Centre for Science at Extreme Conditions and School of Physic and Astronomy, University of Edinburgh, Edinburgh, EH9 3JZ, United Kingdom.
Phys Rev Lett. 2012 Mar 23;108(12):125501. doi: 10.1103/PhysRevLett.108.125501. Epub 2012 Mar 19.
We used Raman and visible transmission spectroscopy to investigate dense hydrogen (deuterium) up to 315 (275) GPa at 300 K. At around 200 GPa, we observe the phase transformation, which we attribute to phase III, previously observed only at low temperatures. This is succeeded at 220 GPa by a reversible transformation to a new phase, IV, characterized by the simultaneous appearance of the second vibrational fundamental and new low-frequency phonon excitations and a dramatic softening and broadening of the first vibrational fundamental mode. The optical transmission spectra of phase IV show an overall increase of absorption and a closing band gap which reaches 1.8 eV at 315 GPa. Analysis of the Raman spectra suggests that phase IV is a mixture of graphenelike layers, consisting of elongated H2 dimers experiencing large pairing fluctuations, and unbound H2 molecules.
我们使用拉曼和可见传输光谱法在 300 K 下研究了高达 315（275）GPa 的高密度氢（氘）。在大约 200 GPa 时，我们观察到了相变，我们将其归因于先前仅在低温下观察到的相 III。在 220 GPa 时，它被可逆地转变为新相 IV，其特征是第二振动基频和新的低频声子激发的同时出现，以及第一振动基频模式的急剧软化和展宽。相 IV 的光学透射光谱显示出整体吸收增加和带隙闭合，在 315 GPa 时达到 1.8 eV。拉曼光谱分析表明，相 IV 是类石墨烯层的混合物，由经历大配对涨落的拉长的 H2 二聚体和未结合的 H2 分子组成。
