Abstract
The discrepancy between the width of birefringence bands and shear rate bands in the system CTAB/water is addressed using a combination of NMR spectroscopy and NMR velocimetry. In correspondence with birefringence measurements in the annular gap of a cylindrical Couette cell, 2H NMR spectroscopy indicates a separation of fluid into distinct nematic and isotropic phases. By contrast the velocity profile exhibits an extremely narrow shear band, consistent with the predictions of the lever rule. Contrary to previous assumptions, the experimental evidence points to a nematic phase with high viscosity.