http://nopr.niscair.res.in/handle/123456789/8226 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/8384 Title: Study of attractive hard-core Yukawa fluids of variable range <br/> <br/>Authors: Dwivedee, D K; Khanna, K N <br/> <br/>Abstract: The thermodynamic and structural properties of purely attractive hard-core Yukawa particles in the fluid state are determined in the high-temperature expansion of the mean spherical solution (MSA-HTE) to the Ornstein-Zernike equation. The radial distribution function at contact of attractive hard-core Yukawa particles is reported by introducing second order perturbation term, thus improving its accuracy. Further, systems of particles with Yukawa screening length λ = 1.8, 3.0 and 4.0 are examined and compared with the results obtained by simulation. <br/> <br/>Page(s): 845-849 http://nopr.niscair.res.in/handle/123456789/8383 Title: Laser power meter: A simple optoelectronic set-up <br/> <br/>Authors: Choudhury, D; Devi, M; Barbara, A K <br/> <br/>Abstract: The development and working of an optoelectronic set-up have been described and the reliability of this system for use as a laser power meter mainly for CW operation has been examined and adopted it as a field model. Subsequently, its performance in measurement of pulsed lasers in limited cases is also presented. <br/> <br/>Page(s): 801-804 http://nopr.niscair.res.in/handle/123456789/8382 Title: Dielectric relaxation phenomena of some aprotic polar liquids under giga hertz electric field <br/> <br/>Authors: Karmakar, A; Mitra, U K; Dutta, K; Sit, S K; Acharyya, S <br/> <br/>Abstract: The two relaxation times <img src='/image/spc_char/tow.gif' border=0> ₁ and <img src='/image/spc_char/tow.gif' border=0> ₂ due to rotations of the flexible parts and the whole molecules of some aprotic polar liquids (j) like N, N-dimethyl sulphoxide (DMSO); N, N-dimethyl formamide (DMF), N, N-dimethyl acetamide (DMA) and N, N-diethyl formamide (DEF) in benzene (i) are estimated from the measured real <img src='/image/spc_char/lembda.gif' border=0>_ij' and imaginary <img src='/image/spc_char/lembda.gif' border=0>_ij'' part of <i style="">hf</i> complex dielectric orientational susceptibility <img src='/image/spc_char/lembda.gif' border=0>_ij^* and low frequency susceptibility <img src='/image/spc_char/lembda.gif' border=0>_oij at different weight fractions <i style="">w</i>_j’s of solute at various experimental temperatures [Saha <i style="">et al.,</i> <i style="">J Phys. D: Appl Phys</i>, 27 (1994) 596]. The relative contributions <i style="">c</i>₁ and <i style="">c </i>₂ due to <img src='/image/spc_char/tow.gif' border=0> ₁ and <img src='/image/spc_char/tow.gif' border=0> ₂are calculated from Fröhlich’s equations and graphical technique. All the <i style="">c</i>’s are positive from Fröhlich’s equations while some <i style="">c</i>₂’s are negative from graphical method. The dipole moments <img src='/image/spc_char/micro.gif' border=0> ₂ and <img src='/image/spc_char/micro.gif' border=0> ₁ in Coulomb-metre (C.m) measured from the slope β’s of <img src='/image/spc_char/lembda.gif' border=0>_ij'–<i style="">w</i>_j curves are compared with those of conductivity σ_ij measurements using <img src='/image/spc_char/tow.gif' border=0> ’s from the ratio of individual slope of (d<img src='/image/spc_char/lembda.gif' border=0>_ij''/d<i style="">w</i>_j)<i style="">_w</i>_j→o and (d<img src='/image/spc_char/lembda.gif' border=0>_ij'/d<i style="">w</i>_j)<i style="">_w</i>_j→o, linear slope of <img src='/image/spc_char/lembda.gif' border=0>_ij''–<img src='/image/spc_char/lembda.gif' border=0>_ij' along with Gopalakrishna’s method [<i style="">Trans Faraday Soc</i>, 53 (1957) 767]. The estimated <img src='/image/spc_char/micro.gif' border=0> ₁’s agree with the measured and reported <img src='/image/spc_char/micro.gif' border=0> ’s to indicate that the flexible part of the molecule is rotating under GHz electric field. The theoretical dipole moment <img src='/image/spc_char/micro.gif' border=0> _theo’s are obtained in terms of available bond moments of the substituent polar groups attached to the parent molecules acting as pusher or puller of electrons due to inductive, mesomeric and electromeric effects in them under <i style="">hf</i> electric field. The variation of <img src='/image/spc_char/micro.gif' border=0> ₁ with temperature suggests the elongation of bond moments. The energy parameters such as enthalpy of activation Δ<i style="">H</i>_{<img src='/image/spc_char/tow.gif' border=0>}, free energy of activation Δ<i style="">F</i>_{<img src='/image/spc_char/tow.gif' border=0>} and entropy of activation ΔS_{<img src='/image/spc_char/tow.gif' border=0>}’s are obtained for DMSO only assuming dielectric relaxation as a rate process to know the molecular dynamics. The variation of ln(<img src='/image/spc_char/tow.gif' border=0> ₁<i style="">T</i>) against 1/<i style="">T</i> of DMSO reveals that it obeys Eyring rate theory unlike ln(<img src='/image/spc_char/tow.gif' border=0> ₂<i style="">T</i>) against 1/<i style="">T</i> curve. <br/> <br/>Page(s): 856-866 http://nopr.niscair.res.in/handle/123456789/8381 Title: Non-radiative energy transfer between Eu³⁺ and Er³⁺ ions in zinc phosphate glass <br/> <br/>Authors: Joshi, B C; Dhondiyal, Charu Ch; Upreti, D K; Khulbey, Bhawana <br/> <br/>Abstract: A study of non-radiative energy transfer in Eu³⁺-Er³⁺has been done by observing the steady state emission of Eu³⁺ with varying concentration of Er³⁺in zinc phosphate glass at room temperature. It has been observed that Eu³⁺ion emission intensity decreases with increasing Er³⁺ concentration resulting in a non-radiative energy transfer from Eu³⁺ to Er³⁺. The energy transfer mechanism for Eu-Er system is mainly found electric dipole-dipole in nature. Various parameters necessary for quantitative study e.g. energy transfer efficiencies, transfer probabilities etc. between Eu³⁺ and Er³⁺have been computed. <br/> <br/>Page(s): 811-814