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Indian Journal of Pure & Applied Physics (IJPAP) >
IJPAP Vol.44 [2006] >
IJPAP Vol.44(11) [November 2006] >
| 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 |
| IPC Code: | G01R27/26 |
| Abstract: | The two
relaxation times  1
and 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  ij' and
imaginary ij'' part of hf complex
dielectric orientational susceptibility ij*
and low frequency susceptibility oij at different weight fractions wj’s
of solute at various experimental temperatures [Saha et al., J Phys. D: Appl Phys,
27 (1994) 596]. The relative contributions c1
and c 2 due to 1 and 2 are calculated from Fröhlich’s
equations and graphical technique. All the c’s
are positive from Fröhlich’s equations while some c2’s are negative from graphical method. The dipole
moments  2
and 1 in
Coulomb-metre (C.m) measured from the slope β’s of ij'–wj curves are compared with
those of conductivity σij measurements using ’s from
the ratio of individual slope of (dij''/dwj)wj→o and (dij'/dwj)wj→o, linear slope of ij''–ij' along with Gopalakrishna’s method [Trans Faraday Soc, 53 (1957) 767]. The estimated 1’s agree with the measured and
reported ’s to indicate that the flexible part
of the molecule is rotating under GHz electric field. The theoretical dipole
moment 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 hf electric field. The variation of 1 with temperature suggests the
elongation of bond moments. The energy parameters such as enthalpy of
activation ΔH , free energy of activation ΔF and entropy of activation ΔS ’s are obtained for DMSO only assuming dielectric relaxation as a
rate process to know the molecular dynamics. The variation of ln( 1T) against 1/T of DMSO reveals that it obeys Eyring rate theory unlike ln( 2T) against 1/T curve. |
| Page(s): | 856-866 |
| ISSN: | 0975-1041 (Online); 0019-5596 (Print) |
| Source: | IJPAP Vol.44(11) [November 2006]
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