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Electrons caught in the act of tunnelling
We have to climb a mountain in order to conquer it. In quantum physics there is a different way: objects can reach the opposite side of a hill simply by tunnelling through it, instead of laboriously climbing over it. An international team of researchers working with Prof. Ferenc Krausz from the Max Planck Institute for Quantum Optics has now observed electrons in this tunnelling process.
This effect is responsible for the ionization of atoms under the influence of strong magnetic fields. The electrons overcome the attraction of the atomic nucleus by tunnelling through a potential wall. The scientists used ultra-short laser pulses to show discrete stages of ionization in this process, each of which lasts 100 attoseconds - a fraction of a billionth of a second. The results make a significant contribution to understanding how electrons move around in atoms and molecules.
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Krausz and his colleagues have now followed this process live with the aid of two light pulses: an intense pulse of just a few wave trains of red laser light and an attosecond pulse of extreme ultraviolet light perfectly synchronized with the red pulse. The electrical field of the laser pulses periodically exerts strong forces on the electrons. When the force is at its strongest, the light force presses the potential wall downwards. For a short moment when the wave peaks, the electron has the opportunity to penetrate the barrier and escape from the atom. This opportunity only arises when the wave peaks, that is over an extremely short interval of a fraction of a femtosecond, a trillionth of a second.
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"The experiments not only provide us with insight into the dynamics of electron tunnelling for the first time," says Krausz. "We have also shown that the movement of electrons in atoms or molecules can be observed in real time with the aid of laser field-induced tunnelling." Based on this finding and the enabled control over electron movement within the atom, in the future scientists will be able to research how the boundaries of microelectronics can be shifted, or how to develop sources of compact, very bright X-rays. These will in turn allow progress to be made in the imaging of biological objects and in radiation therapy.
We have to climb a mountain in order to conquer it. In quantum physics there is a different way: objects can reach the opposite side of a hill simply by tunnelling through it, instead of laboriously climbing over it. An international team of researchers working with Prof. Ferenc Krausz from the Max Planck Institute for Quantum Optics has now observed electrons in this tunnelling process.
This effect is responsible for the ionization of atoms under the influence of strong magnetic fields. The electrons overcome the attraction of the atomic nucleus by tunnelling through a potential wall. The scientists used ultra-short laser pulses to show discrete stages of ionization in this process, each of which lasts 100 attoseconds - a fraction of a billionth of a second. The results make a significant contribution to understanding how electrons move around in atoms and molecules.
>
Krausz and his colleagues have now followed this process live with the aid of two light pulses: an intense pulse of just a few wave trains of red laser light and an attosecond pulse of extreme ultraviolet light perfectly synchronized with the red pulse. The electrical field of the laser pulses periodically exerts strong forces on the electrons. When the force is at its strongest, the light force presses the potential wall downwards. For a short moment when the wave peaks, the electron has the opportunity to penetrate the barrier and escape from the atom. This opportunity only arises when the wave peaks, that is over an extremely short interval of a fraction of a femtosecond, a trillionth of a second.
>
"The experiments not only provide us with insight into the dynamics of electron tunnelling for the first time," says Krausz. "We have also shown that the movement of electrons in atoms or molecules can be observed in real time with the aid of laser field-induced tunnelling." Based on this finding and the enabled control over electron movement within the atom, in the future scientists will be able to research how the boundaries of microelectronics can be shifted, or how to develop sources of compact, very bright X-rays. These will in turn allow progress to be made in the imaging of biological objects and in radiation therapy.