Amid a fast game in a vast venue, sports photography seeks to freeze motion and isolate small portions of space for special consideration. In the scientific world of the ultrafast and ultrasmall, stroboscopic effects are achieved with greatly attenuated laser pulses. The advent of laser light served up in femtosecond (or 10^-15 second) bursts has helped to elucidate the molecular world by freezing their vibrational and rotational motions. Scientists would of course like to instigate and monitor even shorter times and distances.
A collaboration between scientists at the Technical University of Vienna and the Max Planck Institute for Quantum Optics (MPQ) has now done precisely this. They have produced a series of 2.5-fsec pulses, each consisting of only a few cycles of a carrier light signal modulated within an amplitude envelope. In the case of the Vienna-MPQ experiment, however, all the pulses are identical (a feat not achieved previously) and the phase of the carrier wave within the envelope is controlled with a time resolution of about 100 attoseconds.
When the intense (100 GW) few-cycle pulse strikes an atom, an electron can be stripped away quickly, and reabsorbed just as quickly. This violent excursion results in the emission of a sharp x-ray spike with a duration even shorter than the pulse that excited the reaction. In fact the x-ray pulses are about 500 attoseconds long. Moreover, because all the waveforms of the optical pulse are identical, and controlled, the subsequent electron motions and x-ray emissions are also highly controlled and reproducible. At a talk at this weeks meeting of the American Association for the Advancement of Science (AAAS) in Denver, Vienna physicist Ferenc Krausz said that this sub-femtosecond control of electron currents represented true attophysics, a new technique for directing and watching atomic processes at unprecedentedly short time intervals. (See Baltuska et al., Nature, 6 February 2003.)
Phillip F. Schewe | PHYSICS NEWS UPDATE
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Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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