Authors: George Rajna
Catalysts are at the heart of fuel cells-devices that convert hydrogen and oxygen to water and enough electricity to power vehicles for hundreds of miles. But finding effective, inexpensive catalysts has been a key challenge to getting more of these hydrogen-powered, emission-free vehicles out on the road.  Multiple theoretical models have been developed to explain the relaxation dynamics of materials that form glasses. One such model is the dynamic facilitation theory, which predicts that the dynamics of systems are heterogeneous and relaxation displays parabolic behavior.  A glass is a curious material in between liquid and solid states of matter, but eventually glass always yields to its solid proclivity by settling into the ordered patterns of a crystal. Or so it was thought.  A new technique developed by MIT researchers reveals the inner details of photonic crystals, synthetic materials whose exotic optical properties are the subject of widespread research.  In experiments at SLAC, intense laser light (red) shining through a magnesium oxide crystal excited the outermost " valence " electrons of oxygen atoms deep inside it.  LCLS works like an extraordinary strobe light: Its ultrabright X-rays take snapshots of materials with atomic resolution and capture motions as fast as a few femtoseconds, or millionths of a billionth of a second. For comparison, one femtosecond is to a second what seven minutes is to the age of the universe.  A 'nonlinear' effect that seemingly turns materials transparent is seen for the first time in X-rays at SLAC's LCLS.  Leiden physicists have manipulated light with large artificial atoms, so-called quantum dots. Before, this has only been accomplished with actual atoms. It is an important step toward light-based quantum technology.  In a tiny quantum prison, electrons behave quite differently as compared to their counterparts in free space. They can only occupy discrete energy levels, much like the electrons in an atom-for this reason, such electron prisons are often called "artificial atoms".  When two atoms are placed in a small chamber enclosed by mirrors, they can simultaneously absorb a single photon. 
Comments: 41 Pages.
[v1] 2016-12-08 06:40:27
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