Thursday, April 19, 2007

The crystal melting movie?

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

Sub-Picosecond Pulse Source (SPPS) provides short bursts of x-rays (2 x 10^6 photons in an 80 fs FWHM pulse at 8.9 keV with a 1.5% bandwidth into a 200 um by 400 um spot). The laser pulse (50fs FWHM, 20 mJ @ 800 nm) at the sample, which convolved with the x-ray pulse yields a Gaussian cross correlation of 100 fs FWHM.

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.

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