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Attosecond Science Research at JASLab

Advanced laser technology, some of it developed in SIMS, is dramatically extending our control over almost all aspects of light and through it our ability to observe and control matter. The current state-of-the-art is:

Colour: How molecules respond to light of different colours is their "fingerprint". Each molecule reacts differently to a given colour. With laser technology we can define colours incredible accurately --- to one part in ~ 1015. There are about 1,000,000,000,000,000 distinct colours that can form a molecular fingerprint.

Time: Atoms and molecules are in constant motion. Reactions between them, involving fast electronic and vibrational motion power chemical and biological processes. Laser technology produces optical or electron pulses that are only 200 attoseconds (200/1,000,000,000,000,000,000 sec.) in duration. Ultrafast lasers allow us to measure the dynamics of many chemical reactions.

Intensity: Light is a wave of electric force. Electrical forces also hold electrons to ions in atoms and molecules or atoms together in molecules or solids. The forces exerted by lasers can approach or exceed the binding forces. Through these forces we have one important avenues for controlling the quantum world.
Wavelength: On the molecular scale, laser wavelengths are very large. Until recently that has meant that lasers could not "see" molecules. Now, laser wavelengths are approaching molecular dimensions and lasers control electrons are already less than molecular sizes. We are poised to revolutionize how we determine molecular structure.

Phase: Phase is what distinguishes quantum and classical mechanics. Because of their short duration, femtosecond duration pulses contain a broad bandwidth of phased radiation. Quantum interference offers a second avenue for controlling quantum systems.

Attosecond Science: Lasers were discovered in 1960. They allow us to control light. Lasers ensure that modern science is as revolutionary as it was 100 years ago. Lasers allow us to:

  • Produce very short light pulses (currently ~ 200 attoseconds). With short light pulses we can measure the very fastest processes in atoms, molecules and solids.
  • Produce very intense light pulses. Through them we control atoms and molecules.
  • Produce very narrow linewidth light beams. Through them we extend the precision spectroscopy from
  • Make phase controlled pulses.

Our research builds on a century old foundation. Nearly a century ago, quantum mechanics was developed to describe experiments on light-atom interactions. Fifty years ago the structures of small molecules were determined from studying how light interacts with them. Much of that research was done at NRC in the 1950's. This field of research was named spectroscopy. Now science is determining the structure of large molecules by how X-rays scatter from them.

The Attosecond and Strong Fields Science Project
The Attosecond and Strong Field Science project aims to exploit the extreme non-linear optics that strong laser fields permit. Since the non-linear physics is less well understood in this project, part of the project is concerned with extreme non-linear optics. It allows us to push to shorter pulses than with any other technology. However intense fields are also powerful tools for control. Control and extreme dynamics provides a strong link between the projects.

Intense laser pulses apply forces to the charged components of atoms, molecules or solids. If they exceed the forces holding the electron to its ion, then ionization occurs. Since the forces are large, in the continuum, the electron responds to the field almost classically. Controlling the laser field coherently controls the ionized electrons.

Even if the field is insufficient to ionize, the field cannot be ignored. It mixes and shifts all levels. Since we control the field, we exercise a strong degree of control over the photoelectron spectrum. In molecules, this gives us a tool to probe and control the molecule.