation potentials and polar phonon temperatures have been determined to be (0.067, 0.22, 0.39m₀), (8.5, 9.5, 6.5 eV), and (416, 382, 542 K) as best values, respectively. The 2-DEG electron mobility in Γ minimum increases to 1.54 x 10⁶ from 1.59 x 10⁵ cm²/V-s (for impurity concentration of 10¹⁴ cm^-3) at 10 K. Similarly, the 2-DEG electron mobility values in L and X minima are estimated to be 2.28 x 10⁵ and 1.44 x 10⁵ cm²/V-s at 10 K, which are about <126>4.5 and <126>3.9 times higher than normal value with impurity scattering present.

16 ref

020295   Singh M;Vijay Y K;Sharma B K (Physics Dep, Rajasthan Univ, Jaipur-302 004, Email: mangej_singh@yahoo.com) : Variable electron beam and its irradiation effect on optical and electrical properties of CdS thin films. Pramana J Phys 2007, 69(4), 631-8.

Low energy electron accelerator has been constructed and tested. The electron beam can operate in low energy mode (100 eV to 10 keV) having a beam diameter of 8-10 mm. Thin films of CdS having thickness of 100 nm deposited on ITO-coated glass substrate by thermal evaporation method have been irradiated by electron beam in the above instrument. The I-V characteristic is found to be nonlinear before electron irradiation and linear after electron irradiation. The TEP measurement confirms the n-type nature of the material. The TEP and I-V measurements also confirm the modification of ITO/CdS interface with electron irradiation.

5 illus, 22 ref

020294   Singh K;Bahadur D (School of Physics and Materials Science, Thapar University, Patiala-147 001, Email: kusingh@tiet.ac.in ) : Stability and phase transition in Al₆₅Cu₂₀Co_15-xFex (0≤x≤15)quasi-crystalline systems. Indian J pure appl Phys 2008, 46(7), 497-501.

The samples Al₆₅Cu₂₀Co_15-xFex (0≤x≤15), Al₆₃Cu₂₅Fe₁₂ and Al₆₀Cu₂₀Fe₁₅Si₅ have been synthesized. Their stability and formed phases are investigated using differential thermal analysis (DTA) and X-ray diffraction (XRD), respectively. The maximum stability in alloys is found when the Fermi wave vector, k_F satisfies the relation K_P = 2k_F. Apart from this, specific range of e/a (electron per atom) and atomic size ratio of constituents also play an important role in forming the thermodynamically stable quasicrystals.

020293   Singh B P;Tripti S;Singh V (Physics Dep, Institute of Basic Sciences, Khandari, Agra-282 002, Email: drbps.ibs@gmail.com) : Analysis of optoelectronic properties of A<. Indian J pure appl Phys 2008, 46(7), 502-6.

The dependence of refractive index for I-VII, II-VI, III-V semiconductors including alkali halides on the energy band gap and the optical electronegativity difference has been studied. The relationships have been established for estimating the refractive index of materials. In addition, an interrelation between the energy band gap, polarizability and magnetic susceptibility has also been investigated. The computed values of the parameters are then compared with the literature values.

020292   Sinaha K;Mohana R;Shelkea V;Gaura N K;Singh R K (Superconductivity Research Lab, Physics Dep, Barkatullah University, Bhopal-462 026, Email: kiranpatyal@rediffmail.com) : Superconductivity in Mg_1-xM_xB₂ (M = Cu and Ag) system. Indian J pure appl Phys 2008, 46(6), 420-2.

The polycrystalline samples with nominal compositions Mg_1-xM_xB₂ (M = Cu, Ag; x = 0, 0.05) have been synthesized through solid-state reaction method. All the samples were synthesized from the stoichiometric mixtures of Mg, B, Cu and Ag. The samples were sintered at 850°C for 2 h in the presence of high purity argon flow. The X-ray diffraction (XRD), R-T measurement and scanning electron microscopy (SEM) techniques have been used for the characterization of samples for phase formation, superconducting transition temperature (T_c) and microstructure, respectively. It is noticed from the XRD patterns that the Cu and Ag doping leads to the formation of Mg-Cu and Mg-Ag alloys as the secondary phase, respectively along with the major phase of MgB₂. In case of Cu doping T_c decreases slightly and Ag doping has no effect on it. The grain size remains the same with these dopings, but the grain connectivity improves.

020291   Shukla R K;Atul Kumar;Mishra M;Dwivedi P (Chemistry Dep, BND College, Kanpur) : Comparative study of two liquid models in the prediction of excess thermodynamic properties of liquid ternary systems. Indian J pure appl Phys 2008, 46(9), 629-36.

Excess thermodynamic properties i.e. excess volume, excess molar enthalpy, excess molar entropy, excess free energy and excess heat capacity have been evaluated using Prigogine-Flory-Patterson (PFP) and Bertrand-Acree-Bruchfield (BAB) theory for three ternary and its contributory binary liquid systems namely (1) tolune- cyclohexane- carbon tetrachloride and its contributory binaries (toluene+ cyclohexane), (cyclohexane + carbon tetrachloride), (carbon tetrachloride + toluene); (2) benzene - cyclohexane- toluene and its contributory binaries, (benzene + cyclohexane), (cyclohexane + toluene), (toluene + benzene); (3) carbon tetrachloride- cyclohexane - benzene and its contributory binaries, (carbon tetrachloride + cyclohexane), (cyclohexane + benzene) and (benzene + carbon tetrachloride) at 298.15 K over a wide range of compositions. The results so obtained from these two theories are very much comparable and are in good agreement.

020290   Shukla P;Tiwari R K;Tanwar A;Singh S P (NO, Hindustan College of Science and Technology, Farah, Mathura (U P), Email: mulayamgaur@rediffmail.com) : New approach for the measurement of glass transition temperature of polymer. Indian J pure appl Phys 2008, 46(8), 535-9.

Global thermally stimulated discharge current (TSDC) and partial thermally stimulated discharge current (PTSDC) spectra were recorded to investigate the molecular motions at glass transition temperature (T_g) level in both sided vacuum aluminized 30 μm thick poly (methyl methacrylate) samples. The calculated values of charge released, relaxation time and activation energy correspond to α and β relaxation processes. The TSDC peak occurred at a temperature, which is close to T_g of the polymer. This temperature is in agreement with the T_g determined using DSC technique.

020289   Shelar R N;Savale V S;Borse R Y;Hasan M; Sawant A B (Physics Dep, Arts, Science & Commerce College, Dist Nashik, Maharashtra-423 204, Email: absawant@rediffmail.com) : Excess volumes and deviation in viscosities of binary mixtures of o-dichlorobenzene and o-chlorophenol with di-isopropyl ether, 1.4-dioxan, diphenyl ether and t-butylmethyl ether. Indian J pure appl Phys 2008, 46(8), 552-60.

The densities and viscosities of binary mixture of o-dichlorobenzene and o-chlorophenol with d-isopropyl ether, 1.4-dioxan, diphenyl ether and t-butyl methyl ether have been measured at atmospheric pressure and in the temperature range 303-313K at the interval of 5K. The data have been utilized to compute the excess volumes and deviation in viscosities. The results have been interpreted in terms of molecular interactions existing between the components of the mixtures.

020288   Sharma Y K;Surana S S L;Singh R K (Physics Dep, Govt. Post Graduate College, Rudrapur-263 153) : Optical absorption and fluorescence spectra of Pr (III) doped borosilicate glasses and their Judd-Ofelt analysis to study lasing characteristics. Indian J pure appl Phys 2008, 46(4), 239-44.

Optical absorption and fluorescence spectra of Pr³⁺ doped borosilicate glasses of the composition (in wt.%) 68.94 SiO₂-22.55 Na₂O-1.91 CaO-4.96 K₂O -0.85 B₂O₃-0.29 As₂O₃-χPr₆O₁₁ where χ = 0.0, 0.2, 0.3 and 0.5 have been studied in UV-VIS/NIR regions. Judd-Ofelt theory has been applied to the f ↔ f transitions for evaluating variousΩ_λ (λ= 2, 4, 6) parameters. Using the fluorescence data and these Ω_λ parameters, various radiative properties like spontaneous emission probability, branching ratio, radiative lifetime and stimulated emission cross-section of various emission lines have been evaluated. The values of these parameters have been used to predict potential laser transitions. The bonding environment surrounding the rare earth ion in this glass-network has also been discussed.

020287   Sharma V;Thakur N;Sharma D R;Rangra V S;Negi N S (Physics Dep, H P University, Shimla-171 005, Email: ntb668@yahoo.co.in) : Dielectric relaxation studies of binary mixtures of ethyl alcohol and N,N-dimethylacetamide in the benzene solution from microwave absorption data. Indian J pure appl Phys 2008, 46(3), 212-4.

Dielectric relaxation studies of different molar concentrations of ethanol in the binary mixtures of ethanol and N, N-dimethylacetamide in benzene solutions have been studied at 9.883 GHz by using standard standing microwave techniques and Gopala Krishna's [Trans Faraday Soc, 33 (1957) 767] single frequency concentration variation method at different temperatures (25, 30, 35 and 40°C). It is found that dielectric relaxation time varies non-linearly with the variation in molar concentration of ethanol in the whole concentration range of the binary mixture. The solute-solute and solute-solvent types of molecular associations have been proposed. The energy parameters (ΔH_ε, ΔF_ε, ΔS_ε) for the dielectric relaxation process of binary mixtures containing 50% molar concentration of ethanol have been calculated at the respective given temperatures. Comparison has been made with the corresponding energy parameters for viscous flow process. It is found that the dielectric relaxation process can be treated as the rate process like the viscous flow process.

020286   Sharma S K;Bothra C;Sharma G D (Physics Dep, J N V University, Jodhpur-342 005) : Role of binding energy in the generation of photocurrent in bulk heterojunction organic materials. Indian J pure appl Phys 2008, 46(8), 588-92.

The role of binding energy of electron hole pair in the generation of photocurrent has been studied using Braun's model based on Onsager theory. For the study, two bulk heterojunction devices namely poly (2-methoxy-5-(3',7'- dimethyloctyloxy)-p-phenylene vinylene)(OC₁C₁₀-PPV) and poly (2-methoxy-5-(3', 7'-dimethyloctyloxy)-1-4-phenylene vinylene) (MDMO-PPV) have been chosen. These materials act as electron donor in the bulk hetero-junctions and are based on intermixing of conjugate polymers and fullerene derivatives. Photocurrent has been calculated theoretically for different values of exciton binding energies. The variation of photocurrent with binding energy shows that a constant value of photocurrent is obtained up to a threshold value of 0.6 eV. When binding energy exceeds the threshold value, photocurrent diminishes rapidly. Thus, binding energy plays an important role in the generation of photocurrent and can be used as a primary parameter for the characterization of organic semiconductors in solar cell applications.

020285   Sharma N;Singh S P;Kumar S (Physics Dep, Christ Church College, Kanpur-208 001) : Composition dependence of density of states in a-Se_100-xSn_x thin films. Pramana J Phys 2007, 69(4), 681-6.

Reports the DC conductivity measurements at high electric fields in vacuum evaporated amorphous thin films of a-Se₁₀₀-xSn_x (x = 0, 2, 4, 6) glassy alloys. Current-voltage (I-V) characteristics have been measured at various fixed temperatures. In these samples, at low electric fields, ohmic behaviour is observed. However, at high electric fields (E ~ 10⁴ V/cm), non-ohmic behaviour is observed. An analysis of the experimental data confirms the presence of space charge limited conduction (SCLC) in the glassy materials studied in the present case. From the fitting of the data to the theory of SCLC, the density of defect states (DOS) near Fermi level is calculated. Increase in DOS with increase in Sn concentration has been found which could be correlated with the electronegativity difference between the two elements used here in making the glassy alloys. The peculiar role of the element Sn as an impurity in the pure Se glassy alloy is also discussed.

6 illus, 1 table, 24 ref

020284   Sharma M P;Jain S K;Krishnamurthy A; Srivastava B K (Physics Dep, University of Rajasthan, Jaipur-302 004, Email: mps_45@yahoo.com) : Synthesis and characterization of sodium substituted lanthanum manganite. Indian J pure appl Phys 2008, 46(5), 325-9.

Three compositions of sodium substituted lanthanum manganites La_1-xNa_xMnO₃ (for x = 0.1, 0.2 and 0.5) have been prepared using sol-gel technique followed by two different thermal treatments. Attempts to prepare 50 atomic per cent Na (for La) substituted sample, which would be the maximum permissible amount of Na as per valence consideration, did not yield a compound of correct stoichiometry. Of the two stoichiometric samples, the one with 20 atomic% sodium shows an ordered ferromagnetic state and that with 10 atomic% sodium is disordered ferromagnet.

020283   Sharma M K;Saikia B K (NO, Centre of Plasma Physics, Tepesia, Sonapur, Guwahati, Assam-782 402) : Discharge conditions and emission spectroscopy of N₂ and N2<. Indian J pure appl Phys 2008, 46(7), 463-70.

The variations of stainless steel cathode temperature (T_c) as a function of nominal plasma power (driven by discharge frequency) and duty cycle at different pressures (0.6-3.2 torr) in nitrogen plasma are reported in conditions favourable for plasma nitriding. Above power at 200 kHz, it is found that increase in power does not have any significant effect on T_c. Corresponding optical emission spectroscopy (OES) study near the cathode surface shows that the presence of vibrational bands of second positive system of N₂ (Δv = 0, -1, -2, -3) and first negative system of N²⁺ (Δv = 0, -1, -2) are dominant. The variation of intensity of those nitrogen molecular bands as a function of discharge power at various pressures has been studied. At 2 torr, the vibrational temperature of N₂ molecule is calculated from N₂ vibrational spectra at different discharge power regime as frequency is varied from 100 to 500 kHz. The variation of power in this frequency range 50-500 kHz has a similar effect on T_c and optical emission intensity. Floating potential in variable power conditions has been measured by Langmuir probe which shows a plateau after 3.2 Watt/cmM^>2 (at 200 kHz) plasma power density.

020282   Shanker Rao T L;Dhurandhar H D;Lad K N;Arun Pratap (Condensed Matter Physics Lab, Applied Physics Dep, Faculty of Technolo, M S University of Baroda, Vadodara-390 001, , Email: apratapmsu@yahoo.com) : Kinetic analysis of crystallization processes in amorphous 2826A (Ni₃₆Fe₃₂Cr₁₄P₁₂ B₆) metallic glass. Indian J pure appl Phys 2008, 46(6), 390-3.

The crystallization processes of 2826A (Ni₃₆Fe₃₂Cr₁₄P₁₂ B₆) metallic glass were investigated using differential scanning calorimetry (DSC) at various heating rates. The thermograms at all scanning rates show two exothermic events. Different methods of kinetic analysis were employed at non-isothermal condition to derive important kinetic parameters namely activation energy of crystallization (E), frequency factor (A) and Avrami exponent (n) for the two exothermic peaks. The obtained values of E for peaks 1 and 2 are 298 and 457 (kJ/mol), respectively. The obtained Avrami exponent values 2.2(peak1) and 1.6(peak2) indicate one-dimensional and surface crystallization, respectively.

020281   Shaktawat V;Jain N;Dixit M;Saxena N S;Sharma K;Sharma T P (Semiconductor and Polymer Science Lab, Physics Dep, University of Rajasthan, Jaipur-302 004, Email: n_s_saxena@rediffmail.com ) : Temperature dependence of conductivity of polypyrrole doped with sulphuric acid. Indian J pure appl Phys 2008, 46(6), 427-30.

Polypyrrole samples doped with sulfuric acid have been synthesized by using chemical oxidative polymerisation technique in different ways. The monomer mixed with acid (sample S₁) and oxidant mixed with acid (sample S₂) is characterized by XRD and FTIR spectroscopy. Electrical conduction in these doped samples are studied through the I-V measurements at room temperature as well as function of temperature from 313 to 473 K. The I-V lharacteristics for both the samples have been found to be linear but conductivity of sample S₂ is found to be higher. Temperature dependence of conductivity suggests a transition from semiconducting nature to metallic nature with increase in temperature. Activation energies for both the samples have been found to be in milli electron volt range, 96.76 meV and 116.72 meV for samples S₁ and S₂, respectively.

020280   Shah S;Singh D;Qureshi A;Singh N L;Singh K P; Shrinet V (Physics Dep, M S University of Baroda, Vadodara-390 002, Email: singhnl_msu@yahoo.com) : Dielectric properties and surface morphology of proton irradiated ferric oxalate dispersed PVC films. Indian J pure appl Phys 2008, 46(6), 439-42.

Different concentrations of organometallic compound (ferric oxalate) have been dispersed in polyvinyl chloride (PVC) films. PVC has been synthesized by solution polymerization technique. These films have been irradiated with 3 MeV protons at a fluence of 1x10¹³ ions/cm². The frequency response of dielectric behaviour has been studied both in pristine and irradiated samples using LCR meter in the frequency range100 Hz-10MHz. The results so obtained are explained using the universal law of dielectric behaviour (ε α f^n-1). The results are also explained on the basis of intra-cluster motion. It is observed that the log conductivity increases with increase in metal concentration and also with the fluence. The dielectric constant/loss shows frequency dependent behaviour. SEM studies show that the particle size of metal compound decreases upon irradiation.

020279   Shah N A;Quadri M;Iqbal S Z (Electronics and Instrumentation Technology Dep, University of Kashmir, Srinagar-190 006) : Realization of CDTA based current-mode universal filter. Indian J pure appl Phys 2008, 46(4), 283-5.

New current-mode (CM) filter capable of providing simultaneously lowpass (LP), bandpass (BP) and highpass (HP) responses has been presented. The realization of notch and allpass (AP) responses can be easily achieved without matching or rotation of components. The circuit employs a single current differencing transconductance amplifier (CDTA), two capacitors and one resistor. The circuit uses a minimum number of active and passive components and permits orthogonal tunability of pole frequency (ω_o) and bandwidth (ω_o/Q) alongwith enjoying low active and passive sensitivities. PSPICE simulation results are obtained.

020278   Shah N A;Iqbal S Z;Parveen N (Electronics and Instrumentation Technology Dep, University of Kashmir, Srinagar-190 006, Email: nassgr@yahoo.co.uk) : Log-domain low pass high pass first-order filter. Indian J pure appl Phys 2008, 46(9), 667-70.

New first-order log-domain filter topology implementing simultaneously low-pass (LP) and high-pass (HP) filter functions has been presented. The circuit employs log-domain cells, current sources and grounded capacitor. The circuit has simple architecture, wider dynamic range at low power supply and higher frequency operation as it is based on log-exponential relation of a transistor. The electronic tunability of the proposed filter and grounded capacitor make it suitable for construction in IC technology. The PSPICE simulations results are found to be in close conformity with the theoretical results.

020277   Shah A K;Gajjar P N (NO, Sheth R. A. Bhavan's Science College, Khanpur, Ahmedabad-380 001) : X-ray diffraction studies of tungsten substituted molybdenum disulphide. Indian J pure appl Phys 2008, 46(7), 488-90.

Transition metal dichalcogenide single crystals of tungsten substituted molybdenum disulphide have been grown by chemical vapour transport technique using iodine as transporting agent and direct vapour transport technique. The composition of grown crystals was confirmed on the basis of energy dispersive analysis of X-ray (EDAX) and remaining structural characterization was determined by X-ray diffraction (XRD). The growth condition, growth mechanism and lattice parameters are also determined and presented.