[en] A phase controlled multi-beam interference is applied to excite the doped liquid crystals. Control of the phase difference between the exciting beams allows the external control of the interference pattern inside the liquid crystal. The dynamic variation of the grating is made possible with a time-dependent phase change to derive the nonlinear refractive index as well as the responding speed of the material. The induced grating structure is numerically modelled with reorientational phase gratings in the liquid crystal, and the diffraction dynamics is found to be in good agreement between theoretical and experimental results

[en] We present the first measurement of the Q²-dependence of the neutron spin structure function g₂ⁿ at five kinematic points covering 0.57 (GeV/c)² (le) Q² (le) 1.34 (GeV/c)² at x ∼ 0.2. Though the naive quark-parton model predicts g₂=0, non-zero values for g₂ occur in more realistic models of the nucleon which include quark-gluon correlations, finite quark masses or orbital angular momentum. The sensitivity of g₂ to physics beyond the simple quark-parton model provides a unique opportunity to examine QCD dynamics in nucleon structure. When scattering occurs from a non-interacting quark, a prediction for g₂ⁿ can be calculated using next-to-leading order fits to world data for g₁ⁿ. Our results show a positive deviation from this prediction indicating that contributions such as quark-gluon interactions may be important. Data were also obtained for g₁ⁿ and are consistent with a next-to-leading order fit to world data evolved to our kinematic range