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Microcrystal Electron Diffraction of Small Molecules
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Transición de fusión heterogénea a homogénea visualizada con difracción de electrones ultrarrápida
1SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA. mmo09@slac.stanford.edu glenzer@slac.stanford.edu.
Science (New York, N.Y.)
|June 30, 2018
Resumen
La fusión láser ultra rápida del oro muestra dos vías distintas: fusión heterogénea lenta y fusión homogénea rápida. Esto revela ideas críticas sobre la dinámica de la materia bajo condiciones extremas.
Área de la Ciencia:
- Ciencias de los materiales
- Física de la materia condensada
- Química Física
Sus antecedentes:
- La excitación láser ultrarrápida lleva a la materia a estados de no equilibrio.
- Comprender las transiciones de fase sólido-líquido en condiciones extremas es crucial.
Objetivo del estudio:
- Para visualizar y entender la dinámica a escala atómica de la fusión ultra rápida del oro.
- Diferenciar entre regímenes de fusión heterogéneos y homogéneos.
Principales métodos:
- Difracción de electrones de energía de megaelectrones voltios utilizados.
- Muestras de oro analizadas sometidas a excitación láser ultrarrápida.
Principales resultados:
- Se observa una fusión heterogénea (1001000 ps) a densidades de energía más bajas.
- Se observó una fusión homogénea catastrófica (1020 ps) a densidades de energía más altas.
- Se proporcionan pruebas de coexistencia sólido-líquido y se determinan las temperaturas de iones/electrones, revelando el sobrecalentamiento.
Conclusiones:
- Se limitó la velocidad de acoplamiento electrón-ion y se determinó la temperatura de Debye.
- Se ha demostrado sensibilidad a la fusión de las semillas de nucleación.
- Estableció un marco para comprender las transiciones de fase de no equilibrio en los metales.
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