Two separate research fields have been united in Hamburg for the very first time. Ultrashort laser pulses enable us to observe and manipulate matter on very short time scales, whereas ultracold atoms permit experiments with high precision and controllability. In the cluster of excellence “The Hamburg Centre for Ultrafast Imaging,” scientists from Universität Hamburg have united the two research fields and succeeded in observing the emergence of ions in ultracold atoms. Their findings have been published in the new scientific journal Communications Physics.
More than a century ago, Albert Einstein published his theoretical work on the photo-effect, which fundamentally describes the photoionization of matter, or the process of dissolving electrons from atoms by using light. This discovery earned him a Nobel Prize in 1921.
However, it turns out that the process is very complicated in detail. Up until now it has been nigh impossible to carry out experimental measurements of the absolute ionization probability, e.g., the percentage of atoms ionized after light irradiation.
The teams of scientists led by Prof. Dr. Markus Drescher and Prof. Dr. Klaus Sengstock have uniquely combined expertise in ultracold atoms with phenomena of ultrafast physics, which has opened up a fundamentally new experimental approach.
Ultrashort laser pulses can be so intense that they rip atoms apart. This process is called strong-field ionization and the details depend on the energy and color of the laser light. Up until now, it was not always possible to know which ionization regime dominates. The scientists have now succeeded in observing this in detail by using ultracold atoms. As there is hardly any atomic motion after the ionization process, it is possible to accurately measure the regimes.
The scientists used laser light to cool rubidium atoms to ultracold temperatures of 100 nanokelvins, only slightly above absolute zero temperature of -273.15° Celsius. An intense ultrashort laser pulse illuminated parts of the cloud of rubidium atoms for a very short time of 215 femtoseconds (a femtosecond is one millionth of one billionth of a second) and ionized a fraction of the atoms. The remaining atomic density was imaged onto a camera so that the amount of ionized atoms could be accurately measured.
In particular, the scientists observed that the atomic bond in an optical light field is modified so fast that the atomic shell cannot follow the oscillation of the light field. During ionization the atom thus absorbs multiple light particles (photons) simultaneously.
“The presented work paves the way towards further experiments using ultrashort laser pulses for creating ions and electrons in ultracold atomic samples,” lead author Philipp Wessels from Prof. Sengstock’s group explains.
“This leads to precise measurements of ultrafast processes by using ultracold atoms, because these systems can be controlled extremely well experimentally.” The results can also be used to help realize quantum computers based on ultracold ions. Such computers may solve certain problems faster than conventional ones.
Parallel to these experiments, an international collaboration with Prof. Nikolay Kabachnik (Moscow State University) and Prof. Andrey Kazansky (Ikerbasque, Spain) calculated the ionization process theoretically. The scientists modelled the quantum mechanical interaction between atom and laser field, with the following result: the theoretical predictions are in perfect agreement with the measured data.
P. Wessels, B. Ruff, T. Kroker, A. K. Kazansky,
N. M. Kabachnik, K. Sengstock, M. Drescher, and J. Simonet,
"Absolute strong-field ionization probabilities of ultracold rubidium atoms,"
Accepted in Communications Physics (new journal of the Nature group).
Link to the Journal: https://www.nature.com/commsphys/
Birgit Kruse | idw - Informationsdienst Wissenschaft
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences