Ultrafast science is the study of processes in atoms, molecules, or materials that occur in millionths of a billionth of a second or faster. This time scale is called femtoseconds, which equals 10-15 seconds. With superfast science, researchers use short pulses of photons, electrons and ions to probe matter. Femtosecond X-ray pulses can produce stop-motion images of how atoms move during molecular transformations or how they vibrate on thin film surfaces. This time scale allows scientists to study the details of how the fundamental processes of life change over time. For example, they can study how chemical bonds break and form and how excited electrons reshape the energy landscape of material transformations.
The new tools can produce pulses lasting hundreds of attoseconds (ten-18 seconds). These even faster pulses allow scientists to track the movement of electrons as they are excited in chemical reactions.
Scientists have for the first time tracked lightning-fast structural changes as ring-shaped gas molecules unravel after being cracked open by light. The measurements were compiled in sequence as the basis for computer animations showing molecular motion. Credit: Video courtesy of SLAC National Accelerator Laboratory
Ultra-fast science experiments improve our understanding of how atomic, electronic and magnetic structures move and change on fundamental time scales. They also help us relate these results to materials and chemical properties. Scientists who study these phenomena gain new insights into how to design materials with new properties and more efficient chemical processes.
Lightning Fast Science Facts
- The development of X-ray free electron lasers is a breakthrough for ultrafast science.
- Ahmed Zewail was awarded the 1999 Nobel Prize in Chemistry for inventing “femtochemistry”.
- In a femtosecond, light travels barely 300 nanometers, a distance comparable to the size of a virus.
- A femtosecond is to 1 second as 1 second is to 30 million years.
- To date, the shortest X-ray laser pulses delivered by LCLS last 5 femtoseconds, roughly the same time it takes for a molecule to lose an electron.
- Most ultrafast experiments involve the narrow temporal pulsing capability of optical lasers. These laser pulses can then be converted into other types of pulses. The result is that researchers can tailor their experiments by choosing pulses from a selection of electromagnetic radiation energy (including X-rays) and particles such as electrons.
- The most common form of ultrafast experiment involves a “pump” pulse to excite the material to be studied, and after a selected ultra-short delay, a “probe” pulse to measure a characteristic of the sample. Scientists vary the delay and measure the excited state history as the system returns to equilibrium. The pump and the probe can be of different types of pulses, depending on the type of excitation sought and the type of property to be measured.
DOE Office of Science: Contributions to superfast science
The DOE Office of Science, Office of Basic Energy Sciences (BES) invests in basic research and user facilities for ultrafast science. This research includes fundamental studies of changes in the electronic structure of materials and energy flow in new materials and chemical systems. The Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory is a premier facility for ultrafast scientific research. The LCLS was the world’s first free-electron hard X-ray laser. It uses powerful flashes of X-ray light – each as short as 5 femtoseconds and a billion times brighter than those previously available – to take atomic snapshots. The LCLS will be even more powerful when SLAC completes work on the improved LCLS-II. Researchers combine them to create movies of chemical and physical processes. Insights into these fundamental ultrafast movements could help solve some of the mysteries of the natural world and support the development of innovative materials, energy solutions, medicines, and more.
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