Terahertz spectroscopic investigation of four kinds of vitamins

The terahertz spectra of four kinds of vitamins are presented. The refractive index and absorption spectra of these vitamins are obtained by the terahertz time-domain spectroscopy. The full-geometry optimizations and frequency calculations using the density functional theory are applied to obtain the structure and vibration frequencies of these vitamin molecules. The calculated vibration frequencies are compared with the experimental data. The results show that there are terahertz fingerprint absorptions for all of four kinds of vitamins. The terahertz absorbance spectra of vitamins result from not only the intramolecular vibration modes, but also the intermolecular interaction or phonon modes. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3259376]