Atoms Fly Apart in Direct Crystal Melting

Apr 19, 2007
Atoms Fly Apart in Direct Crystal Melting
Photo courtesy of CONTAX images.

Using an intense laser and ultra-fast x-rays, Stanford Synchrotron Radiation Laboratory (SSRL) researchers have observed the atomic events involved in rapid crystal melting.

Ordinary thermal melting determines the fate of an ice cube in a cup of tea or an icicle out in the blazing sun. The slow-acting heat causes atomic nuclei within the ice to vibrate destructively, disrupting the chemical interactions between the atoms. This allows the ice to relax its shape from an ordered crystal to a disordered liquid.

At the Sub-Picosecond Pulse Source (SPPS), scientists used an alternative route to crystal melting that enabled them to make a "movie" of the atomic motions that lead to crystal disordering. The international collaboration used an ultra-fast, high-energy laser to rapidly heat the electrons in a crystal without heating the atomic nuclei; the laser warmed the outer electrons while leaving the heavy core of the atom cold. In this "electronically driven melting," the electrons gained energy and flew out of their regular orbit around the core, instantly breaking the chemical bonds they had shared with electrons from neighboring atoms.

Short bursts of x-rays provided by the SPPS measured the atomic positions of the atoms in a semiconductor material. The data, published recently in Physical Review Letters, revealed that when their bonds destabilized, the atoms moved apart from each other quickly, as if repelling each other. The semiconductor material had visible melting damage after being struck by the laser.

"This research provides verification that intense ultra-fast x-ray sources like the upcoming Linac Coherent Light Source (LCLS) will make possible the study of previously inaccessible material properties," said SSRL researcher Patrick Hillyard.

Source: by Heather Rock Woods, Stanford Linear Accelerator Center

Explore further: Decoding the brain: Scientists redefine and measure single-neuron signal-to-noise ratio

Related Stories

Scientists unravel elusive structure of HIV protein

13 hours ago

HIV, or human immunodeficiency virus, is the retrovirus that leads to acquired immunodeficiency syndrome or AIDS. Globally, about 35 million people are living with HIV, which constantly adapts and mutates ...

Producing spin-entangled electrons

11 hours ago

A team from the RIKEN Center for Emergent Matter Science, along with collaborators from several Japanese institutions, have successfully produced pairs of spin-entangled electrons and demonstrated, for the ...

Recommended for you

The ins and outs of quantum chromodynamics

9 hours ago

Quarks and antiquarks are the teeny, tiny building blocks with which all matter is built, binding together to form protons and neutrons in a process explained by quantum chromodynamics (QCD).

Engineers give invisibility cloaks a slimmer design

11 hours ago

Researchers have developed a new design for a cloaking device that overcomes some of the limitations of existing "invisibility cloaks." In a new study, electrical engineers at the University of California, ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.