Tamura Kohei, Tsuboi Motohiro, Furukawa Kuniyuki, Akao Ken-Ichi, Sato Harumi, Ozaki Yukihiro
Applicative Solution Lab Division, JASCO Corporation, 2967-5 Ishikawa-machi, Hachioji, Tokyo 192-8537, Japan.
Department of Applied Chemistry for Environment, School of Biological and Environmental Sciences, Kwansei Gakuin University, 1 Gakuen-Uegahara, Sanda, Hyogo 669-1330, Japan.
Appl Spectrosc. 2025 Sep;79(9):1356-1366. doi: 10.1177/00037028251333469. Epub 2025 May 5.
In this study, Raman spectra (3700-10 cm) and attenuated total reflection infrared-far-infrared (ATR-IR/FIR) spectra (4000-50 cm) including low-frequency region were measured for amorphous rocks, which were five types of obsidians whose formation ages and sources are different and pitchstone to clarify the differences in water content (free and bound water species), their Si-O bonds and possible linkage with a metal ion, and the mean atomic volume. In order to explore these points, we focused on infrared (IR) absorptions of hydroxyl (OH) groups that is observed in the 4000-3000 cm region, those of Si-O bond that is identified in the 1300-850 cm region and a Boson peak that appears in a low-frequency region of Raman spectra, respectively. IR absorption of Si-O stretching was detected for all samples and that of OH stretching and H-O-H bending was also detected in some rocks. Therefore, using IR spectroscopy was useful to discriminate each rock based on the water content and the environment of Si-O bonds. On the other hands, a Boson peak could be detected for the low-frequency region below 60 cm of Raman spectra, which appears in amorphous solids. This study is the first finding that the Raman shift of Boson peak was different among similar natural glassy rocks from multiple sources and it means that the mean atomic volume of samples was different. In addition, sharp bands of Raman scattering which came from inorganic substances such as feldspar helped to identify ingredients in samples. As a results, we made clear that using both IR and Raman including low-frequency regions is effective to identify the same types of natural amorphous rocks.
在本研究中，我们对非晶质岩石进行了拉曼光谱（3700 - 10 cm）和衰减全反射红外 - 远红外（ATR - IR/FIR）光谱（4000 - 50 cm）测量，其中包括低频区域。这些非晶质岩石有五种形成年龄和来源不同的黑曜石以及松脂岩，目的是阐明其含水量（自由水和结合水种类）、Si - O键以及与金属离子的可能联系和平均原子体积的差异。为了探究这些要点，我们分别关注了在4000 - 3000 cm区域观察到的羟基（OH）基团的红外（IR）吸收、在1300 - 850 cm区域识别出的Si - O键的红外吸收以及拉曼光谱低频区域出现的玻色子峰。所有样品都检测到了Si - O伸缩振动的红外吸收，并且在一些岩石中还检测到了OH伸缩振动和H - O - H弯曲振动的红外吸收。因此，利用红外光谱基于含水量和Si - O键的环境来区分每种岩石是有用的。另一方面，在拉曼光谱低于60 cm的低频区域可以检测到玻色子峰，这出现在非晶质固体中。本研究首次发现，来自多个来源的类似天然玻璃质岩石中玻色子峰的拉曼位移不同，这意味着样品的平均原子体积不同。此外，来自长石等无机物的拉曼散射尖锐谱带有助于识别样品中的成分。结果，我们明确了使用包括低频区域的红外和拉曼光谱来识别同类型天然非晶质岩石是有效的。
