Ultrafast science studies processes in atoms, molecules, or materials that occur in millionths of a billion seconds or faster. This time scale is called femtoseconds, which is equivalent to 10-15 seconds. In addition to ultrafast science, researchers use short pulses of photons, electrons and ions to test matter. Femtosecond X-ray pulses can produce stop-motion images of how atoms move during molecular transformation or how they vibrate on thin film surfaces. This timeline allows scientists to explore details of how life-based processes change over time. For example, they can study how chemical bonds break and form and how excited electrons reshape the energy landscape of material transformation.
Newer tools can produce impulses lasting hundreds attoseconds (10-18 seconds). These even faster impulses allow scientists to monitor how electrons move when excited in chemical reactions.
Scientists monitored ultra-fast structural changes for the first time as ring-shaped gas molecules dissipated after light splitting them. The measurements were assembled in series as a basis for computer animations depicting molecular motion. Credits: Video courtesy of SLAC National Accelerator Laboratory
Ultrafast scientific experiments increase 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 studying these phenomena are gaining new insights on how to design materials with new properties and more efficient chemical processes.
Ultrafast scientific facts
- The development of X-ray-free lasers is a breakthrough for ultrafast science.
- Ahmed Zewail was awarded the Nobel Prize in Chemistry in 1999 for his invention of “femtochemistry”.
- In one femtosecond, light travels only 300 nanometers, a distance comparable to the size of a virus.
- A femtosecond is up to 1 second like 1 second is up to 30 million years.
- To date, the shortest X-ray laser pulses delivered by LCLS last 5 femtoseconds, approximately the same time it takes a molecule to lose an electron.
- Most ultrafast experiments involve the ability of optical lasers in a short time. These laser pulses can then be converted into other types of pulses. The result is that researchers can tailor experiments by selecting pulses from selected electromagnetic radiation energy (including X-rays) and electron-like particles.
- The most common form of ultrafast experiment involves “pumping” a pulse to excite the material under test, and after selecting an ultra-short time delay, a “trial” pulse to measure the feature in the sample. Scientists are changing the time delay and measuring the history of the excited state as the system returns to equilibrium. The pump and probe can be different types of pulses, depending on the type of excitation desired and the type of property being measured.
DOE Office of Science: Contributions to Ultrafast Science
The DOE Office of Science, the Office of Basic Energy Sciences (BES), invests in basic research and user facilities for ultrafast science. This research includes fundamental research into changes in the electronic structure of materials and the flow of energy in new materials and chemical systems. The Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory is a cutting-edge facility for ultrafast scientific research. LCLS was the first hard electron-free hard X-ray laser in the world. It uses strong flashes of X-rays – every 5 femtoseconds and a billion times brighter than previously available – to take atomic images. LCLS will be even stronger when SLAC finishes working on the upgraded LCLS-II. Researchers put them together to create films about chemical and physical processes. An insight into these fundamental, ultra-fast movements could help solve some of the mysteries of the natural world and support the development of innovative materials, energy solutions, medicines and more.