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Neutron Spin Echo Spectroscopy (NSE) Group B Ilir Zoto Tao Hong Yanmei Lan Nikolaos Daniilidis Sonoko Kanai Mitra Yoonesi Zhaohui Sun 2003 Summer School NCNR, NIST Gaithersburg, MD 20890

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Dynamics of particles NMR (Pulsed Field Gradient) s and higher Dynamic light scattering s –ms, 1-100 nm NSE Time scale ~ 1 - 10 ns Size scale 1-100 Å shape fluctuations Spontaneous curvature, bending elasticity, Diffusion (T, , R k)

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Experiment Hydrophobic tail Hydrophilic head Surfactant molecule AOT Experiment I of AOT micelles in C 10 D 22 (5.4 % vol. fraction) Experiment II AOT/D 2 O/C 10 D 22 (5.4/4.6/90 % vol. fraction) Inverse microemulsion droplet D2OD2O C 10 D 22 AOT ~ 25 AOT Inverse spherical micelle C 10 D 22

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Principle of NSE n BB sample elastic scattering inelastic scattering Angle 0 0±0± Neutrons posses spin and magnetic moment. They precess in magnetic fields with the Larmor frequency that depends on the strangth of the magnetic field only. (g =1.83 10 8 s -1 T -1 ) B LL S N !

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Goal Experiment I AOT micelles in C 10 D 22 Experiment II AOT/D 2 O/C 10 D 22 microemulsion

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Results Q

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Damping frequency (Hz), a 2 1.51x10 7 Amplitude, 2 0.039 D trans (Å 2 /ns)4.2 Mean Radius(Å), R 0 34.0-35.0 Bending elastic constant, k 0.15k B T Å Å 2 /ns

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Conclusion NSE is suitable for studies on: Diffusion of micelles/microemulsion Form Deformation Rg (Å) SANS R H (Å) NSE Micelles15.916.6 Micro Emul. 35.040.0 http://dept.physics.upenn.edu/ ~pcn/mcgraw2/mcglatex.html MicellesKBTKBT AOT (25C)0.15 SOPC (18C)0.9 DAPC (5,6,7C)0.44

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Acknowledgement Dobrin P. Bossev, Steve Kline, and Nicholas Rosov NCNR, NIST

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