Fig. 1From: Identification of different parts of Panax notoginseng based on terahertz spectroscopyTHz spectra of four different parts, a is time-domain spectroscopy; b is absorption coefficient spectrum in 0.5–2 THz; c is refractive Index in 0.2–1.5 THz; and d is frequency domain in 0.5–2 THzBack to article page