Ultrafast electron crystallography: Transient structures of molecules, surfaces, and phase transitions

• DOI: 10.1073/pnas.0307302101
• Publication Date: 2004-02-03T17:47:24Z
• Authors: Chong-Yu Ruan; Franco Vigliotti; Vladimir A. Lobastov; Songye Chen; Ahmed H. Zewail
• Keywords: Electron crystallography; Ultrafast electron diffraction

The static structure of macromolecular assemblies can be mapped out with atomic-scale resolution by using electron diffraction and microscopy crystals. For transient nonequilibrium structures, which are critical to the understanding dynamics mechanisms, both spatial temporal resolutions required; shortest scales length (0.1–1 nm) time (10 –13 10 –12 s) represent quantum limit, nonstatistical regime rates. Here, we report development ultrafast crystallography for direct determination structures submonolayer sensitivity. In these experiments, use crystalline silicon as a template different adsorbates: hydrogen, chlorine, trifluoroiodomethane. We observe coherent restructuring surface layers subangstrom displacement atoms after heat impulse. This dynamics, is monitored in steps 2 ps (total change ≤10 ps), contrasts that nanometer substrate. effect adsorbates phase transition at higher fluences were also studied through evolution streaks interferences, Bragg spots (and their rocking curves), rings patterns. compare results kinematical theory those x-ray developed study bulk behaviors. sensitivity achieved here, 6 orders magnitude larger cross section than diffraction, capabilities combined (≈0.01 Å) (300–600 fs) resolutions, promise diverse applications this tabletop methodology.