Terahertz (THz) spectra of bentazon are determined within the range of 0.3-2.4 THz at room temperature. Density functional methods are used to compute the THz spectra using three different programs: Gaussian03 for isolated-molecule form, DMol3 and CRYSTAL09 for solid-state forms. Among the three, the computed THz spectrum of CRYSTAL09 shows better bond length and angle agreements with X-ray experimental results, and corresponds with observed THz experiment spectral characteristics. The isolated-molecule vibrational mode values are less by half than those derived from solid-state calculations. The last five peak positions of the two solid-state computations coincide with each other. Moreover, all the experimental THz absorption peaks are assigned by utilizing CRYSTAL09.
© 2011 Chinese Optics Letters
Spectroscopy, imaging, and sensing using terahertz radiation
Huali Wang and Qiang Wang, "Modeling the THz spectrum of the bentazon," Chin. Opt. Lett. 9, 110011- (2011)