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The research team lead by Kelly Gaffney uses femtosecond duration pulses of light ranging from hard x-ray to mid-IR wavelengths to study atomic and electronic dynamics in condensed matter. The femtosecond to many picoseconds time scale for the motion of atoms and molecules -- the translations, rotations, and vibrations -- necessitates the use of ultrashort pulses to resolve these motions in the time domain.
Resolving these motions in the time domain provides access to the pathways followed during the chemical and physical transformations of materials. In these studies we use a pulse of laser light to initiate a process, be it a chemical reaction in solution, a solid-liquid phase transition in a crystal, or photocurrent generation in a solar cell. We then use subsequent pulses of light to characterize the light initiated transformation. By utilizing a variety of wavelengths to probe the transformation we can access different aspects of the mechanism. We can probe electronic degrees of freedom with visible, UV, and x-ray spectroscopy, we can probe vibrational degrees of freedom with vibrational spectroscopy in the mid-IR, and we can use hard x-ray diffraction to probe atomic and molecular structure. All these methods complement one another and the diversity of scattering and spectroscopic techniques used to probe transient phenomena often proves essential to understanding the complex dynamics of condensed matter systems. Within this general framework we have a series of specific projects currently in development.
Publications:
Making Molecular Movies: 10,000,000,000,000 Frames per Second
SLAC Public Lecture December 2006
Ultrafast Dynamics of Laser-Excited Solids:
D.A. Reis, K.J. Gaffney, G.H. Gilmer, D. Torralva, Mat. Res. Soc. Bull. 31, 1 (2006).
A.M. Lindenberg et al., 'Atomic-Scale Visualization of Inertial Dynamics',
Science, 308, 392 (2005)
Observation of Structural Anisotropy and the Onset of Liquid-like Motion During the Nonthermal melting of InSb:
K.J. Gaffney, et al., Phys. Rev. Lett. 95, 125701 (2005).
Following a Structural Phase Transition in Real Time with Atomic Spatial Resolution:
SSRL Science Highlight November 2005
People:
Anniruddha Deb
Kelly Gaffney
Pat Hillyard
Jen Kaspar
Drew Meyer
Sungnam Park