氨的半水合物的高压拉曼光谱研究

摘要

在室温条件下,利用金刚石对顶砧超高压技术,对氨的半水合物(2NH3 · H2O)进行了原位高压拉曼光谱研究,采用红宝石荧光压标测压,实验的最高压力为41.0 GPa.装入金刚石对顶砧样品腔的初始样品为液态的氨的半水合物,当压力达到3.5 GPa时,显微镜下观察到整个样品腔内均匀的出现块状晶体,同时,测量到的拉曼谱上出现许多新的拉曼峰.因此,我们判断在此压力下液态的2NH3·H2O发生了液同相变.当压力增加到19.0 GPa左右时,2NH3·H2O的拉曼频移随压力变化的曲线有拐点,并且具有软化特性的N-H伸缩振动模式消失.我们分析这是因为在高压下,通过O-H…N成键的Ⅱ型氨分子发生了旋转,所以2NH3·H2O在此压力下发生了一次固固相变.%High pressure Raman scattering studies have been performed on liquid ammonia hemihydrates (2NH3 · H2O) at room temperature up to 41.0 GPa. The results demonstrate that liquid 2NH3 · H2O transforms to a solid phase at 3. 5 GPa, evidenced by an abrupt discontinuity of the intramolecular vibration frequencies. Upon increasing pressure, a solid-solid phase transition is observed at about 19. 0 GPa. This phase transition originates from the rotation of type II ammonia molecule via the O-H···N bond. High pressure Raman scattering results of 2NH3 · H2O provide significant information for understanding the physics of the large icy bodies in the solar system.