Optical studies of materials at high pressure-temperature (P-T) conditions provide insights into their physical properties that may be inaccessible to direct determination at extreme conditions. Incandescent light sources, however, are insufficiently bright to optically probe samples with radiative temperatures above ∼1000 K. Here we report on a system to perform optical absorption experiments in a laser-heated diamond anvil cell at T up to at least 4000 K. This setup is based on a pulsed supercontinuum (broadband) light probe and a gated CCD detector. Precise and tight synchronization of the detector gates (3 ns) to the bright probe pulses (1 ns) diminishes the recorded thermal background and preserves an excellent probe signal at high temperature. We demonstrate the efficiency of this spectroscopic setup by measuring the optical absorbance of solid and molten (Mg,Fe)SiO3, an important constituent of planetary mantles, at P ∼30 GPa and T ∼1200 K to 4150 K. Optical absorbance of the hot solid (Mg,Fe)SiO3 is moderately sensitive to temperature but increases abruptly upon melting and acquires a strong temperature dependence. Our results enable quantitative estimates of the opacity of planetary mantles with implications to their thermal and electrical conductivities, all of which have never been constrained at representative P-T conditions, and call for an optical detection of melting in silicate-bearing systems to resolve the extant ambiguity in their high-pressure melting curves.

中文翻译：

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超连续谱脉冲的门控检测能够在极端压力-温度条件下对固体和熔融硅酸盐进行光学探测

在高压-温度 (PT) 条件下对材料进行光学研究，可以深入了解它们在极端条件下可能无法直接确定的物理特性。然而，白炽光源的亮度不足以对辐射温度高于 1000 K 的样品进行光学探测。在这里，我们报告了一种在 T 高达至少 4000 K 的激光加热金刚石砧座中进行光吸收实验的系统。这设置基于脉冲超连续谱（宽带）光探头和门控 CCD 检测器。检测器门 (3 ns) 与明亮探针脉冲 (1 ns) 的精确和紧密同步减少了记录的热背景，并在高温下保留了出色的探针信号。我们通过测量固体和熔融 (Mg,Fe)SiO3（行星地幔的重要成分）在 P~30 GPa 和 T~1200 K 至 4150 K 的光吸收率来证明这种光谱装置的效率。固体 (Mg,Fe)SiO3 对温度的敏感性适中，但在熔化时突然增加，并具有很强的温度依赖性。我们的结果能够定量估计行星地幔的不透明度及其热导率和电导率，所有这些都从未在代表性 PT 条件下受到限制，并呼吁对含硅酸盐系统中的熔化进行光学检测，以解决现存的模糊性在它们的高压熔化曲线中。热固体 (Mg,Fe)SiO3 的光吸收对温度适度敏感，但在熔化时突然增加，并具有很强的温度依赖性。我们的结果能够定量估计行星地幔的不透明度及其热导率和电导率，所有这些都从未在代表性 PT 条件下受到限制，并呼吁对含硅酸盐系统中的熔化进行光学检测，以解决现存的模糊性在它们的高压熔化曲线中。热固体 (Mg,Fe)SiO3 的光吸收对温度适度敏感，但在熔化时突然增加，并具有很强的温度依赖性。我们的结果能够定量估计行星地幔的不透明度及其热导率和电导率，所有这些都从未在代表性 PT 条件下受到限制，并呼吁对含硅酸盐系统中的熔化进行光学检测，以解决现存的模糊性在它们的高压熔化曲线中。