摘要
为深入了解β-D-吡喃半乳糖在太赫兹波段的光谱特性,利用太赫兹时域光谱技术测量了室温下β-D-吡喃半乳糖晶体在0.3～3.0THz范围内的吸收谱及折射率谱,同时利用傅里叶变换红外光谱技术获得了半乳糖在1.5～19.5THz之间的吸收谱。实验研究的同时,运用密度泛函理论和6-311+G**基组计算了气态孤立β-D-吡喃半乳糖分子的结构及其在太赫兹波段的振动频率,并据此对实验光谱吸收峰进行了指认。研究结果表明,除了因为分子间效应而导致的少许偏移外,理论计算结果与实验数据吻合得很好;实验光谱在6THz以上频段的共振吸收峰来源于明确的分子内振动模式,而6THz以下低频段的共振吸收峰则主要来源于分子间氢键或晶体的声子模式。实验和理论研究的对比表明物质的远红外吸收特征对于分子的结构和空间排列非常敏感。
In order to deeply understand the spectral characteristics of β-D-galactopyranose in the terahertz region, terahertz time-domain spectroscopy was used to measure the absorption coefficient and refractive index in the frequency range 0. 3-3. 0 THz at room temperature, and Fourier transform infrared spectroscopy was also used to obtain the absorption spectrum between 1.5 and 19. 5 THz. In parallel with the experimental study, the 6-311＋G＊＊ basis set and density functional theory（DFT） were applied to obtain the structure and vibrational frequencies of the isolated β-D-galactopyranose molecule at in phase. The observed vibrational spectra were assigned according to the DFT calculations. Results show that the theoretical calculations are in good agreement with the experimental data except somewhat blue shifts due to the intermolecular interactions. The observed resonances at the high frequency above 6 THz originate from distinct intra-molecular vibrational modes, while at the low frequency below 6 THz the observed resonances are dominated by vibrations of hydrogen bonds between the molecules or phonon modes. The comparison of experimental and theoretical studies shows that far-infrared absorption features are highly sensitive to the structure and spatial arrangement of molecules.
出处
《光谱学与光谱分析》
SCIE
EI
CAS
CSCD
北大核心
2008年第4期721-725,共5页
Spectroscopy and Spectral Analysis
基金
国家自然科学基金项目(60374051)资助
关键词
β-D-吡喃半乳糖
太赫兹时域光谱
傅里叶变换红外光谱
密度泛函理论
β-D-galactopyranose
Terahertz time-domain spectroscopy
Fourier transform infrared spectroscopy
Density functional theory
