Monday, October 30, 2006

Just Right Ice

Another example of the Goldilocks Enigma....the X-rays were 'just right'....

Splitting Water Creates Alloy

"At first, we saw these unexpected H2 and O2 peaks in our X-ray Raman spectra," Wendy Mao tells C&EN. "Then we released pressure from the diamond anvil cell, and we actually saw gas bubbling out."

Upon further investigation, they determined that at high pressure the X-rays dissociate H2O and the resulting atoms recombine into a previously unknown solid of H2 and O2. This new "alloy" is spectroscopically distinct from a simple H2-O2 mix.

X-rays are known to create free radicals and instigate reactions at ambient pressure, but examples of similar transformations at high pressure are rare. "We managed to hit on just the right level of X-ray energy input," Hemley explains. "Any higher, and the radiation tends to pass right through the sample. Any lower, and the radiation is largely absorbed by the diamonds in our pressure apparatus."

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