Terahertz spectroscopy of vibrational modes of molecular crystal of sucrose

A molecular single crystal of sucrose is studied by a terahertz time-domain spectroscopy. The crystal's vibrational modes in the frequency range of 0.1-4 THz are identified. In addition, a mapping of dipoles of these vibrational modes to the crystal orientation is performed. The measured spectra for the various crystal orientations identify clearly an orientation of dipole associated with these modes. The quadrupole moments are observed.