Ultrafast and Intense Multispectral Light Tools for Control of Few-Body Material Dynamics
Speaker: Jeffrey Moses, MIT
Department: Mechanical & Aerospace Engineering
Location: Engineering Quadrangle J223
Date/Time: Monday, February 25, 2013, 12:30 p.m. - 1:30 p.m.
Enacting change in a dynamical system requires an impulse or a modification of boundary conditions. For real-time control of a system, we require those impulses or changes to be on the natural timescale of its dynamics. This poses a challenge to scientists and engineers whose mechanical systems are the microscopic particles and quasi-particles of materials, since these can exhibit very fast dynamics. The fastest dynamics in materials, including molecular rotations, the vibrations of nuclei, and the motion of electrons, occur from picosecond (10-12 sec.) timescales down to attoseconds (10-18 sec.) For example, the atomic unit of time one radian of the Bohr electrons orbital cycle lasts only 24 x 10-18 seconds.
The fastest impulses and varying potentials we can make and control in a laboratory are light pulses. As engineers of material dynamics or physicists aiming to understand the essential dynamical relationships of a system, our goal is to trigger changes and then capture them. This involves making light pulses of the appropriate colors for enacting and capturing change X-ray, ultraviolet, visible, near-IR, mid-IR, THz, etc. synchronizing them, amplifying them, shaping them, and making them as short as possible. Such tools hold the promise of sequential, coherent, and selective activation of such properties as the valence electron, core electron, vibrational, and rotational configurations of materials, thus enabling a choreography of correlated multi-body dynamics in real time. I will review some of the most recently developed light pulse tools including single-cycle-duration light-pulse synthesizers, attosecond pulses, and energetic, ultrabroadband, mid-infrared waves and our aim to use them to benchmark a basic scheme for control of molecular dissociation carried out by tuning the phase between synchronized vibrational and optical oscillations in H2+. Possible applications in other settings, covering electronic dynamics in atoms, molecules, surfaces, and nanostructures, will be discussed briefly.