Neutron topography as a tool for studying reactive organic crystals: a feasibility study

The feasibility of using neutron topography as a non-destructive imaging technique for the study of X-ray sensitive organic single crystals, with a view to applying it to the study of reactivity in such crystals, has been tested. Crystals studied range from relatively X-ray insensitive protonated and deuterated pyrene crystals to relatively highly X-ray sensitive 2,4-hexadiynylene bis(p-toluenesulfonate) (PTS) monomer crystals. The latter crystals are readily polymerized in an X-ray beam. Results indicate that neutron topographic imaging provides little advantage over X-ray topography for either the X-ray insensitive or X-ray sensitive crystals studied here. It was concluded that this is mainly due to limitations in spatial resolution attributed to geometric effects inherent to the technique. However, for X-ray sensitive crystals, neutron topography can provide useful information, in a non-destructive way, in the form of rocking-curve data, and as such can be regarded as a useful `ally' technique to the analogous X-ray techniques. It is expected that in the case of extreme X-ray sensitivity, provided geometric losses can be minimized, neutron topography may be the only technique capable of non-destructively revealing bulk defect structures and strain distributions.