Prodotti
Capitoli, Parte,Saggi, Studi, Articoli in libro
Neutron Scattering and Complementary Methods in Investations of Condensed Phase
- autori
- S. Urban, V. Domenici, J. Czub, M. Geppi, B. Gestblom, C.A. Veracini
- anno
- 2003
- tipo prodotto
- Capitolo, parte o articolo in libro
- lingua
- inglese
- casa editrice
- Janusz Chrusciel
- numero pagine
- 8
- pagina iniziale
- 121
- pagina finale
- 128
- edizione
- University of Podlasie Publishing House
- ABSTRACT
- Results of studies of 4-4'-di-n-heptylazoxybenzene (HAB) in the isotropic, nematic and smectic A phases are presented. Two experimental methods were applied: broad and dieletric spectroscopy (DS) and the nuclear magnetic resonance (NMR). The complex dielectric permittivity, epsilon*(w)= epsilon'(w)-iepsilon''(w), was measured in the frequency range 1 KHz - GHz. This allowed two main relaxation processes in all the phases studied to be separated: the low frequenciy, l.f., process connected with molecular reorientations aroung a short axes, and the high frequenc, h.f., process connected with rotations around the long axes. The measurement of 2H spin lattice relaxation times was carried out throughout the mesophase range of 10.0, 46.04 and 61.38 MHz. Using suitable theoretical models the principal components of the diffusion tensor, D// and D perpendicular, as well as the diffusion coefficients DR, relative to the internal rotation of the phenyl rings, were determined. The results of both studies are confronted and discussed.
- schede autori
- VERACINI CARLO ALBERTO