Optics for Small Molecule Crystallography

The growing popularity of CCD diffraction cameras using Mo radiation to better match the pattern size to the camera area leads to the problem of reduced spot intensities due to poor structure factors at MoKa, especially for organic molecules, versus the need to overcome dark-current noise limits of the camera. These factors conspire to limit the minimum crystal size severely for practicable exposure times.

Focussing monocapillary optics offer unmatched beam intensity for low-divergence beam production compared to any other X-ray optics, at all characteristic line energies. The strong white-radiation suppression characteristics of these optics produce beams with excellent spectral properties compared to conventional filtered-radiation beams, producing much less background scatter at the detector and enhancing signal-to-noise ratio.

The increased intensity permits the collection of straucture-solution datasets from extremely small crystal volumes. Alternatively the use of interchangeable beam-limiting collimators with the optic allows the selected-area irradiation of disordered specimens, crystals with poor long-range order or polycrystalline aggregates.


The huge variety of equipment types and combinations used for small-molecule crystallography invariably requires us to produce custom-made housings in the majority of applications. Please see our Optical design criteria for the information you may need to specify an optical solution to your application, and please contact us for further details.

40-sec exposure small-molecule diffraction pattern using 50-micron beam from focussing monocapillary with 1 kW Mo sealed-tube source and CCD camera
(AXCO labs)