An international team of scientists based in Regensburg, Germany, has now recorded the ultrafast motion of a single molecule directly in time and space by combining a femtosecond laser with an atomic resolution microscope.
Atoms and molecules are the constituents of virtually all matter that surrounds us. Interacting with each other while following the rules of nature, they form complex systems ranging from modern technology to living creatures. Their behavior, that is, what they actually do, basically determines all of natural and life sciences.
They are so small, however, that we cannot observe them in daily life. Even with the best optical microscopes, atoms and molecules are a thousand times too small to be seen; the microscope would have to see down to the ångström scale (1 ångström = 0.0000000001 m). Yet, we would be able to solve innumerable vital problems if we could just view the microcosm directly and watch the elementary constituents of matter at work.
Only a few decades ago, imaging individual steady atoms became possible thanks to the invention of sophisticated types of microscopes that are not based on optics. But even in apparently stationary massive bodies, the individual atoms and molecules are actually not steady, but in a state of constant motion. They speed amongst their neighbors in random directions while vibrating and rotating vigorously.
And although we can imagine (and calculate) this rocking, rolling and shaking motion, it occurs unbelievably rapidly, taking only a few femtoseconds (one millionth of a billionth of a second, i.e. 0.000000000000001 s), which is way too fast to be resolved by any atomic microscope.
Consequently, even though the question of how individual atoms and molecules behave is at the heart of all fields of natural science, until recently, nobody had ever seen a single molecule move on its intrinsic ultrafast timescale. In order to literally watch their motion, one would need a microscope many billions of times more rapid than the fastest high-speed cameras, which has until now remained way out of reach.
An international team of scientists based in Regensburg, Germany, has now tackled this challenge. Their aim was to revolutionize the way in which researchers look at the nanoworld: advancing from images to moving images of molecules. To do so, they developed an unprecedented ultrafast microscope. They combined the most powerful tool researchers have to access ultrafast time scales, femtosecond laser pulses, with highly advanced scanning tunneling microscopy capable of imaging individual molecules. The principle of this microscopy technique is similar to a record player.
A sharp needle is moved across a surface to reveal its relief. But in scanning tunneling microscopy, the tip of this needle is as sharp as a single atom. Also, it does not touch the surface, but hovers over it while electrons move between the tip and surface thanks to a quantum mechanical effect called tunneling. As a result, the tip serves as a probe that is sensitive to corrugation smaller than a single molecule.
The researchers in Regensburg developed a novel scheme by controlling the tunneling process by ultrafast light pulses so short that each pulse only contained one single oscillation cycle of the lightwave. This mechanism gives them total quantum control over a select electron within a single molecule with simultaneous femtosecond temporal and sub-ångström spatial precision. As a result, they realized a microscope that not only allows them to image individual molecules, but also to “see” them move on their intrinsic time scale.
With this unique expertise, the researchers could – for the first time – record femtosecond snapshot images of a single molecule, directly resolved in space and time. Even more, they could set the molecule in motion and watch its ultrafast response. For this, they used two light pulses. The first stimulated an electron tunneling event, giving the molecule a kick that set it in motion, such that it began to vibrate atop the surface.
The second pulse arrived at the molecule a very short time later and attempted to drive a second tunneling event. Crucially, its ability to do so depended on the instantaneous position of the molecule in its vibrational motion. The researchers then repeated this scenario, while tracking the ability of the second pulse to drive electron tunneling, for a series of delay times between the first and second pulses. What resulted was a direct measurement of the molecule’s ultrafast motion in space and time – an oscillation with a period faster than a trillionth of a second – in the first-ever femtosecond single-molecule movie!
This development finally opens the door to exploring the mystery of the ultrafast microcosm that had previously been obscured. Accessing the nanoworld with all its intriguing facets in this unprecedented way is expected to reveal key steps in chemistry and biology, and inspire future technologies based on single-molecule devices and lightwave-driven electronics.
Publication: DOI: 10.1038/nature19816
Contact for media representatives:
Prof. Dr. Rupert Huber
Lehrstuhl für Experimentelle und Angewandte Physik
Tel.: 0941 943-2070
Prof. Dr. Jascha Repp
Professur für Experimentelle und Angewandte Physik
Tel.: 0941 943-4201
Claudia Kulke | idw - Informationsdienst Wissenschaft
Sharpening the X-ray view of the nanocosm
23.03.2018 | Changchun Institute of Optics, Fine Mechanics and Physics
Drug or duplicate?
23.03.2018 | Fraunhofer-Institut für Angewandte Festkörperphysik IAF
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy