Proton Dipolar Spin-lattice Relaxation in the Smectic Phases of TBBA

Abstract

The proton dipolar spin-lattice relaxation time T _1D was measured at several Larmor frequencies in the various smectic phases of the liquid crystal terephthal-bis-butylaniline (TBBA) as a function of temperature and orientation of the sample in an external magnetic field. The angular dependent T _1D measurements are used to determine the importance of orientational order director fluctuations (ODF) in the dipolar field of the smectic phases of TBBA. In particular, the T ₁ D ⁻¹ angular dependence in the S_A phase is different from that in the S_C and S_G phases. This contrasts sharply with the T ₁ ⁻¹ angular dependence in these phases which are all similar.