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Attosecond Physics

Attosecond Physics. Ultrafast Physics at a new Frontier. Dawn Fraser University of Ottawa, Dec 2005. Flash Photography and Film. Application on molecular and atomic scale ??. Can we take pictures of electrons or make movies of molecular vibration?.

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Attosecond Physics

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  1. Attosecond Physics Ultrafast Physics at a new Frontier Dawn Fraser University of Ottawa, Dec 2005

  2. Flash Photography and Film Application on molecular and atomic scale ?? Can we take pictures of electrons or make movies of molecular vibration? • For a camera to “freeze” the motion of an object: • the wavelength of the light must be shorter than the extension of the subject • the duration of the light flash must be short relative to the speed of the subject

  3. Just how fast is ultrafast? A classical electron makes one Bohr orbit in ~150 attoseconds. To make movies of molecular and atomic processes we need pulses with: Spatial resolution: Angstrom (10^-10)m Temporal resolution: < Femtosecond (10^-15)s • Right now: • Spatial needs met by electron microscopes, Synchroton X-ray sources • Temporal needs met by lasers • No one source can yet meet both needs

  4. The Femtosecond Barrier Historical progress of ultra-short laser technology shows evidence of a femtosecond barrier Natural limit due to pulse limitations in the visible range Lead to the introduction of ‘High-Order Harmonics”

  5. High-Order Harmonic Generation Produces pulses in the extreme ultra-violet regime (XUV) Three step recombination model (1) Laser “driver” induced tunneling (2) Electron trajectory under EM field (3) Recombination with parent ion Generates a train of attosecond pulses

  6. The Trouble was… In order to meet the goals of attosecond physics, they needed to isolate a single attosecond pulse! • Short driver pulse • Control of the carrier-envelope phase Advances resulted in a single neat XUV pulse “Streak Camera” determined that single pulses had been localized to a time scale of <250as !!

  7. How is this being applied? Well… maybe don’t grab the popcorn just yet. Attosecond pulses first used to probe Auger decay in krypton gas • Electrons emitted at different times will receive different energies • Time differences can be inferred • Limitations: • Laser intensity • Optical tools • Interpretation of data • Wavelength barrier?

  8. The Future Free Electron Laser: • Electrons in HHG have attosecond duration • Consecutive ‘snapshots’ can be taken - <1fs timescale • Application of HHG to molecules can provide spatial information about electrons in the valence orbital!! • What might be next? • Septosecond physics??

  9. References Agostini P and L. F. DiMauro, The Physics of Attosecond Light Pulses, Rep. Prog. Phys. 67: 813-855, 2004 Brabec T, New Science at the Ultrafast Frontier, Physics World, 2004 Hellemans A, In the Blink of an Eye, Science, 306:1313, 2004 Lewenstein M, Resolving Physical Processes on the Attosecond Time Scale, Science, 297:1131, 2002 Silberberg Y, Physics at the Attosecond Frontier, Nature, 414: 494-495, 2001

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