Vibrational Mode Assignment in the Terahertz Frequency Region by Isotope Shift: Anthracene in Solid State

Abstract

Abstract The low-frequency spectra of normal anthracene and anthracene-d10 in the solid state were measured by a high-resolution terahertz spectrometer. We observed the isotope shift of the vibrational frequency in the THz frequency region at 5 K. The vibrational mode assignment was performed based on the DFT calculation for the isolated species and observed isotope shifts. We also conducted solid-state DFT calculations using CRYSTAL09 to confirm the mode assignment. The correlation field splitting for the intramolecular mode due to the dipole–dipole interaction is quantitatively discussed.