Melting of compressed iron-alloys by monitoring atomic dynamics

地核占地球体积的16%。它主要由铁组成，但也包括一些较轻的元素，这些元素的存在（而不是性质）是通过地球物理测量推断出来的。岩心由一个固体的内部部分组成，周围是一个对流的液体外层。它创造了地球的磁场，保护地球免受太阳耀斑等太空天气事件的影响，并在液态地核冻结时为板块构造提供热量。地核开始于地球表面以下约2900公里处，因此很难确定其确切的组成和温度分布，因此科学家依靠实验室实验和不断发展的模型来推断地核的特征。根据NSF的奖励，PI正在开发Mössbauer效应的新应用，利用同步加速器x射线辐射填充铁镍合金熔化曲线上的数据点，铁镍合金是地核的主要组成部分。该项目将为本科生和研究生提供支持和培训，他们将接受利用国家同步辐射设施进行实验研究的培训。激光加热的金刚石砧细胞，时间分辨同步加速器Mössbauer光谱，x射线衍射和最近开发的快速温度读出光谱仪用于进行这些测量。以铁的Mössbauer共振能量之一的x射线光子聚焦在激光加热的金刚石砧细胞中的样品上，当熔化发生时，特征信号Mössbauer突然下降。因此，时间分辨Mössbauer光谱为样品室中形成的第一个熔体提供了极好的诊断。这些结果将代表着理解富铁合金在类地行星核心条件下熔化的重要一步。除此之外，还应用了一种测量原子动力学的新方法来确定高压下的熔化。拟议的研究议程为参与的学生提供了一个独特的协同和训练基地，使他们能够在多个设施中应用最先进的实验技术，包括国家设施中的先进辐射源，以解决地球材料高压熔化调查领域的科学问题，这是一个活跃的研究领域。

The Earth's core is 16% of the planet by volume. It is composed primarily of iron, but includes a quantity of lighter elements whose presence, but not identity, is inferred from geophysical measurements. The core consists of a solid inner section surrounded by a convecting, liquid outer layer. It creates Earth's magnetic field, protecting the planet from space weather events such as solar flares, and provides the heat for plate tectonics as the liquid core freezes. The core begins approximately 2900 km below the Earth's surface, making it difficult to determine its exact composition and temperature profile, so scientists rely on laboratory experiments and an evolving model to infer core characteristics. Under this NSF award, the PI is developing a new application of the Mössbauer effect utilizing synchrotron X-radiation to populate data points on the melting curve of an iron-nickel alloy, a primary component of Earth's core. This project will provide support and training for students at the undergraduate and graduate level, who will be trained in experimental research utilizing national synchtrotron radiation facilities.Laser heated diamond anvil cells, time-resolved synchrotron Mössbauer spectroscopy, x-ray diffraction and a recently developed fast temperature readout spectrometer are used to carry out these measurements. X-ray photons at one of iron's Mössbauer resonant energies are focused on the sample in a laser heated diamond anvil cell, and when melting occurs, the characteristic Mössbauer signal abruptly decreases. Thus, time-resolved Mössbauer spectroscopy provides an excellent diagnostic for the first melt formed in the sample chamber. These outcomes will represent a significant step towards understanding the melting of iron-rich alloys at conditions of terrestrial-type planetary cores. This is in addition to applying a new method that measures the atomic dynamics to the effort of determining melting at high-pressures. The proposed research agenda offers a unique synergy and training ground for the involved students to apply state-of-the-art experimental techniques at multiple facilities, including advanced radiation sources at national facilities, to scientific problems in the area of high-pressure melting investigations of Earth materials, an active area of research.