Geometry and Vibrational Spectra of Alkaline‐Earth Dihalides. II. CaF2, SrF2, and BaF2
Geometry and Vibrational Spectra of Alkaline‐Earth Dihalides. II. CaF2, SrF2, and BaF2
复制标题
碱土二卤化物 II 的几何结构和振动光谱。
DOI：
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发表时间：
1969
期刊：
影响因子：
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通讯作者：
D. White
中科院分区：
文献类型：
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作者：
V. Calder;D. E. Mann;K. Seshadri;M. Allavena;D. White
本文报道了20°K时40CaF_2、44CaF_2、86SrF_2、88SrF_2和BaF_2在固体氪基质中的红外光谱。从精确测量同位素取代的振动模式的位移的上限和下限的顶角，这些分子可以建立。基于这些极限的顶角的平均值对于CaF 2为140°，对于SrF 2为108°，并且对MgF 2的早期数据的重新分析给出了158°。对于BaF 2，顶角估计为100°。使用价力场的一组力常数已获得从测量的基本频率，以及近似值的非谐修正这些振动模式。由振动频率和分子几何构型计算的统计熵与热力学测量结果吻合得很好。
The infrared spectra of 40CaF2, 44CaF2, 86SrF2, 88SrF2, and BaF2 trapped in solid krypton matrices at 20°K are reported. From precise measurements of the shifts of the vibrational modes on isotopic substitution upper and lower limits for the apex angles of these molecules can be established. The mean values of the apex angle based on these limits are found to be 140° for CaF2, 108° for SrF2, and a reanalysis of the earlier data for MgF2 gives 158°. For BaF2 the apex angle has been estimated at 100°. Using a valence force field a set of force constants have been obtained from the measured fundamental frequencies, as well as approximate values for the anharmonic corrections to these vibrational modes. The statistical entropies calculated from the vibrational frequencies and molecular geometries are in excellent agreement with the thermodynamic measurements.