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Nitrogen atoms like to travel in pairs
In the current online edition of Physical Review Letters, researchers from the Carnegie Institution's Geophysical Laboratory report changes in the melting temperature of solid nitrogen at pressures up to 120 gigapascals (more than a million atmospheres) and temperatures reaching 2,500° Kelvin (more than 4000° Fahrenheit).
The colorful patterns formed by the response of superconducting 'artificial atoms' to a new probe called amplitude spectroscopy serve as an identifying fingerprint for a given atom.
These results, plus observed changes in the structure of solid nitrogen at high pressures, could lead to new high energy nitrogen- or hydrogen-based fuels in the future. Hypothesized nitrogen polymers could form materials with higher energy content than any known non-nuclear material.
Alexander Goncharov, Viktor Struzhkin, and Russell Hemley from Carnegie, with Jonathan Crowhurst from Lawrence Livermore National Laboratory, compressed liquid nitrogen in a device known as a diamond anvil cell, which generates ultrahigh pressures by squeezing a sample between two gem-quality diamonds. Because the diamonds are transparent to most wavelengths of light, the sample can be heated by a laser during the experiment. A technique called Raman spectroscopy uses light emitted by the heated sample to analyze changes in the sample's molecular structure as they occur.
"Until now, no one had made these kinds of in situ observations of nitrogen at such extreme temperatures and pressures," says Goncharov. "Our measurements of the melting line and the vibration properties of the fluid indicated by the Raman spectroscopy give us a very clear picture of how nitrogen and its molecular bonds respond under these conditions."
Title original: Putting The Squeeze On Nitrogen For High Energy MaterialsAlexander Goncharov, Viktor Struzhkin, and Russell Hemley from Carnegie, with Jonathan Crowhurst from Lawrence Livermore National Laboratory, compressed liquid nitrogen in a device known as a diamond anvil cell, which generates ultrahigh pressures by squeezing a sample between two gem-quality diamonds. Because the diamonds are transparent to most wavelengths of light, the sample can be heated by a laser during the experiment. A technique called Raman spectroscopy uses light emitted by the heated sample to analyze changes in the sample's molecular structure as they occur.
"Until now, no one had made these kinds of in situ observations of nitrogen at such extreme temperatures and pressures," says Goncharov. "Our measurements of the melting line and the vibration properties of the fluid indicated by the Raman spectroscopy give us a very clear picture of how nitrogen and its molecular bonds respond under these conditions."
Full article: http://www.sciencedaily.com/releases/2008/09/080903134318.htm
Source: sciencedaily.com
Credit image: Carnegie Institution