K DUTTA, S K SIT and S ACHARYYA

Department of Physics, Raiganj College (University College), P.O. Raiganj, Dist. Uttar Dinajpur 733 134, India

The dielectric relaxation phenomena of rigid polar liquid molecules chloral and ethyltrichloroacetate (j) in benzene, n-hexane and n-heptane (i) under 4.2, 9.8 and 24.6 GHz electric fields at 30^oC are studied to show the possible existence of double relaxation times t₂ and t₁ for rotations of the whole and the flexible parts of molecules. The probability of showing double relaxation is more in aliphatic solvents indicating their nonrigidity. The symmetric and asymmetric distribution parameters g and d are obtained from c '_ij /c _0ij and c ''_ij /c _0ij at w_j --> 0 wherec '_ij and c ''_ij are real and imaginary parts of the complex orientational susceptibility c *_ij and c _0ij is the low frequency susceptibility which is real. c _ij 's are involved with the measured dielectric relative permittivities e '_ij, e ''_ij, e _0ij and e _¥ij of solutions. The theoretical weighted contributions c₁ and c₂ towards dielectric dispersions by Frhölich's method are compared with the experimental ones obtained from the graphical variation of c '_ij /c _0ij and c ''_ij/c _0ij with weight fractions w_j's at w_j --> 0. The measured dipole moments m ₂ and m ₁ of the whole and the flexible part of a polar molecule in terms of the linear coefficients b 's of c '_ij 's with w_j's and the estimated t ₂ and t₁ reveal their associations with aliphatic solvents. The theoretical dipole moments m _theo's from the available bond angles and bond moments of the substituent polar groups of the molecules with the estimated m 's suggest the mesomeric, inductive and electromeric effects in them under GHz electric field.

Keywords:  Relaxation time; hf conductivity; dipole moment.

Pacs Nos.  77.22.Gm