Material Science, Chemistry, and Physics: Time-Resolved X-ray Scattering

Since its foundation, BioCARS has served time-resolved macromolecular crystallography community at the Advanced Photon Source. A recent upgrade of our 14-ID beamline increased the X-ray flux density by a factor of 100, improved pump-probe time-resolution to 100 ps, enabled us to use the widely-available 24-bunch mode of operation of the APS, and thus allows us to conduct time-resolved experiments for about 4000 hours per year (Graber et al., 2011). We also expanded our scientific reach beyond macromolecular crystallography to biological SAXS/WAXS. In addition, our upgraded technical capabilities have proved to be suitable to and attracted the attention of the time-resolved X-ray scattering community in the physical sciences.

Physical sciences user projects successfully conducted at 14-ID include photo-switching dynamics in spin-crossover molecular complexes (Collet et al, 2012), charge transfer and excited state structures in small molecules (Makal et al, 2012), X-ray pump optical probe cross-correlation study of GaAs (Durbin et al., 2012), time-resolved diffuse scattering to study the structural dynamics of photo-excited bismuth (Chen et al., 2013) etc.

14-ID capabilities for time-resolved science:

• Picosecond and nanosecond lasers synchronized with X-ray pulses are available for pump-probe experiments (< 5ps rms timing jitter)
• Single 100ps X-ray pulse isolation by an X-ray shutter system allows pump-probe time delays of arbitrary length (from 100 ps to ms, and longer)
• 100ps pulse isolation is possible in both hybrid and 24-bunch modes of the APS storage ring
• Both polychromatic (pink and white) and pulsed monochromatic (7-20 keV) X-ray beams are available
• High X-ray flux per single 100ps X-ray pulse: 3 X 10¹⁰ photons/pulse (with two in-line undulators, polychromatic pulses, hybrid mode of the APS storage ring)
• Two in-line undulators, U23 and U27; possible to modify the X-ray spectrum by offsetting the energies of the first harmonic for two undulators and/or tapering the undulator gaps
• Pump-probe repetition rate: 40Hz to 1KHz
• Detector readout rate: 10-100Hz with the new large area, high speed readout Rayonix detector (to be installed in March 2014)
• Focusing: 20 (v) X 20 (h) µm²

References

• Chen, J., Trigo, M., Fahy, S., Murray, E. D., Sheu, Y. M., Graber, T., Henning, R., Chien, Y. J., Uher, C., and Reis, D. A.  Time- and momentum-resolved probe of heat transport in photo-excited bismuth  Applied Physics Letters 102, 181903 (2013)
• Collet, E., Moisan, N., Baldé, C., Bertoni, R., Trzop, E., Laulhé, C., Lorenc, M., Servol, M., Cailleau, H., Tissot, A., Boillot, M.-L., Graber, T., Henning, R., Coppens, P., and Cointe, M. B.-L.  Ultrafast spin-state photoswitching in a crystal and slower consecutive processes investigated by femtosecond optical spectroscopy and picosecond X-ray diffraction.  Phys Chem Chem Phys 14, 6185–6192 (2012)
• Durbin, S. M., Clevenger, T., Graber, T., and Henning, R.  X-ray pump optical probe cross-correlation study of GaAs.  Nat Photon 6, 111–114 (2012)
• Graber, T., Anderson, S., Brewer, H., Chen, Y.-S., Cho, H. S., Dashdorj, N., Henning, R. W., Kosheleva, I., Macha, G., Meron, M., Pahl, R., Ren, Z., Ruan, S., Schotte, F., Šrajer, V., Viccaro, P. J., Westferro, F., Anfinrud, P., and Moffat, K.  BioCARS: a synchrotron resource for time-resolved X-ray science.  J Synchrotron Rad 18, 658–670 (2011)
• Makal, A., Benedict, J., Trzop, E., Sokolow, J., Fournier, B., Chen, Y., Kalinowski, J. A., Graber, T., Henning, R., and Coppens, P.  Restricted Photochemistry in the Molecular Solid State: Structural Changes on Photoexcitation of Cu(I) Phenanthroline Metal-to-Ligand Charge Transfer (MLCT) Complexes by Time-Resolved Diffraction.  J Phys Chem A 116, 3359–3365 (2012)