Ammonia is predicted to be one of the major components in the depths of the ice giant planets Uranus and Neptune. Their dynamics, evolution, and interior structure are insufficiently understood and models rely imperatively on data for equation of state and transport properties. Despite its great significance, the experimentally accessed region of the ammonia phase diagram today is still very limited in pressure and temperature. Here we push the probed regime to unprecedented conditions, up to $\sim 350\mathrm{GPa}$ and $\sim 40000\mathrm{K}$. Along the Hugoniot, the temperature measured as a function of pressure shows a subtle change in slope at $\sim 7000\mathrm{K}$ and $\sim 90\mathrm{GPa}$, in agreement with ab initio simulations we have performed. This feature coincides with the gradual transition from a molecular liquid to a plasma state. Additionally, we performed reflectivity measurements, providing the first experimental evidence of electronic conduction in high-pressure ammonia. Shock reflectance continuously rises with pressure above 50 GPa and reaches saturation values above 120 GPa. Corresponding electrical conductivity values are up to 1 order of magnitude higher than in water in the 100 GPa regime, with possible significant contributions of the predicted ammonia-rich layers to the generation of magnetic dynamos in ice giant interiors.

中文翻译：

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冲击压缩液氨的金属化

预计氨是冰巨行星天王星和海王星深处的主要成分之一。人们对它们的动力学，演化和内部结构了解不足，并且模型必须依赖于状态和传输特性方程的数据。尽管具有很大的意义，但是今天氨相图的实验访问区域在压力和温度上仍然非常有限。在这里，我们将探索的政权推向前所未有的条件，直至$〜350\mathrm{GPa}$ 和 $〜40000\mathrm{ķ}$。沿着Hugoniot，测得的温度是压力的函数，显示出坡度的细微变化$〜7000\mathrm{ķ}$ 和 $〜90\mathrm{GPa}$，与我们从头开始进行的仿真一致。该特征与从分子液体到等离子体状态的逐渐过渡一致。此外，我们进行了反射率测量，为高压氨中的电子传导提供了第一个实验证据。压力高于50 GPa时，冲击反射率会持续上升，而饱和压力则高于120 GPa。相应的电导率值在100 GPa的情况下比水中的电导率值高1个数量级，其中预测的富含氨的层可能会对冰巨内部的磁动力产生产生重大影响。