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41.0GPa。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3.5GPa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发生了液固相变。当压力增加到19.0GPa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 demon- strate that liquid 2NH3 · H2O transforms to a solid phase at 3.5 GPa, evidenced by an ab- rupt 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 Ra- man scattering results of 2NH3· H2O provide significant information for understanding the physics of the large icy bodies in the solar system.
出处
《光散射学报》
北大核心
2012年第2期168-171,共4页
The Journal of Light Scattering
基金
国家自然科学基金(10574054
11004074)
国家重点基础研究发展计划项目(2011CB808200)
