Rotatory measurements in the X-ray range with synchrotron radiation: experimental set-up and preliminary results for NaBrO3 single crystals

The specific rotation of NaBrO3 single crystals has been measured with an X-ray beam extracted from the white synchrotron radiation spectrum by a specially designed silicon monochromator-polarizer. A detailed description of the monochromator principle and expected performance is given and the characteristics of the output beam are as follows: extremely narrow angular and wavelength spread (Δtheta=7 μrad, Δlambda=8 x 10-6 A), nearly pure linear polarization (polarization ratio 2.5 x 108). The wavelength has been chosen very close to the bromine K edge (lambda-lambdasub(K)=2 x 10-3 A) in order to take advantage of possible resonant effects. The experimental set-up is of the crossed-polarizer type, the analyzer being a GaAs crystal adjusted for the 555 reflection with a Bragg angle thetasub(A) equal to 44.950. The specific rotation measured in these conditions has been found to be 0.35 +- 0.310 cm-1. An explanation is proposed for this small value. (Auth.)