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Abstract
The transient behaviour of the director of a nematic mesophase subjected to spinning at frequency Ω in an applied magnetic field H 0 is investigated by E.S.R. All experiments were conducted with Ω > Ωc, Ωc = (ΔH2 0/2λ1). Here Δχ is the anisotropic magnetic susceptibility and λ1 is the rotational twist viscosity of the nematic. The theory of Leslie, Luckhurst and Smith is used to analyse Fourier transformed time domain data and their result for the dependence of ω, the director rotation rate, on Ω (ω = (Ω2 − Ω2)1/2) is confirmed for a range of values of H 0 and Ω. Values of Ωc for Phase IV, Phase V and the alkylcyanobiphenyls K15, K18 and K21 are reported. Linewidths in the frequency domain are shown to depend on the twist viscosity of the mesophase and possible evidence for micro-domains in Phase IV and Phase V is presented. The values of Ωc reported for Phase IV differ by a constant from the values calculated using literature values of Ω1 and Δχ.