016418   Page P S;Bhatt B C;Rawat N S;Mishra D R; Kulkarni M S (Radiological Physics and Advisory, Bhabha Atomic Research Centre, Mumbai-400 085, Email: bcbhatt2003@yahoo.com) : Delayed optically stimulated luminescence of Al₂O₃:Si, Ti phosphor. Indian J Engng Mater Sci 2009, 16(3), 154-6.

In some Al₂O₃ samples, the OSL is seen to decay much more slowly that we would expect due to re-trapping of the released charge in shallow traps. The preliminary studies indicate that Al₂O₃:Si,Ti has some component of delayed optically stimulated luminescence (DOSL). Therefore, DOSL in this system has been investigated in detail and relative contribution of DOSL to the CW-OSL signal has been determined. Therefore, OSL readout has been performed at elevated temperatures (in the range 27-l00°C) in order to eliminate the contribution of DOSL in the CW-OSL signal. The dependence of DOSL signal on readout temperature can be explained in terms of Arrhenius equation of thermally released charges from shallow traps. The total contribution of the DOSL to the CW-OSL intensity is estimated to be about 1.4%. Although the contribution of DOSL to the CW-OSL integral signal is much less, it is advisable that OSL measurements be performed at 75°C to avoid any contribution of DOSL signal to CW-OSL signal. The DOSL decay shows the second order exponential fit. The activation energy calculated for the trap responsible for DOSL is 0.5 ±0.04 eV.

3 illus, 16 ref

016417   Nazarov M;Tsukerblat B;Noh D Y (Materials Sciences and Engineering Dep, Gwangiu Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangiu-500 712, Email: nazarov@gist.ac.kr) : New highly efficient green phosphor for LEDs. Indian J Engng Mater Sci 2009, 16(3), 147-50.

To develop a highly energy-efficient white light sources, one needs to design highly efficient yellow, green and red phosphors, which are able to absorb excitation energy of blue LEDs and generate emissions. In this paper, results on production of a new green multiphase thiogallate phosphor [SrGa₂S₄ + MgGa₂O₂}:Eu²⁺ with improved luminescence properties have been presented. The detailed XRD analysis, Raman spectroscopy and PL study have been carried out in order to enlarge the understanding of the radiative processes in (SrGa₂S₄ + MgGa₂O₄):Eu²⁺, based on two different crystallographic phases (SrGa₂S₄) and {MgGa₂O₄}, prepared by solid state reaction at 900-1000°C during 4 h with a carbon reduction atmosphere. A model of 4f-5d optical transitions with due account for the electron-vibrational interaction is discussed. An approximate simple expression for the shape function of the broad vibronic bands with allowance for the terms corresponding to the emission (absorption) from both ground and first excited vibrational levels is given. Within this approximation we analyze the room temperature experimental data on the 4f-5d transitions in thiogallates doped with Eu²⁺ ions. The vibronic coupling parameters, Stokes shift and nephelauxetic effect for systems under study are estimated. The theoretical results are in a good agreement with the experimental data.

3illus, 4 ref

016416   Nagpure I M;Dhoble S J;Godbole S V;Bhide M K; Pode R B (Kamla Nehru College, Sakkardara Square, Nagpur-440 009, Email: indrajitnagpure@yahoo.co.in) : Eu<. Indian J Engng Mater Sci 2009, 16(3), 181-4.

Polycrystalline Na₃SO₄F:Eu and NaMgSO₄F:Eu phosphors prepared by a wet chemical method has been studied for its photoluminescence (PL) characteristics. PL emission spectra of Na₃SO₄F and. NaMgSO₄F, phosphors under 393 nm excitation (mercury-free excitation) shows very strong prominet peak at 591 nm due to ⁵D₀→ ⁷ F₁, transition and 613 nm corresponding to ⁵D₀→ ⁷ F₂ transition in the red region of the spectrum. The PL emission spectra of Eu³⁺ ion in the Na₃SO₄F:Eu and NaMgSO₄F:Eu phosphors are applicable for mercury free lamp industries.

5 illus, 25 ref

016415   Nagabhushana K R;Lakshminarasappa B N; Revannasiddaiah D;Haranath D;Fouran Singh (Physics Dep, Jnanabharathi Bangalore Univ, Bangalore-560 056, Email: bnlnarasappa@gmail.com) : Swift heavy ion induced thermoluminescence studies in polycrystalline aluminum oxide. Indian J Engng Mater Sci 2009, 16(3), 161-4.

When energetic swift heavy ions interact with matter, inelastic collision (leading to electronic energy loss-S_e) and elastic collision (leading to nuclear energy loss -S_n) take place. In the present study, the effect of energetic ion species on thermoluminescence (TL) of polycrystalline aluminum oxide (PAO) is reported. PAO pellets of 6 mm diameter are irradiated with energetic Au⁹⁺, Ni⁷⁺ and Si⁷⁺ ions for the fluence of Ixl0¹³ ions cm^-2. A single well resolved prominent TL glow with peak at 538 K is observed in Si⁺⁷ irradiated samples. However, in Ni⁷⁺ and Au⁹⁺ irradiated samples a prominent TL glow with peak at 610 K along with a shoulder at 513 K is observed. On the other hand, when PAO samples are irradiated with γ-rays two well separated TL glows with peaks at 483 K and 638 K are observed. A prominent PL emission with peak at 430 nm besides a weak emission with peak at 480 nm and a shoulder at 525 nm are observed in 120 MeV Au⁹⁺ ion irradiated samples when excited with 320 nm. These PL peaks are attributed to F, F₂⁺ and F₂²⁺-centers respectively. However, in Si⁷⁺ irradiated samples a single PL emission peak at 430 nm is observed and it is attributed to F-centers.

4 illus, 7 ref

016414   Murthy K V R;Sai Prasad A S;Subba Rao B;Rey L (Applied Physics Dep, Display Materials Laboratory, Faculty of Technology and Engineering, T, Vadodara-390 001, Email: drmurthykvr@yahoo.com) : Thermoluminescence dosimetric study of X-ray irradiated BAM:Eu. Indian J Engng Mater Sci 2009, 16(3), 169-71.

Thermoluminescence of 0.5Gy X-ray irradiated BAM:Eu has been studied. The irradiated phosphor has been studied for its TL properties after one week of irradiation and after 100 weeks of storage. The TL of BAM recoded after one week of irradiation and after 100 weeks of storage. Before storage for 100 weeks the TL of 0.5Gy X-ray irradiated phosphor displays a broad TL with a hump around 180°C followed by a peak at 273°C. After storage for 100 weeks the TL pattern entirely changed, i.e., the mixed peak emerged as two well resolved and high intensity peaks at 215 and 300°C. Normally after storage to 100 weeks, the peak at 190°C reduces its intensity or disappears in most cases, instead of that the peak appears at 215°C is a well resolved and the intensity is almost to the intensity of 300°C peak. Since the TL phenomenon observed is interesting. The two well resolved, isolated, high intensity peaks observed after 100 weeks of storage approves this BAM:Eu can be used as TL dosimetric material. The photoluminescence (PL) of BAM:Eu excited with 254 nm given an emission peak at 450 nm.

5 illus, 9 ref

016413   Moorthy D V R;Jayasimhadri M;Jang K;Suresh Kumar J;Mohan Babu A;Rana Moorthy (Physics Dep, Sri Venkateswara Univ, Tirupati-517 502) : Spectroscopic characteristics of Sm<. Indian J Engng Mater Sci 2009, 16(3), 193-6.

Reports on the preparation and characterization of Sm³⁺ doped alkaline earth potassium titanium phosphate (RKTP) glasses with molar composition of 24(NaPO₃)₆ + 30KH₂PO₄ + 25TiO₂'+ 20RC1₂ + lSm₂O₃ (R=Mg, Ca & Sr). Optical absorption spectra in the UV-VIS-NIR region reveal twelve absorption bands and are assigned to different transitions arising from the ⁶H_5/2 ground state. The energy level structure of Sm³⁺ (4f⁵) has been analyzed using the free-ion Hamiltonian model. The root mean square deviations between the experimental and calculated energies of Sm³⁺ doped MgKTP, CaKTP and SrKTP glasses are 44, 35 and 56 cm^-1 respectively and are comparable.with the earlier reports. By measuring the areas under the absorption peaks, the experimental oscillator strengths are calculated and the phenomenological JO-intensity parameters (Ω₂, Ω₄ and Ω₆) have been determined with the help of least-squares fitting approach. These parameters exhibit a similar trend as Ω₂<62>Ω₆<6 2>Ω₄ in all the three glasses. The evaluated JO parameters are then used to calculate the excited ⁴G_5/2 level radiative properties such as radiative transition probabilities (A_R), branching ratios (β_R) and lifetimes (τ_R). The emission spectra recorded by exciting with 476 nm shows four peaks at 563, 599, 649 and 714 nm and are assigned to ⁴G_5/2→ ⁶H_5/2,⁶H_7/2, ⁶H_9/2,⁶H_11/2 respectively. The experimentally observed decay profiles of the ⁴F_5/2 level of Sm³⁺ are found to be single exponential yielding the lifetimes (τ_mes) 2330, 1750 and 2320 us in MgKTP, CaKTP and SrKTP glasses respectively, which are comparable with the calculated lifetimes (τ_R) obtained from the Judd-Ofelt theory.

3 illus, 11 ref

016412   Maisnam m;Phanjoubam S;Sarma H N K;Thakur O P;Radhapiyari Devi L;Prakash Chandra (Physics Dep, Manipur Univ Canchipur, Imphal-795 003, Email: omprakasht@hotmail.com) : Influence of temperature on the dielectric behaviour of Co<. Indian J Engng Mater Sci 2008, 15(2), 199-202.

Li-Ni-Mn ferrites substituted with Co²⁺ having compositional formula Li_0.45-x/2Ni_0.1iMn_0.1Co_xFe_2.35-x/2O_{4< D> with x ranging from 0 to 0.1 in steps of 0.02 were prepared by the conventional ceramic technique. The temperature dependence of the dielectric constant and loss tangent have been investigated. The dielectric constant increased with the increase of temperature, the increase being more pronounced at lower frequencies indicating the dominant role played by the interfacial polarisation. Dielectric constant studied as a function of temperature showed peaks, which gets shifted to higher temperature as the frequency increased. The dielectric loss tangent was observed to increase with temperature. The results obtained are explained on the basis of Debye's equation.}

3 illus, 14 ref

016411   Maan A S;Goyal D R (Physics Dep, maharshi Dayanand Univ, Rohtak-124 001, Email: asmaan66@rediffmail.com) : Dielectric properties of In-Se-Te glassy alloys. Indian J Engng Mater Sci 2008, 15(2), 207-10.

In this paper, the dielectric properties of In4₄₀Se_xTe_60-x glassy alloys (x = 10, 20 & 30) have been reported. These measurements are carried out as a function of temperature and frequency in the range 120-350 K and 0.1-10 kHz respectively. The frequency and temperature dependence of dielectric constant ε' and dielectric loss ε" is almost similar in nature in all the alloys and the experimental results indicate that dielectric dispersion sets in at temperature exceeding 150 K and is more prominent at lower frequencies. ε' and ε" values as a function of temperature and frequency are maximum for x = 20 alloy, though similar behaviour is observed in all the samples. The experimental results seem to be explained in terms of the theory of dielectric dispersion based on two electrons hopping over a potential barrier. The frequency dependence of dielectric loss in present set of glasses at a fixed temperature is in good agreement with theory of dielectric dispersion.

5 illus, 21 ref

016410   Kulkarni M S;Mishra D R;Gupta S K;Sharma D N (Radiation Safety Systems Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: ksmukund@yahoo.com) : POSL studies on indigenously developed α-Al₂O₃:C. Indian J Engng Mater Sci 2009, 16(3), 151-3.

The pulsed optically stimulated luminescence (POSL) technique is known for its good signal to noise ratio, fast, and multiple readout features in radiation dosimetry in general and personnel monitoring in particular. Apart from this the POSL method also provides the estimation of the luminescence lifetime ι which cannot be measured in CW-, LM OSL techniques. The POSL signal is recorded on the indigenously developed μ-Al₂O₃:C using 532 nm diode pumped solid state laser and high intensity blue (470 nm) light emitting diode cluster for different pulse widths (5-20 us) and different repetition rates. The results are also compared with commercially available single crystal μ-Al₂O₃: C. The luminescence life time is estimated to be ≈ 35 ms is observed in both the samples. The POSL studies show the developed sample do not have long decay tail in time profile of POSL curve indicating suitability of the developed material for POSL routine dosimetry and qualitative difference of defect formation in developed sample as compared to those formed in the commercially available sample.

6 illus, 5 ref

016409   Jawahar K;Choudhary R N P (Physics and Meteorology Dep, Indina Institute of Technology, Kharagpur-721 302, Email: crnpfl@phy.iitkgp.ernet.in) : Structural and dielectric properties of L_aBi₂Fe₅O₁₂. Indian J Engng Mater Sci 2008, 15(2), 203-6.

The polycrystalline sample of LaBi₂Fe₅O₁₂ (LBIG) distorted perovskite compound is prepared using a high-temperature solid-state reaction technique. Room temperature preliminary X-ray diffraction (XRD) studies of the compound show the tetragonal splitting. It confirms the formation of single-phase compound with ≈2% of pyrochlore phase. The elemental content of the compound has been verified by energy dispersive spectroscopy (EDS) microanalysis. Microstructural analysis by scanning electron microscopy (SEM) shows that the grains are homogeneously as well as uniformly distributed throughout the surface of the sample. Dielectric studies as a function of temperature (30-360°C) at four different frequencies (1, 10, 100, 1000 kHz) yielded a dielectric anomaly at 325°C. It is interesting to note that the loss tangent (tan5) seems to be reduced at higher frequencies after reaching the instrumental saturation. Also, dielectric measurement as a function of frequency (100 Hz-1 MHz) at room temperature reveals the presence of different types of polarization mechanisms involved in the material. Again the frequency dependent loss tangent (tanδ) shows the sinusoidal variation, which is unusual for this kind of measurement. This variation has been confirmed by repeating the measurement at various temperatures.

5 illus, 32 ref

016408   Jain K;Srivastava V;Chouksey A (Electronic Materials Div, National Laboratory, Dr K S Krishnan Marg, New Delhi-110 012, Email: kiran@mail.nplindia.ernet.in) : Synthesis and optical properties of CdTe nanocrystals with improved optical properties. Indian J Engng Mater Sci 2009, 16(3), 188-92.

CdTe nanocrystals are prepared by hydrothermal route using the reaction between Cd²⁺ and KHTe in the presence of thioglycolic acid as the stabilizing agent. Hydrothermal synthesis under optimum conditions resulted in a rapid growth. CdTe nanocrystals with high PL intensity and narrow PL spectra are obtained in less time. The growth mechanism of CdTe nanocrystals is investigated. The growth rate in the initial stage of synthesis is higher in hydrothermal synthesis resulting in an increased growth in diffusion controlled focused region.

5 illus, 20 ref

016407   Chouksey P;Chandra B P;Ramrakhiani M (Post Graduate Studies and Research in Physics and Electronics Dep, Rani Durgavati Univ, Jabalpur-482 001, Email: p_chouksey31@yahoo.co.in) : Electroluminescence fo CdS nanoparticles-polyvinyl carbazole composites. Indian J Engng Mater Sci 2009, 16(3), 157-60.

In the study thin films of CdS nanoparticle-polyvinyl carbazole (PVK) composite have been prepared using chemical method. The absorption spectra and electroluminescence of the films doped with different concentrations of CdS nanoparticle have been measured. The absorption of pure PVK film starts at 290 nm wavelength in which a peak appears at 270 nm, indicating that the optical energy gap of PVK film is 4.26 eV. The absorption onset of CdS-PVK thin films is obtained at 300 nm, which gives the band gap of CdS nanoparticles as 4.13 eV. It is observed that the current varies linearly, whereas EL intensity varies non-linearly with increasing voltage. At a particular frequency, the emission starts at a particular threshold voltage and then it increases rapidly with increasing voltage. At a particular frequency and voltage, the EL intensity of the composite increases with concentration of CdS nanoparticles in PVK polymer and attains saturation at 5% CdS concentration. It is shown that the EL of CdS-PVK composites can be explained on the basis of electron acceleration-collision mechanism.

6 illus, 11 ref

016406   Bhatt B C;Page P S;Rawat N S;Mishra D R; Kulkarni M S (Radiological Physics and Advisory Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: bcbhatt2003Yahoo.com) : Effect of pre-thermal treatment on the OSL response of Al₂O₃:Si, Ti. Indian J Engng Mater Sci 2009, 16(3), 197-9.

Reported optically stimulated luminescence (OSL) characteristics of the Al₂O₃:Si.Ti phosphor along with some thermoluminescence (TL) and photoluminescence (PL) studies. The TL glow curve of this phosphor shows peaks around 158, 191, 276 and 355°C for a heating rate of 4 Ks^-1. In order to investigate the contribution of individual TL traps to OSL signal, CW-OSL was studied as a function of pre-thermal treatment in the temperature range 27-450°C. The integrated CW-OSL intensity of the phosphor remains constant up to 100°C; beyond this temperature the integrated intensity goes on decreasing with increase in temperature. After a pre-thermal treatment at 225°C the CW-OSL intensity falls by 73% of its initial value. Hence, it can be concluded that the TL traps up to 225°C are responsible for the major contribution to the CW-OSL signal in this phosphor. The OSL indicates that all the TL traps, up to 400°C, give measurable contribution to the OSL signal. The OSL signal becomes insignificant when the exposed phosphor is annealed beyond 400°C. It decreases nearly to zero for the sample annealed at 400°C as compared to the OSL intensity of the sample without any pre-thermal treatment. Optical bleaching results indicate that all the TL peaks decrease continuously as a function of bleaching time.

4 illus, 8 ref

016405   Bakshi A K;Dhabekar B S;Chatterjee S;Joshi V J;Kher R K (Radiological Physics & Advisory Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085, Email: akbakshil23@yahoo.com) : Energy response study of thermoluminescent dosimeters to synchrotron radiation in the energy range 10-35 ke V. Indian J Engng Mater Sci 2009, 16(3), 172-4.

LiF:Mg,Ti, LiF:Mg,Cu,P and CaSO₄:Dy TLDs are worldwide used in the field of medical dosimetry, personnel monitoring and environmental monitoring. In view of the wide spread applications of synchrotron radiation for material research and diagnostic radiology in particular medical imaging, the present study of the energy response of some popular TLDs was undertaken. For the energy response study the most useful energy range 10-35 keV of synchrotron radiation was chosen and the present experimental work was carried out at SYRMEP beam line of Elettra Synchrotron Accelerator facility, Bassoviza, Trieste, Italy. The LiF based TLDs in the form of chips and disc, and CaSO₄:Dy in the form of disc of thicknesses 0.8 mm and 0.4 mm made up of mixture of CaSO₄:Dy phosphor and Teflon in the weight ratio 1:3 were used. The energy of the synchrotron radiation was calibrated using a Si (111) double crystal monochromator and several thin foils starting from Zn with K_edge 9.659 keV to KI compound with AT_edge 33.169 keV. The energy response of the TLDs were normalized with respect its response to ⁶⁰Co and corresponding relative response was evaluated. It was found that for CaSO₄:Dy discs the relative response is about 12 at 25 keV which is maximum and subsequently falls down on either side of energy for both 0.4 mm and 0.8 mm thick discs. The relative response at 10 keV was found to be about 4.5 and 6 for 0.8 mm and 0.4 mm thick discs of CaSO₄:Dy respectively. Maximum relative response of LiF:Mg,Cu,P chip of thickness 0.4 mm was found to be about 1.26 at 25 keV and it also exhibited lower response on either side of energy. LiF:Mg,Ti chips and discs show maximum response at the 30 keV which were 1.33 and 1.39, respectively. At 10 keV which was the lowest energy used in the present study, the relative response was always found to be less than 1 for LiF based TLDs. The relative response of the TLDs evaluated in the present experiment was compared with the published value in the literature and also confirmed through theoretical calculation using ratio of mass absorption coefficient of these materials with respect to air.

4 illus, 3 ref

016404   Augustine M;Pius R;Mathew S;Mathew V (Post Graduate and Research Physics Dep, St. Thomas College, Palai-686 574, Email: vincentmathew@rediffmail.com) : Nonlinear wave propagation in ferroelectric/ferrite interface. Indian J Engng Mater Sci 2008, 15(2), 211-4.

The propagation of electromagnetic wave through the interface of magnetized ferrite and nonlinear ferroelectric half-spaces has been theoretically studied. A dispersion relation for the wave propagation corresponding to the TE mode has been derived and numerically solved. It is observed that the propagation is non-reciprocal. The dependence of power on frequency has also been evaluated.

5 illus, 9 ref

024830   Singh S (Phys Dep, Univ of Namibia, Private Bag 13301, Windhoek, Namibia, Email: ssingh@unam.na) : Deviation method for the measurement of refractive index of liquids using a Helium-Neon and two identical prisms. Res J Chem Envir 2005, 9(2), 18-19.

A simple method for the measurements of refractive index of liquids using a low power helium-neon laser emitting a continuous beam of wavelength 632.8 nm and two identical hollow (or one hollow and one solid) prisms has been proposed. The refractive index of liquids can be measured without knowing the refractive index of prism. The experimental values for some liquids have been presented.

3 illus, 8 ref

024829   Singh N K;Mishra S (Univ Dep of Phys, V.K.S. Univ, Ara-802 301) : Structural, dielectric and electrical properties of Ba-modified PbWO₄ ceramics. Asian J Chem 2005, 17(1), 449-56.

Polycrystalline samples of Ba-doped lead tungstate Pb₁Ba_xWO₄ (x = 0.0, 0.05, 0.10, 0.15) have been prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction studies of these compounds suggested the formation of a single-phase compound with the tetragonal crystal structure at room temperature. Detailed studies of dielectric constant (ε) and tangent loss (tan δ) as a function of frequency (400 Hz to 10 kHz) and temperature (room temperature to 598K) suggest that the above compounds are non-ferroelectric/non-polar with low activation energy, but interestingly contain space-charge polarization at high temperature.

5 illus, 2 tables, 16 ref

024828   Rout S K;Panigrahi S;Bera J (Dep of Ceram Engng, Natn Inst of Technol, Rourkela-769 008, Email: skrout@nitrkl.ac.in ) : Study on electrical properties of Ni-doped SrTiO₃ ceramics using impedance spectroscopy. Bull Mater Sci 2005, 28(3), 275-9.

The ceramics, SrTiO₃ (ST) and 0.4, 0.8 atom% Ni doped SrTiO₃, were prepared by solid state reaction route. The average grain size of undoped and doped samples was measured and found to be 1.2, 1.9 and 3.7 μm, respectively. The impedance measurements were conducted at 400-600°C to separate grain and grain boundary contributions. The grain and grain boundaries relaxation frequencies were shifted to higher frequency with temperature. Bulk resistance of doped and undoped ST ceramics was more or less the same. Single grain boundary resistance of doped sample was higher than that of undoped one, indicating that GB resistance increases with acceptor doping. Activation energies were calculated to confirm the same.

5 illus, 1 table, 14 ref

024827   Raji P;Sanjeeviraja C;Ramachandran K (Sch of Phys, Madurai Kamaraj Univ, Madurai-625 021, Email: thirumalchandran@yahoo.com) : Thermal and structural properties of spray pyrolysed CdS thin film. Bull Mater Sci 2005, 28(3), 233-8.

Using photo acoustic technique, the thermal properties of CdS thin films grown by spray pyrolysis are measured. Thermal diffusivity and conductivity in these films decrease at least two orders compared with bulk These results are compared with study on nano CdS and the other available literature. The comparison is good. The dependence of thermal diffusivity on the thickness of the layer or the size of the particles on the glass substrate are analysed from the present measurement and discussed. The dependence of thermal diffusivity on the thickness of the layer on the glass substrate is discussed.

4 illus, 5 tables, 21 ref

024826   Pastor M;Bajpai P K;Choudhary R N P (Sch of Pure & Appl Phys, Guru Ghasidas Univ, Bilaspur-495 009, Email: bajpai_pk@yahoo.com) : Synthesis and structural characterization of some Pb(B'_1/3Nb_2/3)O₃ type materials by two-stage solid-state route. Bull Mater Sci 2005, 28(3), 199-203.

Two-stage columbite solid state reaction route has been used for the preparation of Pb(B'_1/3Nb_2/3)O₃ materials (B' = Mg, Ni and Cd). The columbite precursor phase was structurally characterized using diffraction data. MgNb₂O₆ NiNb₂O₆ and CdNb₂O₆ show orthorhombic structures i.e. pure columbite phase. Final phase materials get stabilized in mixed phase. The diffraction pattern shows that it is a mixture of cubic pyrochlore and peroyskite phase. Percentage of perovskite phase was calculated using the band intensities of (110) perovskite and (222) pyrochlore peaks. The calculated percentages show the dominant perovskite phase. Possible reasons for mixed phase are discussed.

2 illus, 1 table, 17 ref

024825   Owoade O K;Olise F S (Dep of Phys, Obafemi Awolowo Univ, Ile-Ife, Nigeria, Email: felix_rsh@yahoo.co.uk) : Comparison of quantitative methods in X-ray analysis system (QXAS) software using IAEA refernece materials (IAEA-359, Cabbage and IAEA-336, Lichen). Res J Chem Envir 2005, 9(1), 33-6.

For the comparison of quantitative methods in X-ray analysis system (QXAS) software and to determine under which conditions a particular quantitative method is applicable, samples of plant-based reference materials (IAEA-359, Cabbage and IAEA-336, Lichen) were analyzed by energy dispersive X-ray fluorescence (EDXRF) technique. Three methods, viz: Simple Quantitative (SQ), Emission-Transmission (ET) and Full-Fundamental Parameter (FFP) were used for the elemental quantification of the samples and the concentrations compared with the reference. The concentrations of trace elements measured in both samples were in good agreement with the certified values when correct dark matrix information was supplied for each sample analyzed. Significant deviations were observed for wrong dark matrix information inputs as well as total absence of dark matrix data. The FFP method was observed to give the best quantification results and is therefore recommended for application when dark matrix information of samples is known.

4 tables, 9 ref

024824   Kunte G V;Ail U;Shivashankar S A;Umarji A M (Mater Res Cent, Indian Inst of Sci, Bangalore-560 012, Email: umarji@mrc.iisc.ernet.in) : Dip-coated hydrotungstite thin films as humidity sensors. Bull Mater Sci 2005, 28(3), 243-248.

Thin films of a hydrated phase of tungsten oxide, viz. hydrotungstite, have been prepared on glass substrates by dip-coating method using ammonium tungstate precursor solution. X-ray diffraction shows the films to have a strong b-axis orientation. The resistance of the films is observed to be sensitive to the humidity content of the ambient, indicating possible applications of these films for humidity sensing. A homemade apparatus designed to measure the d.c. electrical resistance in response to exposure to controlled pulses of a sensing gas has been employed to evaluate the sensitivity of the hydrotungstite films towards humidity.

6 illus, 17 ref

024823   Alemdar A;Oztekin N;Erim F B;Ece O I;Gungor N (Dep of Phys, Istanbul Tech Univ, 34469, Maslak, Istanbul, Turkey, Email: nurfer@itu.edu.tr) : Effects of polyethyleneimine adsorption on rheology of bentonite suspensions. Bull Mater Sci 2005, 28(3), 287-91.

The influence of the cationic polymer, polyethyleneimine polymer (PEI) on the flow behaviour of bentonite suspensions (2%, w/w), was studied. XRD, zeta potential and adsorption studies were done together with rheological measurements. The addition of PEI at concentration ranges of 10^-5-4-5 g/l and their rheological properties and stability of bentonite suspensions were studied. The adsorption rates for the bentonite suspensions are very fast. The XRD results showed that the PEG molecules did not intercalate into the layers of the clay.

5 illus, 19 ref

023844   Yadav S;Bandyapadhyay A K (National Physical Laboratory, , Dr K S Krishnan Marg, New Delhi-110 012) : Calibration of electromechanical type direct pressure indicating devices and evaluation of associated uncertaintines. MAPAN 2005, 20(1), 71-91.

In the electromechanical type direct indicating devices, the applied pressure is directly measured by a sensing element with a suitable mechanism for an analog/digital electrical signal in terms of voltage, current or frequency. The generation of such signals transforming is based on some electromechanical effects viz. inductive, capacitive, resistives, piezoelectric, piezoresistive, reluctive, resonative and optoelectic, etc. a wide range of such pressure measuring instruments is now commercially available and a lot of research is going on to improve their performances. It is clear that the transformation of electrical signal to output pressure should be highly linear, reproducible, minimum zero shift and thereby should ensure the lowest measurement uncretainty, particularly in the fluid media. The calculation of the calibration results and associated uncertainties is a complex matter involving many influencing quantities. The present paper describes three different methods for evaluating through statistical analysis of errors, the uncertainty in pressure measurement using electromechanical type direct pressure indicating device. The method of evaluation of associated uncertainties is in line with ISO/EA Guidelines on the evaluation and expression of uncertainty in measurement. The results thus obtained using three different methods are quite comparable.

6 illus, 7 tables, 26 ref

023843   Ullner C (Federal Institute for Materials Research and Testing (BAM), , 12200 berlin, Germany) : Development of the instrucmented indentation test. MAPAN 2005, 20(1), 43-52.

An overview is given about the international standard ISO 14577 on the instrumented indentation test. Main points are the metrological aspects concerning machine compliance, indenter area function, and depth zero point.

5 illus, 3 tables, 19 ref

023842   Titus S S K;Jain S k;Anil Kumar;Jain K K (Force and Hardness Standard, National Physical Laboratory, New Delhi-110 012) : Hardness and microstructure studies of standard hardness blocks. MAPAN 2005, 20(1), 37-41.

A systematic study has been undertaken on the standard hardness blocks procured from different sources in order to understand their long term stability under the permitted tolerances of the standard. As these standard hardness blocks are used as transfer standards by the industries to varify/calibrate their hardness testing machines, the reliability of these hardness blocks is of prime importance for achieving compatibility in the measurement. An effort has therefore been made to study the repeatability, microstructure and surface roughness of these standard hardness blocks with a view to improve upon the quality, reliability and reproducibility of the standard hardness blocks.

5 illus, 1 table, 9 ref

023841   Stibler A (Laboratory for Metrology, Slovenian National Building and Civil Engineering Institute - ZAG, Dimiceva 12, 1000 Ljubljana, Colvenia) : Review of hardness measurement methods for rubber and plastics. MAPAN 2005, 20(1), 53-61.

The paper gives an overview of hardness measurement methods for rubber and plastics. Recent developments of the standardization of these hardness measurement methods are presented. Especially the metrological requirements for the measuring instruments and new methods for their calibration and verification are introduced.

7 illus, 8 tables, 12 ref

023840   Singh K;Singh R P (Physics Dep, Banaras Hindu University, Varanasi-221 005, Email: kalpanasingh@myself.com) : Simulation of electromagnetic signals propagating through magnetoplasma. Curr Sci 2005, 88(10), 1562-72.

Developes a silmulation technique to obtain the dynamic spectra of electromagnetic signals propagating through an inhomogeneous magnetoplasma. The Max well's equations and equation of motion are solved to determine the expression for wave fields. By expressing the excitation source in terms of Dirac delta function, the exact frequency-time dependence of the propagating non-monochromatic singnal in computed for different magnetoplasma models. The results are further used to obtain the dynamic spectra of whistler mode waves propagating through different regions of the terrestrial magnetosphere, which have wide applications in the diagnostics of magnetospheric parameters. It is interesting to observe that the technique used under variousconditions simultaneously explains low dispersion whistlers, nose whistlers, precursors and piroton whistlers. Finally, attempts to explain whistler mode waves observed particularly at low latitude Indian ground stations.

5 illus, 37 ref

023839   Polzin T (Materialprufungamt Nordrhein-Westfalen, , Marsbruchstr-186, D 44285, Dortmund, Germany) : Requirements for the accreditation of hardness testing laboratories. MAPAN 2005, 20(1), 63-9.

Main items are gathered for the requirements for the accreditation of hardness testing laboratory.

2 illus, 1 table, 22 ref

023838   Low S (National Institute of Standards and Technology, , 100 Bureau Drive, Stop 8553, Gaithersburg, MD 20899, USA) : State of the art of the conventional hardness measuring methods: rockwell, brinell and vickers. MAPAN 2005, 20(1), 15-24.

The conventional hardness methods, Rockwell, Brinell and Vickers, have been used extensively by industry for many decades. In the past decade, there have been significant technological advancements in the designs and operation of machines used to make these hardness measurements, while continuing to follow the prescribed hardness methods specified in the test method standards. Improved systems for obtaining and ensuring traceability have also been instrumental in the advancement of hardness measurement throughout the world.

5 illus, 8 ref

023837   Kompaatscher M (NO, , Proceq SA Ringstrasse 2, Postfach 336 CH-8603 Schwerzenbach ZH, Switzerland) : Dynamic hardness measurements. MAPAN 2005, 20(1), 25-36.

Hardness tests have always been important to conclude on specific mechanical properties of materials in a fast and economics manager, i.e. in a (quasi) non destructive test. This paper gives a general overview on dynamic hardness testing and has its focus on the most recent test method, the dynamic rebound hardness test method after D. Leeb. The EQUOTIP, Leeb's original instrument, is fully discussed and newest improvements are presented. So far, Proceq SA, Swiss manufacturer of the instruments, maintained and protected the constancy of the L-Value over the last 30 years. Recent round robin results show the way, where standardization work can be improved to hold the high level of reliability of the measuring base, the L-Value.

7 illus, 13 ref

023836   Herrmann K (Physikalisch-Technische Bundesanstalt, , Bundesallee 100, 38116 Braunschweig, Germany) : Guidelines for the evaluation of the uncertainty of hardness measurements. MAPAN 2005, 20(1), 5-13.

The paper presents the basic ideas of the guidelines for the determination of uncertainty which at present are introduced in the ISO standards on the conventional hardness measuring methods Rockwell, Vickers, Brinell and Knoop. They are based on general guidelines for the evaluation of the uncertainty of measurements published by ISO (guide to the Expression of Uncertainty in Measurement - GUM and EA.

1 illus, 11 tables, 7 ref

023835   Gopinath T;Das R;Anil Kumar (Department of Physics, Indian Institute of Science, Bangalore-560 012) : Quantum information processing by NMR: implementation of inversion-on-equality gate, parity gate and fanout gate. Proc Indian Natn Sci Acad-Pt A 2004, 70(5), 649-58.

While quantum information processing by nuclear magnetic resonance (NMR) with small number of qubits is well established, implementation of lengthy computations has proved to be difficult due to decoherence/relaxation. In such circumstances, shallow circuits (circuits using parallel computation) may prove to be realistic. Parity and fanout gates are essential to create shallow circuits. In this article, it implements inversion-on-equality gate, followed by parity gate and fanout gate in 3-qubit systems by NMR, using evolution under indirect exchange coupling Hamiltonian.

7 illus, 3 tables, 42 ref

023834   Chaudhuri A (Advanced Surface Technologies, , 2/402, The Palms, South City I, Gurgaon-122 001, Haryana) : Ophthalmic lenses for vision correction: review of application, usage and trends. Trans Indian Ceramic Soc 2005, 64(1), 1-12.

This paper aims at providing an overview of the current status and the trends in the manufacture and use of the mineral lenses, but it briefly touch upon the trend towards newer organic materials that are substituting inorganic glass. The glass itself is evolving, both through improved composition and value added treatments like photochromic treatment, polarizing filters, and antireflection coatings. It examines these important treatments in detail, and also briefly look at some newer coatings and treatments that are emerging in this field.

10 illus, 9 tables, 25 ref

022854   Workalemahu B (Phys Dept, Addis Ababa Univ, P O Box 32762, Addis Ababa, Ethiopia) : Absolute thermo-electric power in heavily doped n-type silicon. Indian J pure appl Phys 2005, 43(4), 270-2.

The absolute thermoelectric power in a heavily doped n-type silicon by taking into account the effect of band tails has been calculated. The calculations show that the effect of incorporating the band tails results in increasing the value of absolute thermoelectric power.

1 illus, 8 ref

022853   Verma K K;Tiwari R S;Srivastava O N (Dep of Phys and Electron, Dr R M L Avadh Univ, Faizabad-224 001) : Effect of annealing temperature on the structural-microstructural and electrical characteristics of thallium bearing HTSC films prepared by chemical spray pyrolysis technique. Bull Mater Sci 2005, 28(2), 151-4.

In order to get good quality reproducible films of Tl : HTSC system, we have studied the different annealing conditions to finally achieve the optimized annealing condition. In the present investigation, Tl-Ca-Ba-Cu-O superconducting films have been prepared on YSZ (100) and MgO (100) single crystal substrates via precursor route followed by thallination. The post deposition heat treatments of the precursor films were carried out for various annealing temperatures (870°C, 890°C) and durations (1 and 2 min). The optimized thallination procedure occurred at 870°C for 2 min into good quality films with T_c (R = 0) <126> 103 K for YSZ and T_c (R = 0) - 98 K for MgO substrates, respectively. Further authors has correlated the structural/microstructural characteristics of the films.

3 illus, 24 ref

022852   Venkata Ramana G;Rajagopal E;Murthy N M (Sree Lakshmi Sreenivasa Degree Coll, , Pullareddy Peta, Kadapa-516 175) : Ultrasonic studies on dilute solutions of water in n-alcohols and 2-alkoxyethanols. Indian J pure appl Phys 2005, 43(4), 259-64.

Ultrasonic velocities in dilute solutions of water in n-alcohols (methanol, ethanol, n-propanol and n-butanol), and 2-alkoxyethanols (2-methoxyethanol, 2-ethoxyethanol and 2-butoxyethanol) have been determined at 298.15 K using single crystal variable path interferometer working at 3 MHz. The excess ultrasonic velocities have been evaluated using the formula, which is thermodynamically valid. A distinctive non-linear variation of ultrasonic velocity with concentration of water in both n-alcohols and 2-alkoxyethanols has been observed over a small range of concentration. A similar behaviour is also observed in the concentration dependence of excess ultrasonic velocity in these solutions. The behaviour has been explained by considering the existence of water molecules as monomers up to certain optimum concentration, (X₂)opt, of water and the non-linear behaviour observed beyond (X²) has been explained in the light of water-water and water-alcohol interactions leading to the formation of islands of water-alcohol extended structures.

4 illus, 2 tables, 35 ref

022851   Varshney D;Dube A;Choudhary K K;Singh R K (Sch of Phys Vigyan Bhawan, Devi Ahilya Univ, Khandwa Road Campus, Indore-452 017) : Superconductivity and electrical resistivity in alkali metal doped fullerides: Phonon mechanism. Bull Mater Sci 2005, 28(2), 155-71.

Authors consider a two-peak model for the phonon density of states to investigate the nature of electron pairing mechanism for superconducting state in fullerides. The first study intercage interactions between the adjacent C₆₀ cages and expansion of lattice due to the intercalation of alkali atoms based on the spring model to estimate phonon frequencies from the dynamical matrix for the intermolecular alkali-C₆₀ phonons. Electronic parameter as repulsive parameter and the attractive coupling strength are obtained within the random phase approximation. Transition temperature, T_c, is obtained in a situation when the free electrons in lowest molecular orbital are coupled with alkali-C₆₀ phonons as 5 K, which is much lower as compared to reported T_c (≈ 20 K). The superconducting pairing is mainly driven by the high frequency intramolecular phonons and their effects enhance it to 22 K. To illustrate the usefulness of the above approach, the carbon isotope exponent and the pressure effect are also estimated. Temperature dependence of electrical resistivity is then analysed within the same model phonon spectrum. It is inferred from the two-peak model for phonon density of states that high frequency intramolecular phonon modes play a major role in pairing mechanism with possibly some contribution from alkali-C₆₀ phonon to describe most of the superconducting and normal state properties of doped fullerides.

6 illus, 63 ref

022850   Vaish S K;Anupam Singh;Singh A K;Mehrotra N K (Dep of Phys, Univ of Lucknow, Lucknow-226 300) : Study of NMR spin lattice relaxation of several aldehydes. Indian J pure appl Phys 2005, 43(4), 295-300.

The NMR spin lattice relaxation of various aldehydes has been investigated. The experimental values of NMR spin lattice relaxation time T₁, of benzaldehyde, anisaldehyde, o-cholorobenzaldehyde and p-hydroxybenzaldehyde have been correlated with the calculated value of N M R spin lattice relaxation time T₁, obtained using various equations for dielectric relaxation time τ. It has been concluded that Writz equation and Murty equation are better substitute for the collation time in calculating NMR spin lattice relaxation time than Debye equation as used by BPP (Bloembergen, Purcell and Pound).

1 illus, 3 tables, 21 ref

022849   Vaid R;Padha N (Dep of Phys & Electron, Univ of Jammu, Jammu-180 006) : Novel power VDMOSFET structure with vertical floating islands and trench gate. Indian J pure appl Phys 2005, 43(4), 301-7.

A novel power (vertical double-diffused MOSFET) structure, simulated using PISCES-II, a 2-dimensional numerical device simulator has been described. The proposed device structure is based on the floating islands (FLI)-diode concept and trench gate technology. Extensive simulations were performed to understand physics of the device through various internal electrical quantities like potential distribution, electric field, etc. in different regions of the device both in on/off states. The simulation results show that the new device has a low on-resistance by virtue of reduced electric field in its drift region as well as due to the removal of parasitic JFET region resistance. Trench gate acts as a field plate to avoid the punch-through thus enhancing the breakdown voltage. For a 100 Volts design, an approximate 15% increase in the breakdown voltage has been observed in the proposed device compared to the conventional FLIMOSFET without trench gate.

6 illus, 19 ref

022848   Singh R J;Sharma P K (Phys Dep, AMU, Aligarh-202 002, Email: ranajsingh@yahoo.com) : Magnetic order and electrical resistance in manganites. Indian J pure appl Phys 2005, 43(4), 273-8.

The electrical resistance versus temperature behaviour of the manganites La_1-xBa_xMnO₃ (x=0.3, 0.4, 0.5); La_1-x, Pb_x MnO₃ (x = 0.2, 0.3, 0.33) and La_1-x Sr_x MnO₃ (x = 0.1, 0.2, 0.4) has been investigated. The temperatures at which the substances have maximum resistance have been found to be much lower than their Curie temperatures. The variation of resistance with temperature is not smooth, but the graphs show different slopes. The electron paramagnetic resonance of these substances shows a new signal in the spectra on a little increase of microwave field from the usual values. It has been interpreted as phase separations in the materials with Mn⁺³ and Mn⁺⁴ spins aligned in opposite directions. Based on this idea, magnetic order and electrical resistance of the materials are shown to be directly correlated.

4 illus, 31 ref

022847   Singh A;Vishwanadham C S;Padma N;Aswal D K (Tech Phys & Prototype Engng Div, Bhabha Atom Res Cent, Mumbai-400 085) : Growth and characterization of La_1-xPb_xMnO₃ thin films. Bull Indian Vacuum Soc 2005, 8(2), 19-29.

Thin films of Lo_1-x Pb_xMnO₃ (LPMO) have been prepared by Pulsed Laser Deposition (PLD) technique. The structural, morphological and magnetotransport properties of LPMO films are found to be strongly influenced by the growth temperature (Ts) and Oxygen partial pressure (pO₂). In the temperature range 600°C ≤ Ts<60> 800°C deposition yields single-crystalline film (SC). In this temperature range an increase in c-lattice parameter and decrease in insulator-metal transition temperature with increasing growth temperature has been observed, which are found to be consequence of the loss of Pb content at the elevated temperature. Deposition in the temperature range 500°C ≤ Ts <60> 600°C results in the growth of Nanocrystalline (NC) and Polycrystalline (PC) films. The grown NC films, having an average crystallite size of 17 nm, exhibited a record magnetoresistance (MR) value of 103% at a field of 1 Tesla.

16 illus, 11 ref

022846   Singh A;Sharma S K;Jaiswal S K;Ojha V N (NO, JVS & DC Standards, Dr K S Krishnan Road, New Delhi-110 012) : Application of automation in calibration of multimeter using precision calibrator. Bhartiya Vaigyanik Evam Audyogik Anusandhan Patrika 2005, 13(1), 74-7.

In computer age, there is an important contribution of automation in improving the error free precision calibration and to save the time. Automatic measurement is normally done using computer in high precision system and calibration. Authors discuss in detail about the automatic process and as a case study the precision calibration of digital multimeter by high precision calibrator traceable to "National Standard". The commercial software MET/CAL was used in the automation. Authors also discuss the process of the validation of this software prior to its use. The uncertainty evaluation reported in the paper is as per the ISO "GUM" document.

2 illus, 1 table, 10 ref

022845   Shashikanth P B;Rajgopal K;Beyene B;Prasad P B V (NO, SR Res Laboratory for Stud in Crystallization Phenomena, 10-1-96, Mamillaguda, Khammam-507 001) : Variable temperature oblique incidence reflection microscopy (VTOIRM) studies on (110) face of palmitic acid crystals. Indian J Engng Mater Sci 2005, 12(2), 155-7.

Modification notice in the (110) face of palmitic acid crystals, due to slow heating, detected by VTOIRM, is interpreted in terms of two phase transitions, WBB (weak bond breaking) and SBB (strong bond breaking) promoted by anisotropy in interaction energies.

3 illus, 12 ref

022844   Sharma N K;Anbarasan P M (Dep of Phys, Kanchi Mamunivar Cent for Postgrad and Res Stud, Lawspet, Pondicherry-605 008, Email: anbarasanpm@rediffmail.com) : Point contact one injection current in solid insulators with traps. Indian J pure appl Phys 2005, 43(4), 308-10.

One injection current in insulator has been studied widely for a long time in various geometries. An important field for study is the analytical treatment of current carriers in deep trap region well below the fermi level. In the problem, a cylindrical structure has been taken into consideration. The effects of traps are included in the analysis. The problems becomes complicated in the presence of traps and thermal free carriers because there are various transitions regimes in the complete current-voltage characteristics.

2 illus, 7 ref

022843   Senth Kumar V;Venkatachalam S;Narayanadass S K;Mangalaraj D (Thin Film Laboratory Dep of Phys, Bharathiar Univ, Coimbatore-641 046) : Composition, structural and electrical properties of InSb thin films. J Instrum Soc India 2005, 35(2), 239-42.

Indium Antimonide (InSb) thin films were prepared onto well-cleaned glass substrates by vacuum evaporation under a vacuum of 3 x 10^-5 Torn The compositional, structural and electrical studies have been made using Auger Electron Spectroscopy (AES), X-ray diffraction (XRD) and four-probe methods respectively. The composition of the deposited film is found to be 52.9% (In) and 47.1% (Sb). The X-ray diffractogfam revealed that the deposited films were found to be amorphous for lower thicknesses (d =1060, 1154 Angstrum) and for higher thickness (1438 Angstrum) the film were found to be polycrystalline. The particle size, strain and dislocation density values are found to be 25.18 nm, 1.81 x 10^-3 lin<^{-2/m-4 and 1.58xl015 lin/m2 respectively.}

3 illus, 9 ref

022842   Sarma R;Baishya B (Dep of Phys, J B Coll, Jorhat, Assam) : A study of the effect of ambient atmosphere and temperature on CdSe-La₂O₃+Nd₂O₃ TFT. J Instrum Soc India 2005, 35(2), 186-91.

Multiple pump down (MPO) method of thin film active devices fabrication has been employed to fabricate CdSe-La₂O₃+Nd₂O₃ Thin Film Transistor. The various layers of thin four-layered device were deposited on ultrasonically and chemically cleaned glass substrates in vacuum, better than 8 x 10^-6 torn. The length of the channel was 50 μm and its width of 148 μm. The devices were exposed to ambient atmosphere and various characteristics were observed and presented. The effect of working temperature on the characteristics of fresh TFT was also studied. From the slopes of the Arrhenius plots of log drain current vs 1000/temperature at fixed drain and gate voltage, potential barrier height were estimated and are presented. The potential barrier height of this device decreases drastically as gate voltage increases. Lowering the potential barrier by gate voltage results in increasing the effective mobility of the devices.

5 illus, 10 ref

022841   Roy S B;Chaddah P (Low Temperature Phys Laboratory Cent for Advd Technol, , Indore-452 013) : First order magneto-structural phase transition in various functional materials. Curr Sci 2005, 88(1), 71-7.

First order magneto-structural transition plays an important role in the functionality of various magnetic materials of current interest. Rare-earth manganese oxide systems showing colossal magnetoresistance and Gd₅ (Ge, Si)₄ alloys showing giant magnetocaloric effect are typical examples of such functional materials. The key features of this magneto-structural transition in these two quite distinct types of materials are phase-coexitence and metastability. Highlight this generality by comparing the experimental results with those obtained in another class of magnetic materials. A generalized framework of disorder broadened first order phase transition in intraduced to understand the interesting experimental results which have some bearing on the functionality of the concermed materials.

5 illus

022840   Reddy R R;Rama Gopal K;Ahammed Y N;Basha D B; Narasimhulu K;Reddy L S S (Dep of Phys, Sri Krishnadevaraya Univ, Anantapur-515 003) : Spectroscopic studies of molecules observed in comets. Indian J pure appl Phys 2005, 43(4), 237-45.

The potential energy curves for the different electronic states of molecules like N₂⁺, N₂, OH and S₂ observed in comets are constructed by using the Rydberg-Klein-Rees method as modified by Vanderslice el al. The ground state dissociation energies are determined by curve fitting technique using the five parameter Hulburt-Hirschfelder (H-H) function. The estimated dissociation energies are 8.587 ± 0.248, 9.620 ±0.275, 4.308 ±0.118 and 4.325 ± 0.115 eV for N₂⁺, N₂, OH and S₂ respectively. These values are in good agreement with the literature values. The r-centroids and Franck-Condon factors (FC factors) for the band system of A-X system of N₂⁺ and A-X and B-X system of N₂ molecules have been calculated employing approximate analytical methods of Jarmain and Fraser and Nicholls and Jarmain. The absence of the bands in these, systems is explained.

4 tables, 41 ref

022839   Om Kar Nath (L F & HF Impedance Stand Sect, Natn Phys Laboratory, New Delhi-110 012) : The impedance standards at National Physical Laboratory and global MRA. Bhartiya Vaigyanik Evam Audyogik Anusandhan Patrika 2005, 13(1), 81-5.

The impedance standards section at the National Physical Laboratory has established primary standards of impedance and associated calibration facilities. These facilities are used to calibrate impedance standards and associated instruments available in echelon II level laboratories in India. As such measurement traceablity has been established at national level. International intercomparison of these standards is also done time-to-time with national laboratories of other countries; such as USSR, Germany, Countries of Asia Pasific region and South Africa etc. Thus National Physical Laboratory (India) has established impedance standards having traceability both at national and international level. As such a well structured measurement system in the area of impedance standardization has been established, which provides a strong foundation for our country to enter in global market for international trade. The above mentioned impedance standards and associated facilities have been included in the BIPM global MRA. This would help to overcome Technical barriers to trade (TBT) in global market and further strengthen the Indian economy in this area.

1 table, 4 ref