000097   Wahlstrand J K;Merlin R (Physics Dep, The University of Michigan, Ann Arbor, MI 48109-1120) : Impulsive stimulated Raman scattering by phonon polariton and the cherenkov effect. Indian J Phys-Pt B 2003, 77(1), 101-11.

Spatially resolved electro-optic sampling experiments on ZnTe and GaP demonstrate that the generation of coherent phonon polarotons by ultrafast optical pulses can be-described as Cherenkov radiation. Coherent phonon polaritons generated through impulsive stimulated Raman scattering are usually studied using the transient grating geometry, in which two ultrafast pulses define a specific polariton wavevector. Alternatively, polatriton generation using a tightly focused pump pulse is usually associated with the Cherenkov effect. How that the two methods, stimulated Raman scattering and the Cherenkov interpretation, are fundamentally the same and discuss the implications of this on the interpretation of transient grating experiments. Shows that the generation of THz radiation by non-resonant optical rectification can be described as Cherenkov emission by a spatially extended source. Experiments and calculations are presented for various excitation geometies.

10 illus, 1 tables, 44 ref

000096   Vyas P R (NO, Government Polytechnic, Chhotaudepur, Dist. Baroda, Gujarat-391 165) : Effect of pre-thermal treatments on thermoluminescence of synthetic qurtz. Indian J pure appl Phys 2003, 41(2), 128-30.

The effect of pre-thermal treatments on the thermoluminescene (TL) characteristics of synthetic quartz has been investigated. Various gamma dose exposure was given to the sample after thermal pre-treatment. The systematic variation in TL glow curves with different pre-thermal treatment is discernible. In a most significant observation it was found that, TL intensity enhanced abruptly, when the specimen was pre-heat treatedat 600° C. This observation is explained on the basis of phase transformation in synthetic quartz.

3 illus, 8 ref

000095   Vijayan K K;Kuriakose S;Nair K P R;Rasheed T M A (Laser and Spectroscopy Laboratory, Physics Dep, Cochin University of Science and Technology, Cochin-682 022) : CH overtone spectrum of t-butyl amine: a C<. Asian J Spectrosc 2002, 6(3), 125-31.

The results of an experimental study of CH and NH stretching vibrational overtone absorption spectrum of liquid state 1-butlyl amine in the infrared region 2000-700 nm are reported. The observed CH bands are analyzed on the basis of coupled local mode model with the assumption that methyl groups are independent. The analysis enables us to determine the dependence of the coupling between CH oscillators in a methyl manifold on factors such as overtone energy. It is found that the observed CH local mode overtone and local-local combination frequencies are well predicted by the eigen states of a C^3v coupled oscillator Hamiltonian.

4 illus, 22 ref

000094   Vagins M R (Department of Physics and Astronomy, University of California, Irvine, 41 29 Reines Hall, CA 92697, USA) : Results from super-kamiokande and K2K. Pramana J Phys 2003, 60(2), 249-59.

Results from super-kamiokande-I's entire 1496 live days of solar neutrino data are presented, including the absolute flux, energy spectrum, zenith angle (day/night) and seasonal variation. The possibility of MSW and vaccum oscillations is discussed in light of these results. Results from the first 1289 days of super-K-I's atmospheric neutrino analysis are also presented, including the evidence for vμ → vτ oscillations, against vμ → v_sterile oscillations, and the current limits on proton decay. Finally, results based on 5.6 x 10¹⁹ protons on target are given for the K2K long-baseline neutrino oscillation experiment.

9 illus, 19 ref

000093   Tripathi G S (Physics Dep, Berhampur University, Berhampur-760 007, Orissa) : Some recent aspects of IV-VI based diluted magnetic semiconductor. Indian J Phys-Pt A 2003, 77(2), 99-102.

Presents a brief review of the progress made in semiconductor physics and devices in the last century. A concise historical sketch of research in IV-VI semiconductors is also presented. Some novel features of diluted magnetic semiconductors (dms) based on IV-VI systems are highlighted. Finally, recent results obtained by the authors's group are discussed.

41 ref

000092   Tantawi R S (Department of Mathematics, Faculty of Science, Zagazig University, Zagazig, Egypt) : Scattering of protons and antiprotons by hydrogen-like atoms. Indian J pure appl Phys 2003, 41(2), 100-4.

The impact parameter method is applied to the excitation of hydrogen-like atoms in the 2s-state. Cross-sections for the n<61>3 excitation of H(2s) atoms and H⁺(2s), Li⁺(2s) ions, by colliding with protons (p) and antiprotons(p) are evaluated for incident energies, ranging from 1.5 KeV to 2500 KeV. The results of calculations for hydrogen atoms are compared with a previous work.

2 illus, 25 ref

000091   Srivastava K K P;Sinha K K;Banerji D;Ghose S (Department of Physics, T M Bhagalpur University, Bhagalpur-812 007) : Mossbauer, EPR and IR studies of some Fe doped dielectric materials. Indian J pure appl Phys 2003, 41(5), 393-7.

The PbTiO₃ and BaTiO₃ are well-known ferroelectrics of ABO₃ type perovskite structure with dielectric constants of about a few hundred. Several ceramics synthesised partially with other divalent, tetravalent and pentravalent atoms show high dielectric constants and are useful for electronic components and hence their characterisation is important. Mossbauer, EPR and IR methods can be quite effective provided these ceramics contain a small percentage of Fe which produces spectra depending upon its valence state and local symmetry. The spectra of such lead and strontium titanates show the presence of high spin Fe(III) valence state as dindicated by QS, IS and g-values. The IR band at around 600 cm^-1 seems to presence of high spin Fe(III) valence state as indicated by QS, IS and g-values. the IR band at around 600 cm ^{-1 seems to orginate from FeO₆} polyhedron besides the susual absorption band at around 410 cm^-1 coming from the TiO₆ polyhydron.

5 illus, 1 table, 11 ref

000090   Sliman L I;Farag B S;Zayed H A;Shehata F M (NO, University College for Art, Science & Education, Ein Shams University) : Optical properties of Sn Te_xSe_1-x thin films. Indian J pure appl Phys 2003, 41(2), 131-8.

Ternary alloys of SnTe_xSe_1-x (0±x±1) were synthesized by direct fusion method. The SnTe_xSe_1-x films were prepared by thermal evaporation under vacuum of about 10^-5 torr and with evaporation rate of about 30 nm/min. X-ray diffraction and microrobe analysis technique, investigated the structural and the composition analysis of SnTe_xSe_1-x in powderand thin film forms, respectively.X-ray diffraction patterns of the as-deposited and the annealed films of this system reveal that, these have polycrystalline nature of orthorhombic sturcture for alloys with compositiions x<61>0.6, 0.8 and 1. The variation of lattice parameters with different compositions x were also determined. The optical constants (the refractive index n, the absorption index k, the absorptin coefficient α, the dielectric constans ε₁ and ε₂) of SnTe_xSe_1-xfilms were determined for different thickness in the spectral range 500-2500 nm. The optical absorption results indicatethat, the fundamental absorption edge for SnTe_xSe_1-x (0±xε0.6) films is due to optical energy gaps for annealed films decreased as comapred with the as-depositied films. The decrease of the energy gaps is attributed to the change in the structureof the films from amorphous to crystalline. the variations of the optical constants (n, k, ε₁ and ε₂) with composition were investigated.

10 illus, 4 tables, 19 ref

000089   Singh S S (Physics Dep, , Motihari-845 401, Bihar, India) : Theory for equation of state of hard D-sphere fluid mixture. Indian J Phys-Pt A 2003, 77(2), 143-5.

The equation of state for a fluid mixture of hard D-sphere is discussed. There approach is based on the physical interpretation of the reciproval of activity. Using the physical interpretation of the reciprocal of activity, a n unified expression is derived for the equation of state of D-dimensional fluied mixture of hard D-spheres. The results for binary mixture of hard D-sphere are discussed.

1 illus, 1 tables, 4 ref

000088   Singh S K;Sushil Kumar;Gwal A K (Space Science Laboratory, Department of Physics & Electronics, , Bhopal-462 026) : Initial results of VLF emmisions observed on the ground station at Maitri, Antartica. Indian J Radio Space Phys 2003, 32(2), 70-4.

The ground based VLF database from Indian Antartic station Maitri (70°46′ S, 11°44′ E, L ″ 4.6) has been searched for very low frequency (VLF) emmisions during January-February of the years 1998 and 1999. The VLF recording system was successfully installed during the XVII Indian Scientific Expedition to Antartica (ISEA) 1997-98. The spetrograms of analysed data have revealed the common occurence of various emmision events like chorus rising emmisions, emmision of rising type, falling emmision of hook type and multiple emmisions. Also the observed emmisions (periodic and quasi-periodic) are found to be risers and fallers triggered from the top of hiss band.

5 illus, 13 ref

000087   Singh K;Sood N K (Department of Physics, Guru Nanak Dev University, Amritsar-143 005) : Viscosity and thermal conductivity of gas mistures. Indian J pure appl Phys 2003, 41(2), 121-7.

A method of proposed for estimating viscosity and thermal conductivity of gas mixtures from the pure component data. Deviations of the results predicted by the approximate relationships developed are of the same order, as the uncertainty in the experimental measurements.

5 tables, 31 ref

000086   Singh B K;Menon V J;Sood K C (Department of Physics, Banaras Hindu University, Varanasi-221 005) : Correction term, in total phonon conductivity. Indian J pure appl Phys 2003, 41(5), 354-7.

In Holland's two-mode thermal conductivity theory, the correction term K_c (which represents the effect of momentum conserving normal processes in the Callaway model) was treated under certain limitations. To be specific, (i) his starting expression of K_c had an unwarranted temperature-dependent coefficient, (ii) the Taylor expansion of integrated was not quite satisfactory, and (iii) use of the same functional form of the three phonon normal process relaxation rate at low and high frequencies was not justified. These deficiencies were overcome by starting with the correct expression of K_c doing a careful Taylor expansion and also incorporating the umklapp processes, apart from the normal ones. The relative importance of K_c is illustrated numerically for Si and LiF.

1 tables, 23 ref

000085   Sigl G (GReCO, Institut d' Astrophysique de Paris, CNRS, 98bis Boulevard Arago, 75014 Paris, France) : Probing physics at extreme energies with cosmic ultra-high energy radiation. Pramana J Phys 2003, 60(2), 279-89.

The highest energy cosmic rays observed possess macroscopic energies and their origin is likely to be associated with the most energetic processes in the universe. Their existence triggered a flurry of theoretical explanations ranging from conventional shock acceleration to particle physics beyond the standard model (SM) and processes taking place at the earliest moments of our universe. Furthermore, many new experimental activities promise a strong increase of statistics at the highest energies and a combination with γ-ray and neutrino astrophysics will put strong constraints on these theoritical models. Gives an overview over this quickly evolving research field with focus on testing new particle physics.

2 illus, 68 ref

000084   Sharma S L;Acharya H N (Departmentof Physics and Meteorology, Indian Insitute of Technology, Kharagpur-721 302) : Photoelectronic properties of HgI₂ crystals for nuclear radiation detection. Bull Mater Sci 2002, 25(2), 85-93.

Photoelectronic properties of red mercuric iodide single crystals, grown from its saturated solution in tetrahydrofuran, have been studied for the wavelength range 450-700 nm at temperatures 80, 110, 175, 235 and 300 K.Various aspects of the optical generation of charge carriers have been discussed. The computer simulation of the room temperature photoconductivity has generated the optimized values of the mobility-lifetime products (<109τ=5.67x10^-5cm²/V, μ_hτ_h=0.18x10<6>-5cm² /V), and surface recombination velocities (S_e=3.2x10<6>5cm/s, S_h=4.5x10<6>5cm/s) of the charge carriers in these crystals. The estimated values of the electron and hole drift lengths for typical electric fields suggest that, under the negative electrode illumination, THF α-HgI₂ crystals have high potential as regards to their use as photodetectors in most of the scintillation spectrometers.

8 illus, 2 tables, 22 ref

000083   Sharma H;Kiran Kumari;Singh L S;Choudhary RNP (University Department of Physics, Veer Kunwar Singh University, Arrah-802 301) : Synthesis structure and characterization of ceramic Ca₄Bi₂Ti₄Nb₆O₃₀. Bull Mater Sci 2002, 25(2), 133-6.

The polycrystalline samples of Ca₄Bi_{2Ti4Nb6O30 (herein designated CBTN) were synthesized by the conventional ceramic method. Preliminary X-ray structural study of the compound shwoed the formation of a single phase solid solution having orthorhombic structure in the paraelectric phase.Measurements of the dielectric constant (ε') and dielectric loss (tan δ) as a function of temperature (-180-200°C0 at 1 kHz and 10 kHz and also as a function of frequency (10²Hz to 10⁴Hz) at five different temperature [-180°C, -40°C, -10°C, 26°C (room temperature) and 75°C] have shown a dielectric anomaly and a phase transition at -13±1°C in CBTN.}

14 ref

000082   Sharma D K;Rai J;Israil M;Subrahmanyam P; Chopra P;Garg S C (Department of Physics, Indian Institute of Technology, Roorkee-247 667) : Effect of lightning on ionospheric temperature determined by SROSS-C2 satellite. Indian J Radio Space Phys 2003, 32(2), 93-7.

The ionospheric temperature in relation with the thunderstorm activity has been studied. The data were obtained by the RPA payload abroad Indian SROSS-C2 satellite, which has yielded valuable information on electron and ion temperatures (T_e and T_i) over low latitude locations in the altitude range 425-625 km. The data collected during solar minimum period from 1995 to 1996 have been analysed for anomalous variations in topside plasma temperature (electron and ion temperature). The data on thunderstorm have been obtained from IMD. The T_e is found to increase by 1.2-2.7 times during the thunderstorm activity when compared with the normal days, while T_i increases by about 1.2-2.4 times for the sameperiod. The enhancements in T_e and T_i have been attributed to the production of UHF-gamma radiations during a lightning sprite which propagates upward to the height of interest.

2 illus, 1 table, 18 ref

000081   Schmitt M;Siebert T;Kiefer W (NO, Institut for Physikalische Chemie der University Wurzburg, Am Hubland, D-97074 Wurzburg, Federal Republic of Germany) : Femtosecond time-resolved coherent Raman spectroscopy for probing molecular dynamics. Indian J Phys-Pt B 2003, 77(1), 49-62.

Reviews results on wavepacket dynamics investigated by means of femtosecond time-resolved four-wave-mixing (FWM) spectroscopy. First, it is shown that by making use of the various degrees of freedom which are offered by these nonlinear Raman or transient grating techniques information about molecular dynamics on different potential energy surfaces can be accessed and separated form each other. By varying the timing and wavelengths of the laser pulses as well as the wavelength of the detection window for hte FWM signal, different dynamics are coherentely excited nad probed by the nonlinear spectroscopy. As a model systme iodine in the gas phase was used. Second we report about selective excitation of the vibrational modes in the electronic ground state of porphyrin systems by means of a femtosecond time-resolved CARS (coherent anti-Stokes Raman scattering) scheme. By detecting the spectrum of the transient CARS signal, a detailed mapping of the dynamics initiated by the stimulated Raman pump proscess is achieved. The method is able to yield the dephasing behaviour and spectral information of the investigated system at the same time. The difference contributions to the ground state vibrational dynamics are selected by chaning the direction of the CARS signal analyzer in the polarization arrangement used.

11 illus, 57 ref

000080   Sarkar S K;Rajesh Kumar;Ahmed I;Prasad M V S N;Das J;De A K (Radio and Atmospheric Sciences Division, National Physical Laboratory, New Delhi-110 012) : Rain structure estimation from X-band radar reflectivity measurements for radio system applications in microwave and millimetre wave frequency bands. Indian J Radio Space Phys 2003, 32(2), 98-103.

The statistical morphology of radar reflectivity as a function of horizontal and vertical extension of rain is of considerable interest to those assessing the possible interference between terrestrial links and earth-space satellite links. In this paper, the horizontal and vertical extension of rain deduced from radar plan position indicator (PPI) and range height indicator (RHI) measurements have been presented. Such results of rain extension have also been deduced as a function of radar reflectivity factor (dBz). The radar reflectivity factor is the measure of the strength of the scattering cross-section of the rain cells. The scattering cross-section is responsible for causing interference to the radio signals. Probability distribution of radar reflectivity (dBz) deduced from both horizontal (PPI) and vertical extension (RHI) of rain cells has also been estimated.

7 illus, 10 ref

000079   Sarkar B C;Mandal M K (Radionics Laboratory, Physics Department, Burdwan University, Golapbag, Burdwan, (WB)-713 104) : Ring oscillator-based direct digital frequency synthesizer with improved spectral purity. Indian J pure appl Phys 2003, 41(5), 402-7.

Conventional direct digital frequency synthesizers (DDFS), designed using accumulators and phase registers, nrmally employ a clock signal of a fixed period. This results in synthesized signals haveing instantaneously varying time periods. The work employs a ring oscillator (RO) to provide the clock signal and the time period of the RO is properly varied to obtain fixed period, synthesized output signal. Experimental results are incorporated to prove the validity of the design modification algorithm.

6 illus, 5 ref

000078   Salem M A (Physics Department, Faculty of Science, Azhar University, Nars-City, Cairo, Egypt) : Studies on the opto-elecronic constants of alkali-halide crystals. Indian J pure appl Phys 2003, 41(5), 384-8.

Correlation between refractive index (n) of alkali-halide crystals and both energy band gap (E_g) and Pauling's electronegativity difference (ΔX) have been studied. The following relations are proposed for estimating the refractive index (n): n² +C=A/E_g^1/2 and n²+C=E/(ΔX)^0.425, where A, C and E are numerical constants. In addition, an interrelation between the energy band gap (E_g) and electronegativity difference (ΔX) has also been proposed. This relation reads as: E_g=4.45(ΔX)^0.85. The estimated values of the refractive index are utilized to evaluate the electronic polarizability of alkali-halides (α_e) by applying Lorentz-Lorentz formula. The computed values of refractive index, energy gap and electronic polarizability are compared with the literature ones.

3 illus, 4 tables, 21 ref

000077   Roy P (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Mechanisms of supersymmetry breaking in the minimal supersymmetric standard model. Pramana J Phys 2003, 60(2), 169-81.

Provides a bird's eyeview of current ideas on supersymmetry breaking mechanisms in the MSSM. The essentials of gauge, gravity, anomaly and gaugino/higgsino mediation mechanisms are covered briefly and the phenomenology of the associated models is touched upon. A few statement are also made on braneworld supersymmetry breaking.

5 illus, 2 tables, 16 ref

000076   Roshan La;Sharma N D (Physics Dep, Kurukshetra University, Kurukshetra-136 119) : Application of mossbaur spectroscopy to study the effect of fly-ash in agriculture soil. Indian J pure appl Phys 2003, 41(2), 145-8.

Fe Mossbauer spectroscopy has been used to study to fly ash of Panipat Thermal Power Station, Panipat andthe various samples of agriculture soil where the effluent water is used for irrigation in the adjoining areas of the Thermal Power Plant. The fly-ash sample shows only Fe²⁺ state. When the effluent water is used for irrigation, then fly-ash flows with water and gets added in the agriculture soil and thereby increases the Fe²⁺/Fe³⁺ ratio in the soil. The Fe²⁺/Fe³⁺ ratio in these samples has been determined.These results indicate that, the effluent water, when used for irrigation improves plant nutrition and the growth of the crops is good and hence reduces the applicability of artificial fertiliser up to some extent.

3 illus, 1 table, 9 ref

000075   Rajabi A A (Physics Dep, Shahrood University, P O Box 36155-316, Shahrrod, Iran) : Static properties of hadrons from MIT bag model with interacting quarks. Indian J pure appl Phys 2003, 41(2), 89-94.

An imporoved MIT bag model is used to calculate the static properties of hadrons containing u, d, s and c quarks. The two key ingredients of the improved model are the effective quark-gluon coupling constant originating from color charge and the quark confinement. Choose to allow residual interactions to operate so as to go beyond of asymptotic freedom and confinement. In the model used, the valence quarks interact with themselves. Calculates the relativistic wave-function for quarks in a scalar-vector QCD potential, analytically. Finally, vanishing of the normal component of vector current at the surface of the baryon as a boundary condition equivalent to confinement results in the static properties and the strength of Coulomb like potential parameter. This depends on the mass parameters, contrary to almost all the previous versions. The calculated static properties for baryon is better than in the uncorrected versions of the model.Magnetic moments and charge radii of some hadrons are comparable well with experiment.The agreement for the magnetic moments is surprisingly good for n, Λ, ∑^-, ∑⁺.......

1 table, 20 ref

000074   Rafi M;Al-Tuwirqi;Arafa M R;Farhan H (Physics Dep, Faculy of Science, P.O.Box 80203, King Abdulaziz University, Jeddah-215 89, Saudi Arabia) : On the prediction of w<. Asian J Spectrosc 2002, 6(3), 133-41.

A four-parameter potential function is used to predict anharmonicity constants w^ex^e of various stable diatomic molecules. The values obtained are compared with those of the other functions.

3 tables, 14 ref

000073   Purkayastha P;Sarma B K;Talukdar A N (Department of Physics, Gauhati University, Guwahati, Assam-781 014) : Crystal structure of tetrakis (imidazole) copper(II) bromide (CuBr₂C₁₂N₈H₁₂). Indian J pure appl Phys 2003, 41(5), 350-3.

The crystal and molecular structure of tetrakis imidazole copper (II) bromide (CuBr₂C₁₂N₈H₁₂)has been investigated from three-dimensional intensity data. The two imidazole rings bonded to the central Cu atom through the respective N atom, which constitutes one-half of the asymmetric unit of the centrosymmetric structure under consideration. The distance between Cu-Br^- ion id found to be 3.376(1)A which excludes the possibility of formation of any covalent bond between them.

2 illus, 2 tables, 26 ref

000072   Pradhan B;Rout G C;Behera S N (Physics Dep, Government Science College, Nuapada-766 105) : Theoretical study of superconducting gap in correlated cuprate. Indian J Phys-Pt A 2003, 77(2), 167-71.

The interplay between superconductivity (SC) and anti-ferromagnetism (AF) in strongly correlated High Temperature Superconductor systems : R^2-xM^xCuO⁴ (R <61>Nd, La, ...and M <61>Sr, Ce) is very intersting to study both theoretically and experimentally. Presens a microscopic theoretical model for the system to stduy its superconducting gap equations in absence of anti-ferromagnetism. Superconductivity is assumed to be in copper 3d electrons in presence of hybridization between conduction band and f-level of the Ce impurity atom. Green's functions are calculated by Zubarev techique and the SC gap equation was solved numerically by self-consistent method under half-filled band situation. The effect of the impurity f-level and its hybridization with conduction band on superconducting gap is investigated theoratically and results are discussed.

1 illus, 10 ref

000071   Phonate V;Malik R S;Kumar Sanjay (Soil Science Dep, CCS Haryana Agricultural University, Hisar-125 004) : Anistropy in some alluvial soil. Ann Arid Zone 2001, 40(4), 425-7.

Saturated hydraulic conductivity in vertical (KV) and horizontal (KH) directions were experimentally determined for different soil depth, i.e., 0.05 to 0.10 m, 0.15 to 0.20 m and 0.25 to 0.30 m in three alluvial soils. KH was found to be larger than KV in all soils and at all depths by a factor ranging from 1.1 to 7.2. Overall average of KH/KV ratio for all soils and depths was 2.1. There was no corresponding anisotropy in compaction in any of the soils. Higher bulk densities encountered in deeper layers indicated the formation of plough layer.

4 illus, 1 tables, 7 ref

000070   Pattanaik S R;Mishra I P;Mishra J K;Dash G N (P G Physics Dep, Sambalpur University, Jyoti Vihar, Burla-768 019) : A comparative study of v- and π-type DAR IMPATT diode structure based on InP material. Indian J Phys-Pt A 2003, 77(2), 173-5.

A comparative study of small and noise behaviour of N⁺p vnp⁺ (v-type) and n⁺pπnp⁺ (π-type) structure of DAR IMPATT diode based on InP material has been made by computer simulation method developed by our group. Both the structures are taken of a fixed width of 800 nm. Multiple peaks for negative conductance and mean square noise valtage for both type of structures. It is observed that the device negative conductance(-G^p) as well as the device negative resistance (-Z^rp) for the π-tupe InP DAR IMPATT diode is much higher than those of the v-type InP DAR IMPATT diode, both the operation in W-band and D-band. Similarly, the mean square noise voltage peaks for the π-type InP DAR IMPATT diode, are observed to be higher than the corresponding peaks of the v-type InP DAR IMPATT diode. This is obvious because of the fact that the high power generating mechanism also creates a higher noise. However, the π-tupe InP DAR IMPATT diode can be used for high power performance with a moderate noise by suitably choosing the frequency of operation.

5 illus, 8 ref

000069   Patil P S;Ennaoui E A;Fiechter S;Tributsch H; Sadale S B (Department of Physics, Shivaji University, Kolhapur-416 004) : Formation of textured WS₂ thin films by van der Waals rheotaxy process and their photoactivity. Indian J pure appl Phys 2003, 41(5), 369-73.

Photoactive thin films of tungsten disulphide (WS₂) have been prepared by sulphurization of tungsten trioxide (WO₃) thin films. WO₃ films have been deposited in an inert atmosphere onto the pre-deposited Ni coated quartz substrates by using an ultrasonic spray pyrolysis technique (USP). Subsequently, the WO₃ films have been treated at 700 °C in a sealed quartz, ampoule filled with elemental sulphur and 0.2 bar N₂/H₂ forming gas for about 6 hr. The films have been investigated by using X-ray diffractometer (XRD), scanning electron microscopy (SEM), and optical absorption techniques. The photoactivity has been measured using time-resolved microwave conductivity (TRMC) technique. For comparison, the results of WS₂ films grown on quartz substrates without pre-deposited nickel layer have been given.

5 illus, 15 ref

000068   Pati S P;Dash S K;Mishra K (Physics Dep, Sambalpur University, Jyoti Vihar, Burla, Sambalpur-768 019) : Compensation of deterioration in microwave properties of GaInAs DDD due to mobile space charge and optical injection through modulation of impurity doping. Indian J Phys-Pt A 2003, 77(2), 139-42.

GaInAs double drift diode (DDD) operating in the IMPATT mode has been designed and analyzed for several frequency bands of operation under varying operating conditions to study its microwave properties. The microwave performance characteristics shwo rapid deterioration when operating curretn density is increased (due to mobile space charge) and with the decrease of multiplication factor (due to optical injection and increase of saturation current). Devises a technique to compensate the deteriorating effects of both the factors through modulation of flat doping concentration of GaInAs diode.

3 tables, 7 ref

000067   Pati J C (NO, Stanford Linear Accelerator Center, Menlo Park, CA 94025, USA) : Probing grand unification with fermion masses, neutrino oscillations and proton decay. Pramana J Phys 2003, 60(2), 291-336.

A concrete proposal is presented within a predictive SO(10)/G(224) framework that successfully describes the masses and mixings of all fermions, including the neutrinos-with eight predictions, all in agreement with observation. Within this framework, a systematic study of proton decay is carried out, which (a) pays special attention to its dependence on the fermion masses, (b) limits the threshold corrections so as to preserve natural coupling unification, and (c) uses recently improved values of the matrix element and renormalization effects. Allowing for both minimal supersymmetric standard model (MSSM) and its proposed variant, the so-called extended supersymmetric standard model (ESSM), as effective low-energy theories, the study shows that a conservative upper limit on the proton lifetime is about (1/3-2)x10³⁴ years, with vk⁺ being the dominant decay mode, and quite possibly μ⁺K⁰ and e⁺π⁰ being prominent. This in turn strongly suggests that an improvement in the current sensitivity by a factor of five to ten ought to reveal proton decay. For comparision, some alternatives to the conventional approach to unification pursued here are mentioned at the end.

2 tables, 98 ref

000066   Parhi N;Rout G C;Behera S N (P G Physics Dep, M P C College (Autonomous), Baripada-757 001) : Interplay of ferromagnetism and static band Jahn-Teller distortion. Indian J Phys-Pt A 2003, 77(2), 153-8.

The manganite system La^1-xSr^xMnO³ is a ferromagnetic metal in presence of static Jahn-Teller distortion. The system is described by an electronic Hamiltonian containing the hopping terms as well as the ferromagnetic term arising out of the same itinerant e^g electrons of Mn ion in presence of lattice distrotion. The one particle Green's functions of the electrons are calculated by Zubarev technique using equations of motion method. The magnetization and lattice strain are calculated and solved self-consistenly taking into account the impurity and chemical potential. The interplay between ferromagnetism and lattice distrotions is discussed.

6 illus, 16 ref

000065   Panwar S;Dua P;Singh I (Department of Basic Sciences, College of Engineering and Technology, Gurukul Kangri University, Hardwar) : Anomalous hall constant of heavy fermion systems. Indian J pure appl Phys 2003, 41(5), 389-92.

The large anomalous Hall constant of heavy fermion systems can be understood using Periodic Anderson Model. A variational method in this work to study temperature variation of Hall constant R_H of cerium compounds has been used. The skew scattering plays a dominant role in deciding R_H in these compounds. The scattering phase shift is strongly magnetic field dependent and the Hall constant is expressible in terms of magnetic susceptibility.

1 illus, 21 ref

000064   Panigrahi S;Rout S K;Hassan A K;Ray A K (Physics Dep, R E College, Rourkela-769 008) : Optical parameters of spun on films of calix-4-resorcinarene molecules by attenusted total reflection technique. Indian J Phys-Pt A 2003, 77(2), 163-5.

Surface plasmon resonane (SPR) measurements under attenuated total reflection (ATR) were taken in air as well as in pure water, for an overlayer containing Calix-4-resorcinarene (Azol) molecules spum on Au coated slides. SPR data for both media used throughout this work were fitted to Fresnel reflection theory for a four layered (glass-Au-Azol-air or water) system. By varying the Azol film thickness during the fitting procedure, different solucitons have been obtained for the film dielectric constant and hence its refractive index. The refractive index versus thickness for both media were plotted and from the intersecting point of the two curves an exact solution was found which gives film optical parameters of organic overlays.

3 illus, 5 ref

000063   Pandey R S;Misra K D;Tripathi A K (Department of Applied Physics, Institute of Technology, Banaras Hindu University, Varanasi-221 005) : Generation of electrostatics ion-cyclotron wave by parallel flow velocity shear in the presence of inhomogeneous electric field in an anisotropic magneto-plasma. Indian J Radio Space Phys 2003, 32(2), 75-82.

Generation of electrstatic ion-cyclotron wave and its harmonics, driven by parallel flow velocity shear in the presence of perpendicular inhomogeneous d.c. electric field and density gradient, is studied by using the characteristic method. The details of particle trajectories, dispersion relation and growth rate have been evaluated in the short wavelength region. The ion-cyclotron waves are excited at various harmonics of ion-cyclotron frequency. The growth rate is evaluated for ion-cyclotron harmonics for plasma parameters suited to magnetosphere. The dominant driving source of this instability is found to be the parallel flow velocity shear rather than the temperature anisotropy and temperature ratios of electron and ion. The electric field inhomogeneity has a destabilizing effect on ion-cyclotron instability.

10 illus, 18 ref

000062   Panda S;Panda B K (NO, Institute ofMathematics and Applications, Bhubaneswar-751 005) : Electric field induced tunneling process in the quantum well. Indian J Phys-Pt A 2003, 77(2), 147-51.

The field induced direct tunneling and phonon-assisted tunneling of electrons from the single quantum well based on the AlGaAs/GaAs heterojunction are reported. The barrier lowering due to the applied electric field favours electrons to tunnel out of the well. The longitudinal optic phonon at a finite temperature scatters electrons to the continuum and then the electron escapes out of the well in the direction of the elctric field. The thermally excited electrons also escape from the well by the thermionic process. The dark current is calculated taking different field induced tunneling mechanisms. The electron absorbs photons and generates photo-current in the direction of the electric field. The magnitude of the photo-current is an order of magnitude higher than the dark current.

4 illus, 16 ref

000061   Panda B K (NO, Institute of Physics, Sachvalaya Marg, Bhubaneswar-751 005, Orissa) : Structure of small and intermediate size silicon cluster. Indian J Phys-Pt A 2003, 77(2), 109-15.

Tight-binding molecular dynamics methods are used to optimize geometries of mid-sized silicon clusters up to 23 atoms. The calculated equilibrium structures of the clusters are similar in both orthogonal and nonorthogonal tight-binding simulations. The results obtained in the tight-binding model are compared with those obtained using first principles methods. While in the first principles methods and experiments the structural phase transition is.expected to occure at Si²⁵. Some properties of these clusters are calculated using tight-binding methods and compared with results obtained from ab initio methods.

5 illus, 34 ref

000060   Otto A (Lehrstuhl Fur Oberflachenwissenschaft Dep, Heinrich-Heine-University Dusseldorf, 40225 Dusseldorf, European Union) : On the electronic contribution to single molecule surface enhanced Raman spectroscopy. Indian J Phys-Pt B 2003, 77(1), 63-73.

Considers single molecules in junction sites between metallic nanoparticles in small culsters. Though high electromagnetic fields can exist in these junctions, they do not increase below gap sizes, where electron tunneling sets in. Following the experimental and theoretical work on DC currents in metal-single molecule-metal systems, a model of resonant optical tunneling via the orbitals of the molecules in the jucntions is developed. Sicne "cononical-SERS" is the "many molecules-many hot sites" ensemble of SM-SERS, discusses cold-deposited silver films in this respect as ensemble of SM-junction-SERS. This is supported by DC resistance during annealing of the cold-deposited films. The individual changes of the DC resistance during exporsure of the cold-deposted films to various gases and the simulatneous development of the SERS intensity supports the model of a hybrid field-and electronic SM-SERS in junctions. In cold-deposited films, the electronic contribution to SM-SERS is about 3 orders of magnitude. One may state, that the field part in junctions enables that Raman signals can be measured, but the electronic part decides, what is seen. (when no intramolecular resonance Raman effect is involved).

16 illus, 71 ref

000059   Nayak P;Mohanty S (P G Physics Dep, Sambalpur University, Jyoti Vihar, Sambalpur-768 019) : Phonon in some fluoride scheelite. Indian J Phys-Pt A 2003, 77(2), 177-80.

The infrared and Raman scattering measurement on some Fluoride Scheelites have revealed two facts. These are (i) absence of several modes in the spectrum, which is thought to be either due to their non-identification or of non-observed nature and (ii) softening of few specific phonon modes is some systems. To account these unusual observations in some system wer propse a strong electron-phonon interaction in these systems. Considers the Periodic Anderson Model (PAM) with electron-phonon interaction as applied to Heavy Fermion (HF) systems. However unlike the case of HF systems, conjectures the coupling of phonon wiht f-electrons is stronger compared to that of hybridization. With this reproduces a large number of phonon peaks even in the static case (w <61>0) and softening.

1 illus, 9 ref

000058   Nasasry M M;Gerges M K;Shaban H T;Salwa AS (Physics Dep, Faculty of Science,South Valley University, Qena, Egypt) : Some physical properties of Ga₂Te₅ single crystals. Indian J pure appl Phys 2003, 41(2), 139-44.

Single crystals of Ga₂Te₅ were prepared by special modified Bridgman technique. Measurements of the electrical conductivity and Hall effect between 268 and 503 K were carried out on Ga₂Te₅ samples, in two crystallographic directions (parallel and perpendicular to the C-axis). The Hall coefficient is positive and varies with the crystallographic direction.A unique mobility behaviour and stron anistropy in the carrier mobility were observed. Also, the investigation involves the thermoelectric powder measurements of Ga₂Te₅ samples, in the wide range, fro 170 to 511 K, when the direction of the temperature gradient is parallel to the layer planes. The combination of the electrical and thermal measurements in the present invetigation makes it possible to find various physical parameters such as, carrier mobilities, effective masses of free charge carriers (m_pm_n), diffusion coefficient (D_DP_n) and diffusion length (L_PL_n), as well as the relaxation time (τ_Pτ_n) and to reveal the general behaviour of this semiconductor.

5 illus, 19 ref

000057   Narasimhan A V (NO, Guest Professor of Physics, Sri Sai Ram Engineering College, Chennai-600 044) : Ultrasonic relaxation in some viscoelastic liquids. Indian J pure appl Phys 2003, 41(2), 105-12.

Expressions are worked out for the ultrasonic relxation times in viscoelastic liquids, using thier compressibility (an elastic property) and bulk viscosity coeficient (a viscous property), giving equatiions for the comporessional and bulk viscous relaxation times in these viscoelastic liquids. Availabel experimental data in three viscoelastic liquids, are used to claculate these ultrasonic relaxation times, which depend upon the low, mid and high frequency wave velicities and the absorption of the wave in the medium. The complex wave velocity (Indian J Pure & Appl Phys, 12(1974) 557) is connected with the complex compressibility of the liquid, while Navier-Stokes equations of hydrodynamics (IEEE Trans on Sonics & Ultrasonics, SU 16 (1969), 182) are connected with the real and imaginary parts of the complex, bulk viscosity coefficient of liquid, leading to equations for the aforesaid relaxation times and their evaluation, using experimental data. The variations of veloctity, absorption and relaxation times with temperature have been discussed. Temperature variations of relaxation times have been discussed and are used to evaluate the molecular activation energies in the liquid. The magnitudes of the activation energies are found to be reasonalbe. The agreement between theory and experimental data seems to be better for compressinal relaxation, than for relaxation associated with bulk viscosity of the liquid. It seems that, the data can be resolved into more than one relaxation group and activation energy (two or even more)leading to a distribution of relaxation times in these viscoelastic liquids.

2 illus, 3 tables, 5 ref

000056   Nair S U K;Warriar P R S;Koshy J (Physics Dep, University College, Thiruvananthapuram-695 001) : Superconducting YBa₂Cu₃O_7-δ thick film (T_c(0)=92 K) on a newly developed perovskite ceramic substrate. Bull Mater Sci 2002, 25(2), 95-9.

A complex perovskite oxide, YbBa₂NbO₆, as a non-reacting substrate for YBa₂Cu₃O_7-δ supercondcuting film has been developed.the dielectric constant and loss factor values of the material are in the range suitable for its use as substrate for microwave applications.A YBa₂Cu₃O_{7-δ superconducting thick film dip coated on YbBa2NbO6 substrate gave a Tc (0) fo 92 K and current density of ~1.3x10<6>4} A cm^-2.

5 illus, 10 ref

000055   Mukhopadhyay P K;Das D (NO, S N Bose National Centre for basics Sciences, J D Block, Sector-III, Bidhan Nagar, Kolkata-700 098) : Sound velocity study of NiMo systems. Indian J Phys-Pt A 2003, 77(2), 159-62.

Sound velocity study of a disordered alloy system NiMo, was undertaken. The interest is to dilute a purely ferromagnetic metal with a compatible non-magnetic component and systematically study how the magnetic properties os the system changes consequently. Report the study on 10% Mo system. Besides conventional resistivity, magnetic susceptibility and Mossbauer studies, also perform sound velocity measurements on this system. The sound velocity measurements were done by a vibrating reed apparatus, and the data show close similarity with the other measrements.

4 illus, 6 ref

000054   Moretti S (NO, CERN Theory Division, CH-1211 Geneva 23, Switzerland) : Improving the discovery potential of charged Higgs bosons at the Tevatron and large hadron collider. Pramana J Phys 2003, 60(2), 369-76.

Outlines several improvements to the experimental analyses carried out at Tevatron (Run 2) or stimulated in view of the large hadron collider (LHC) that could increase the scope of CDF/D0 and ATLAS/CMS in detecting charged Higgs bosons.

4 illus, 20 ref

000053   Mondal A K;Roy S K (Physics Dep, Visva Bharati University, Santiniketan-731 235) : Effect of NDOS structure on the transition temperature and resistance anomaly in impure Zr-Cu metallic glass. Indian J Phys-Pt A 2003, 77(2), 181-6.

The suppression of superconducting transition temperature and the anomaly in the resistance peak of Zr⁵⁰Cu⁵⁰ doped with dilute anti-ferromagnetic impurities have been studied. The change in normal density and the resistivities are calculated for 11 ppm of Mn in Zr⁵⁰Cu⁵⁰. The theoretical resultes agree with the reported experimental values qualitatively justifying the model proposed.

2 illus, 7 ref

000052   Mishra V K;Tiwari D P (Department of Physics, A P S University, Rewa (M P) 486 003) : Long-term association of solar activity and cosmic ray intensity for solar cycles 21 and 22. Indian J Radio Space Phys 2003, 32(2), 65-9.

Based on the monthly data of solar flare index (SFI), instead of sunspot numbers and cosmic ray intensity (CRI) for the last two solar cycles since 1976, a detailed correlation study has been made by using the "running cross-correlation" method. It has been found that the anti-correlation between SFI and CRI is strong during ascending and descending phases of solar cycle. The observed cosmic ray modulation during these periods, when compared with other solar activity indices, shows the appropriateness of the SFI as solar activity index, instead of sunspot numbers or even the grouped solar flares (GSF). The effects are found to be distinctly different in the two solar cycles 21 and 22, when the most appropriate solar activity index SFI is used. The observed depth of cosmic ray modulation in cycle 22 is larger than that in cycle 21 in contrast to reverse tendency in SFI, which necessitates further studies on short-term basis.

3 illus, 9 ref

000051   Mandal K;Krause T W;Atherton D L (C K Majumdar Laboratory Dep, S N Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata-700 098) : Characterization of magnetic material by barkhausen noise measurement. Indian J Phys-Pt A 2003, 77(2), 93-7.

Ferromagnetic materials generate magnetic Barkhausen noise (MBN) mainly due to 180° domain wall motion. MBN measurement can be used for the characterization of magnetic materials. The direction of magnetic easy axis of a polycrystalline steel material has been studied in presence of different stresses using MBN measurement. The stress distributions around a circular shaped defect in a ferromagnetic material has also been investigated using the same measurement.

10 illus, 8 ref

000050   Kundu A (Department of Physics, Jadavpur University, Kolkata-700 032) : B decays and supersymmetry. Pramana J Phys 2003, 60(2), 345-51.

Discusses how supersymmetry affects various observables in B decays, and points out the interesting channels in the context of B factories.

23 ref

000049   Krishnakumar V;John Xavier R (Post-graduate Department of Applied Physics, Nehru Memorial College, Puthanampatti-621 007) : Normal coordinate analysis of vibrational spectra of 2-methylindoline and 5-hydroxyindane. Indian J pure appl Phys 2003, 41(2), 95-9.

The normal coordiante analysis of 2-methylindoline and 5-hydroxyindane has been carried by assuming C_s piont group symmetry. The potential energy constants are obtained by applying Wilson's FG matrix method. The potential energy distribution has also been calculated to check the validity of the assignments proposed in this study.

2 illus, 2 tables, 10 ref

000048   Krishnakumar V;Arivazhagan M (Department of Physics, Nehru Memorial College, Puthanampatti-621 007) : Vibrational and normal coordinate analysis of thymine hydrochloride. Indian J pure appl Phys 2003, 41(5), 341-5.

The FTIR and laser Raman spectra of thymine hydrochloride were recorded in the region 4000-100 cm^-1 and the normal coordinate analysis has been carried out by assuming Cs point group symmetry. All the normal modes of vibrations are assigned and calculations of potential energy distribution are also performed.

2 illus, 2 tables, 11 ref