Theory and experiment on the terahertz vibrational spectrum of ferulic acid

Abstract

Ferulic acid (FA, C10H10O4), a type of hydroxycinnamic acid derivative, has beneficial pharmacological effects and biological activities and is known for its high application value in medicine, health care, and cosmetic products. The vibration spectrum of FA ranging from 0.3 THz to 2.0 THz has been investigated by terahertz time-domain spectroscopy. The characteristic absorption peaks located at 0.937, 1.159, 1.464, 1.694, and 1.910 THz are obtained experimentally. To understand the origin of the characteristic absorption peaks of FA, density functional theory calculations based on isolated molecule and crystalline structure are separately performed to differentiate the intramolecular and intermolecular vibrational modes. Combined analysis of the experimental and theoretical results informs that the characteristic absorption peak at 1.464 THz comes from intramolecular interaction, and the ones at 0.937, 1.159, 1.694, and 1.910 THz originate from intermolecular collective vibrational modes.