Lepodise Lucia M
Botswana International University of Science and Technology, Palapye, Botswana.
Heliyon. 2020 Nov 27;6(11):e05577. doi: 10.1016/j.heliyon.2020.e05577. eCollection 2020 Nov.
Fourier Transform Infrared Spectroscopy was employed to measure the low frequency terahertz transmission spectrum of benzoic acid over a wide temperature range. One broad absorption peak was observed at room temperature but more peaks appeared as the sample was cooled. All the peaks shifted to higher frequencies with the decrease in temperature and they displayed a rate of change in the range of (2-5.6) x 10cmK. An anomalous behavior was observed in the peak width and the peak intensity for some absorption peaks and this was attributed to the peaks being composite. There is a good agreement between the model of benzoic acid crystal and the experiment. The QUANTUM ESPRESSO code utilizing the PBEsol functional proved to be slightly better than the GAUSSIAN 03 method which employed NC-PBE functional in predicting the absorption peaks. A comparison was made of these results and the previous studies done using the THz-TDS. These results proved the ability of the FTIR technique in performing low frequency THz measurements.
采用傅里叶变换红外光谱法在较宽温度范围内测量苯甲酸的低频太赫兹透射光谱。室温下观察到一个宽吸收峰，但随着样品冷却出现了更多峰。所有峰随温度降低向更高频率移动，其变化速率在(2 - 5.6)×10⁻²cm⁻¹K范围内。观察到一些吸收峰的峰宽和峰强度存在异常行为，这归因于这些峰是复合峰。苯甲酸晶体模型与实验结果吻合良好。利用PBEsol泛函的QUANTUM ESPRESSO代码在预测吸收峰方面比采用NC - PBE泛函的GAUSSIAN 03方法略胜一筹。对这些结果与之前使用太赫兹时域光谱法（THz - TDS）所做的研究进行了比较。这些结果证明了傅里叶变换红外光谱（FTIR）技术进行低频太赫兹测量的能力。
