Their research allows double ionization events to be observed at the time scale of attoseconds, which are one-billionth of a billionth of a second. The physicists have also shown that these ionization events occur earlier than thought -- a key factor to improving knowledge of correlated electron dynamics, which involve two electrons and their interactions with each other. The work appears in a recent issue of Nature Communications.
"The research involves studying if these correlated electrons, ejected from an atom or a molecule, are traveling in the same or opposite directions," said Nora Johnson, a doctoral student in physics from Dell Rapids, S.D. "We can also determine if one electron has all the energy or if they share energy equally."
Other university researchers involved include Itzik Ben-Itzhak, university distinguished professor of physics, and Matthias Kling, assistant professor of physics. Kling is the principal investigator for the project and is on research leave at the Max Planck Institute of Quantum Optics in Garching, Germany, where he is performing related research. All of the researchers are involved with the university's James R. Macdonald Laboratory.
Double ionization occurs when two electrons are removed from an atom -- a process that can be caused by an intense laser pulse. When double ionization occurs in the laser field it can take the form of a sequential process, in which the laser removes one electron and then removes the other electron. This project focuses on another mechanism -- the nonsequential process for ionization -- in which the laser removes one electron, which is accelerated and hits a second electron to excite it. The laser then knocks out the second electron from the atom.
The researchers sent a four femtosecond-long laser pulse onto argon atoms. A femtosecond is a millionth of a billionth of a second. While most of the argon atoms were singly ionized, approximately every thousandth atom underwent nonsequential double ionization.
"The surprising result is that everybody expected that the second electron becomes excited and then, when the laser field is the strongest, this electron is removed," said Ben-Itzhak, director of the Macdonald laboratory. "But it actually happens earlier."
The researchers discovered that the time between the recollision and the second ionization is about 400 attoseconds. This is about 200 attoseconds earlier than the peak of the field, which is when physicists expected the second ionization to occur.
Johnson conducted her early experiments at the Macdonald Laboratory. She performed more extensive experiments during a 2009 Fulbright Fellowship at the Max Planck Institute of Quantum Optics. The two organizations have an ongoing collaboration and the Kansas State University team is directly funded by a $400,000 National Science Foundation grant.
"The key is that Nora has brought knowledge from Germany about short pulses and we can now continue these experiments in Kansas," Ben-Itzhak said. "We have an ongoing collaboration with them that goes both ways."
Now that the researchers have made an important discovery with atoms, Johnson is performing a similar experiment with molecules. She is performing experiments at the Macdonald Laboratory and will use the laboratory's expertise in imaging molecules.
"A molecule is more complex than an atom, which typically means its reaction dynamics are richer," Johnson said. "We are excited to pursue correlated electron dynamics at the next level of complexity to further understand them."
Itzik Ben-Itzhak | EurekAlert!
Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory
SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
27.04.2017 | Life Sciences
27.04.2017 | Physics and Astronomy
27.04.2017 | Earth Sciences