Capturing Surface Processes Chris Nicklin Science 343, 739 (2014); DOI: 10.1126/science.1250472
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Science (print ISSN 0036-8075; online ISSN 1095-9203) is published weekly, except the last week in December, by the American Association for the Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005. Copyright 2014 by the American Association for the Advancement of Science; all rights reserved. The title Science is a registered trademark of AAAS.
Downloaded from www.sciencemag.org on February 13, 2014
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PERSPECTIVES References and Notes 1. J. Sheffield et al., Nature 491, 435 (2012). 2. IPCC, Summary for Policymakers, in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge Univ. Press, Cambridge and New York, 2013). 3. C. Prudhomme et al., Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1222473110 (2014). 4. J. Schewe et al., Proc. Natl. Acad. Sci. U.S.A. 10.1073/ pnas.1222460110 (2014). 5. S. Feng, Q. Fu, Atmos. Chem. Phys. 13, 10081 (2013). 6. A. Dai, Nat. Clim. Change 3, 52 (2013). 7. M. M. Joshi et al., Clim. Dyn. 30, 455 (2008). 8. M. P. Byrne, P. A. O’Gorman, J. Clim. 26, 4000 (2013).
9. A. Dai, J. Clim. 19, 3589 (2006). 10. A. J. Simmons, K. M. Willett, P. D. Jones, P. W. Thorne, D. P. Dee, J. Geophys. Res. 115, D01110 (2010). 11. D. P. Rowell, R. G. Jones, Clim. Dyn. 27, 281 (2006). 12. P. A. O’Gorman, C. J. Muller, Environ. Res. Lett. 5, 025207 (2010). 13. M. Collins et al., in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge Univ. Press, Cambridge and New York, 2013), chap. 12. 14. J. Scheff, D. M. W. Frierson, J. Clim. 10.1175/ JCLI-D-13-00233.1 (2013). 15. S. I. Seneviratne et al., Geophys. Res. Lett. 40, 5212 (2013).
16. K. E. Trenberth, Clim. Res. 47, 123 (2011).
Acknowledgments: This Perspective germinated at the Bert Bolin Centre 2013 Summer School on Subtropical Climate. We acknowledge the support of the National Basic Research Program of China (2012CB955303), the National Natural Science Foundation of China (grant 41275070), and the Australian Research Council Centre of Excellence for Climate System Science.
Supplementary Materials www.sciencemag.org/content/343/6172/737/suppl/DC1 Fig. S1 References 10.1126/science.1247620
CHEMISTRY
A modified surface x-ray diffraction geometry allows dynamic restructuring of surfaces to be studied.
Capturing Surface Processes Chris Nicklin
T
he outer atomic layers of a solid or liquid play a central role in determining the properties of the sample as a whole, because it is here where the material interacts with the external environment. Detailed knowledge of the arrangement of atoms at a surface or interface between two materials is required to understand and tune the material’s properties. This outer-layer structure is crucial for technological processes such as catalysis, lubrication, and electron transport. In surface x-ray diffraction, surface structures are investigated by directing high-energy x-rays at a sample at grazing angles of typically less than 1° (1). On page 758 of this issue, Gustafson et al. outline a different geometry for these measurements, using even higher-energy x-rays and shallower angles to allow faster data collection, enabling dynamic surface restructuring processes to be captured (2). In surface x-ray diffraction, the diffracted intensity results from a combination of x-rays scattered from the bulk of the sample and x-rays scattered from its surface (see the figure). Intense Bragg peaks occur where the bulk scattering exhibits constructive interference. The truncation of the sample at the surface leads to streaking between the Bragg peaks in the direction perpendicular to the surface. These streaks, known as crystal truncation rods (CTRs) (3) show modulations in intensity that results from interference between the bulk-scattered and surface scattered x-rays. Additionally, ordered reconstructions of
the outer atomic layers result in superstructure rods, which have an intensity profile that depends only on the surface scattering. Modeling these modulations can reveal the surface structure and registry with the bulk with a resolution of
If you wish to distribute this article to others, you can order high-quality copies for your colleagues, clients, or customers by clicking here. Permission to republish or repurpose articles or portions of articles can be obtained by following the guidelines here. The following resources related to this article are available online at www.sciencemag.org (this information is current as of February 13, 2014 ): Updated information and services, including high-resolution figures, can be found in the online version of this article at: http://www.sciencemag.org/content/343/6172/739.full.html A list of selected additional articles on the Science Web sites related to this article can be found at: http://www.sciencemag.org/content/343/6172/739.full.html#related
Science (print ISSN 0036-8075; online ISSN 1095-9203) is published weekly, except the last week in December, by the American Association for the Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005. Copyright 2014 by the American Association for the Advancement of Science; all rights reserved. The title Science is a registered trademark of AAAS.
Downloaded from www.sciencemag.org on February 13, 2014
This copy is for your personal, non-commercial use only.
PERSPECTIVES References and Notes 1. J. Sheffield et al., Nature 491, 435 (2012). 2. IPCC, Summary for Policymakers, in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge Univ. Press, Cambridge and New York, 2013). 3. C. Prudhomme et al., Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1222473110 (2014). 4. J. Schewe et al., Proc. Natl. Acad. Sci. U.S.A. 10.1073/ pnas.1222460110 (2014). 5. S. Feng, Q. Fu, Atmos. Chem. Phys. 13, 10081 (2013). 6. A. Dai, Nat. Clim. Change 3, 52 (2013). 7. M. M. Joshi et al., Clim. Dyn. 30, 455 (2008). 8. M. P. Byrne, P. A. O’Gorman, J. Clim. 26, 4000 (2013).
9. A. Dai, J. Clim. 19, 3589 (2006). 10. A. J. Simmons, K. M. Willett, P. D. Jones, P. W. Thorne, D. P. Dee, J. Geophys. Res. 115, D01110 (2010). 11. D. P. Rowell, R. G. Jones, Clim. Dyn. 27, 281 (2006). 12. P. A. O’Gorman, C. J. Muller, Environ. Res. Lett. 5, 025207 (2010). 13. M. Collins et al., in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge Univ. Press, Cambridge and New York, 2013), chap. 12. 14. J. Scheff, D. M. W. Frierson, J. Clim. 10.1175/ JCLI-D-13-00233.1 (2013). 15. S. I. Seneviratne et al., Geophys. Res. Lett. 40, 5212 (2013).
16. K. E. Trenberth, Clim. Res. 47, 123 (2011).
Acknowledgments: This Perspective germinated at the Bert Bolin Centre 2013 Summer School on Subtropical Climate. We acknowledge the support of the National Basic Research Program of China (2012CB955303), the National Natural Science Foundation of China (grant 41275070), and the Australian Research Council Centre of Excellence for Climate System Science.
Supplementary Materials www.sciencemag.org/content/343/6172/737/suppl/DC1 Fig. S1 References 10.1126/science.1247620
CHEMISTRY
A modified surface x-ray diffraction geometry allows dynamic restructuring of surfaces to be studied.
Capturing Surface Processes Chris Nicklin
T
he outer atomic layers of a solid or liquid play a central role in determining the properties of the sample as a whole, because it is here where the material interacts with the external environment. Detailed knowledge of the arrangement of atoms at a surface or interface between two materials is required to understand and tune the material’s properties. This outer-layer structure is crucial for technological processes such as catalysis, lubrication, and electron transport. In surface x-ray diffraction, surface structures are investigated by directing high-energy x-rays at a sample at grazing angles of typically less than 1° (1). On page 758 of this issue, Gustafson et al. outline a different geometry for these measurements, using even higher-energy x-rays and shallower angles to allow faster data collection, enabling dynamic surface restructuring processes to be captured (2). In surface x-ray diffraction, the diffracted intensity results from a combination of x-rays scattered from the bulk of the sample and x-rays scattered from its surface (see the figure). Intense Bragg peaks occur where the bulk scattering exhibits constructive interference. The truncation of the sample at the surface leads to streaking between the Bragg peaks in the direction perpendicular to the surface. These streaks, known as crystal truncation rods (CTRs) (3) show modulations in intensity that results from interference between the bulk-scattered and surface scattered x-rays. Additionally, ordered reconstructions of
the outer atomic layers result in superstructure rods, which have an intensity profile that depends only on the surface scattering. Modeling these modulations can reveal the surface structure and registry with the bulk with a resolution of
