Heterogeneous to homogeneous melting transition visualized with ultrafast electron diffraction
Heterogeneous to homogeneous melting transition visualized with ultrafast electron diffraction
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DOI：
10.1126/science.aar2058
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发表时间：
2018-06-29
期刊：
影响因子：
56.9
通讯作者：
Glenzer, S. H.
中科院分区：
文献类型：
--
作者：
Mo, M. Z.;Chen, Z.;Glenzer, S. H.
超快激光对物质的激发导致了具有复杂固-液相变动力学的非平衡态。我们使用兆电子伏能量的电子衍射来可视化原子尺度长度上的金的超快熔化。对于接近不可逆熔化制度的能量密度，我们首先观察到在100至1000皮秒的时间尺度上的非均匀熔化，在更高的能量密度下，在10至20皮秒内灾难性地过渡到均匀熔化。我们发现了固液共存的证据。我们确定了离子和电子的温度演变，并发现过热的条件。我们的结果限制了电子-离子耦合速率，确定德拜温度，并揭示了熔化的成核种子的敏感性。
The ultrafast laser excitation of matters leads to nonequilibrium states with complex solid-liquid phase-transition dynamics. We used electron diffraction at mega-electron volt energies to visualize the ultrafast melting of gold on the atomic scale length. For energy densities approaching the irreversible melting regime, we first observed heterogeneous melting on time scales of 100 to 1000 picoseconds, transitioning to homogeneous melting that occurs catastrophically within 10 to 20 picoseconds at higher energy densities. We showed evidence for the heterogeneous coexistence of solid and liquid. We determined the ion and electron temperature evolution and found superheated conditions. Our results constrain the electron-ion coupling rate, determine the Debye temperature, and reveal the melting sensitivity to nucleation seeds.