X-Ray induced radiation damage in taurine: a combined X-ray diffraction and Raman study

The impact of X-radiation on crystalline taurine has been investigated by time resolved synchrotron X-ray powder and single crystal diffraction and Raman spectroscopy. Multiple data sets have been collected at 120 and 296 K. All the observed effects of radiation, i.e. broadening and shifts of Raman and diffraction lines, a dose dependent irreversible increase in the atomic displacement parameters (ADPs) as well as in one of the unit-cell axes, and an apparent enhancement of electron density in the SO(3) group can be tentatively attributed to primary radical formation predominantly involving the SO(3) group. In secondary reactions molecular species that are distinct from taurine are created in minute quantities, thereby introducing local departure from crystalline order, i.e. enhanced static disorder and a build-up of local strain. Our study provides evidence for ascribing the linear increase in ADPs as well as the expansion of the c axis to the accumulation of foreign species in the crystal, and not to a thermal effect. Once initiated, this process appears to continue also without radiation, however, then at a much reduced rate.