Study of the Pigment Spectroscopy in the Terahertz Band

Pigments are essential materials that make cultural relics vivid and visually striking, with their varied colors reflecting the characteristics of different historical periods. Various nondestructive testing (NDT) methods have been used to analyze pigment composition in cultural relics. Among these methods, terahertz waves, which have been introduced over the past three decades, have emerged as a valuable tool for NDT. The application of terahertz technology in pigment research is of enormous importance. Traditional terahertz time-domain spectroscopy systems operate within a spectral range of 0. 25 - 3 THz. In this study, a broad-spectrum terahertz time-domain spectroscopy system was developed to investigate six commonly used pigments for cultural relic protection. The transmission spectra of these pigments were measured over an extended range of 0. 25-7 THz, and their refractive index and absorption coefficients were calculated. The experimental results were compared with those obtained using Fourier transform infrared spectroscopy, thereby confirming the reliability of the terahertz experimental results.