Structural Studies on Metallization of Solid Oxygen

1.利用ESRF和PF中的高能高亮度同步辐射源，在室温下对固体氧进行了高达181 GPa的能量色散粉末x射线衍射研究。在96 GPa时观察到一个新的高压结构转变。向zeta-O_2的相变归因于S.Desgreniers等人先前报道的金属化。金属相在181 gpa下稳定。为了研究固体氧在96 GPa时结构向金属相转变的过程，在室温下对固体氧进行了高达110 GPa的高压拉曼光谱分析。虽然epsilon-O_2相的振子波数与压力呈线性关系，其系数为2.33 cm^<-1>/GPa，在94 GPa时达到1753 cm^<-1>，但随着结构向金属相的转变，epsilon-O_2相的振子和振子波数逐渐消失。在25 GPa和650 K条件下，采用应变退火法制备了epsilon-O_2相单晶，该单晶具有明显的二色性，并在高达60 GPa的压力下进行了红外吸收实验。在1500 cm^<-1>附近的红外活性振子基波至少分成三个波段。红外振动频率的压力依赖性在25 GPa附近最小，30 GPa以上的正压力系数在1.2 ~ 1.7 cm^<-1>/GPa之间。这些结果表明金属zeta-O_2相是由O_2分子组成的。

1.By using high-energy and high-brilliance synchrotron radiation source in ESRF and PF,an energy-dispersive powder X-ray diffraction study on solid oxygen has been carried out up to 181 GPa at room temperature. A new high-pressure structural transition was observed at 96 GPa. The phase transition to zeta-O_2 is ascribed to metallization previously reported by S.Desgreniers et al. The metallic phase was stable up to 181 GPa.2.High-pressure Raman spectroscopy of solid oxygen has been carried out up to 110 GPa at room temperature in order to study the structural transition to the metallic phase at 96 GPa. The vibron and librons in the epsilon-O_2 phase became undetectable corresponding to the structural transition to metallic phase, although the vibron wavenumber in the epsilon-O_2 phase has shown a linear pressure dependence with a coefficient of 2.33 cm^<-1>/GPa and reached 1753 cm^<-1> at 94 GPa.3.Single-crystal of the epsilon-O_2 phase, which exhibited a remarkable dichromatic character, were prepared by a strain anneal method under a condition of 25 GPa and 650 K and were used for infrared absorption experiments under pressure up to 60 GPa. The IR-active vibron fundamental around 1500 cm^<-1> split into at least three bands. The pressure dependence of frequency of the IR-vibrons had a minimun around 25 GPa and above 30 GPa showed positive pressure coefficients between 1.2-1.7 cm^<-1>/GPa.Thes results suggested that the metallic zeta-O_2 phase consisted of O_2 molecules.