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

2. 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 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 Application on molecular and atomic scale ?? Flash Photography and Film Can we take pictures of electrons or make movies of molecular vibration?

3. 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 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 To make movies of molecular and atomic processes we need pulses with: Spatial resolution: Angstrom (10^-10)m Temporal resolution: < Femtosecond (10^- 15)s To make movies of molecular and atomic processes we need pulses with: Spatial resolution: Angstrom (10^-10)m Temporal resolution: < Femtosecond (10^- 15)s Just how fast is ultrafast? A classical electron makes one Bohr orbit in ~150 attoseconds.

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

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

6. In order to meet the goals of attosecond physics, they needed to isolate a single attosecond pulse! The Trouble was… Short driver pulse Control of the carrier-envelope phase 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. Well… maybe don’t grab the popcorn just yet. How is this being applied? 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 Electrons emitted at different times will receive different energies Time differences can be inferred Limitations: Laser intensity Optical tools Limitations: Laser intensity Optical tools Interpretation of data Wavelength barrier? Interpretation of data Wavelength barrier?

8. Free Electron Laser: The Future 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!! 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?? 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 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