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Title: Dielectric relaxation phenomena of some aprotic polar liquids under giga hertz electric field
Authors: Karmakar, A
Mitra, U K
Dutta, K
Sit, S K
Acharyya, S
Keywords: Dielectric relaxation
Aprotic polar liquids
Dipole moment
Issue Date: Nov-2006
Publisher: CSIR
Series/Report no.: G01R27/26
Abstract: The two relaxation times <img src='/image/spc_char/tow.gif' border=0> <sub>1</sub> and <img src='/image/spc_char/tow.gif' border=0> <sub>2</sub> 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><sub>ij</sub>' and imaginary <img src='/image/spc_char/lembda.gif' border=0><sub>ij</sub>'' part of <i style="">hf</i> complex dielectric orientational susceptibility <img src='/image/spc_char/lembda.gif' border=0><sub>ij</sub><sup>*</sup> and low frequency susceptibility <img src='/image/spc_char/lembda.gif' border=0><sub>oij</sub> at different weight fractions <i style="">w</i><sub>j</sub>’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><sub>1</sub> and <i style="">c </i><sub>2</sub> due to <img src='/image/spc_char/tow.gif' border=0> <sub>1</sub> and <img src='/image/spc_char/tow.gif' border=0> <sub>2 </sub>are 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><sub>2</sub>’s are negative from graphical method. The dipole moments <img src='/image/spc_char/micro.gif' border=0> <sub>2</sub> and <img src='/image/spc_char/micro.gif' border=0> <sub>1</sub> in Coulomb-metre (C.m) measured from the slope β’s of <img src='/image/spc_char/lembda.gif' border=0><sub>ij</sub>'–<i style="">w</i><sub>j</sub> curves are compared with those of conductivity σ<sub>ij</sub> 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><sub>ij</sub>''/d<i style="">w</i><sub>j</sub>)<i style=""><sub>w</sub></i><sub>j</sub>→o and (d<img src='/image/spc_char/lembda.gif' border=0><sub>ij</sub>'/d<i style="">w</i><sub>j</sub>)<i style=""><sub>w</sub></i><sub>j</sub>→o, linear slope of <img src='/image/spc_char/lembda.gif' border=0><sub>ij</sub>''–<img src='/image/spc_char/lembda.gif' border=0><sub>ij</sub>' 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> <sub>1</sub>’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> <sub>theo</sub>’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> <sub>1</sub> with temperature suggests the elongation of bond moments. The energy parameters such as enthalpy of activation Δ<i style="">H</i><sub><img src='/image/spc_char/tow.gif' border=0> </sub>, free energy of activation Δ<i style="">F</i><sub><img src='/image/spc_char/tow.gif' border=0> </sub> and entropy of activation ΔS<sub><img src='/image/spc_char/tow.gif' border=0> </sub>’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> <sub>1</sub><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> <sub>2</sub><i style="">T</i>) against 1/<i style="">T</i> curve.
Description: 856-866
ISSN: 0975-1041 (Online); 0019-5596 (Print)
Appears in Collections:IJPAP Vol.44(11) [November 2006]

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