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We report in this letter a rheo-optical study of the non-linear behaviour of a solution of worm-like micelles made of aqueous surfactant solutions of cetyltrimethylammonium chloride (CTAC) with sodium salicylate (NaSal) and sodium chloride (NaCl) salts. The rheological data show an asymptotic behaviour of the stress with the shear rate. This result is confirmed by the flow birefringence measurements where the birefringence intensity and the extinction angle are found to follow the same behaviour. These results, supported by an optical visualization of two phases in the plane of flow, corroborate the shear banding flow predicted by the non-linear rheology model.

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the surface ion and chemisorbed species, respectively. The reactions express that the chemisorbed species of NO and S02 molecules, that is, the nitrito, nitrato, and sulfilo species, rob the surface oxygens of the solid surface, inducing the pseudo oxygen vacancy on the chemisorption site; quasi-free electrons are freed from the pseudo oxygen vacancies according to eq 2, 4, 5, and 7. The prominent change in the electrical conductivity upon the NO chemisorption should arise from the reactions in which an NO molecule produces two quasi-free electrons, whereas an S02 molecule produces a single electron through eq 6 and 7. Also, the dissociation energy of the quasi-free electron from the oxygen vacancy due to the NO chemisorption is smaller than that due to the S02 chemisorption.Thus the defect chemical approach suggests that the surface lattice of oxides is not rigid, but movable upon chemisorption, although a more quantitative description of the defect chemical process of chemisorption needs further study.

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