Temperature dependence of terahertz spectra of chlorophyll a and b

In this paper, we employ terahertz Time Domain Spectroscopy (THz-TDS) combined with temperature-tuned system to measure the temperature dependence of terahertz spectroscopic features of chlorophyll a and b samples. We investigated the absorbance of individual chlorophyll a and b respectively. The measured spectra showed two shoulders at 2.17 and 2.95 THz for the chlorophyll a sample, and 2.83 and 3.40 THz for the chlorophyll b sample. The measured absorption spectra were compared with the results simulated by Density Function Theory (DFT) using hybrid functional B3LYP with basis set of 6-31 G (d). The simulated results show more absorption peaks than measurement results. The discrepancy between simulation and experiment results originates from that the molecular structure used in the simulation is gas phase molecular model, which is different from crystal structure.