Isotopic analysis based on terahertz spectrum

As a new promising detection technology in the terahertz research field, the terahertz time-domain spectroscopy (THz-TDS) has very broad application potential in many fields because its advantage on the characteristic spectrum, wide spectrum and non-destructive analysis of interested substances. In this paper, the terahertz absorption spectra of gases mixed with ¹²CO and ¹³CO in the spectrum range of 0.5–2.5 THz are measured by terahertz time-domain spectroscopy for the first time. Several isotopologues can be clearly distinguished based on the difference in their rotational energies and the consequent terahertz spectrum. The experimental results show that ¹²CO and ¹³CO have obvious characteristic absorption peaks in the spectrum range of 0.5–2.5 THz due to the difference in rotational energy, and the rotational constant B can be calculated according to the experimental values to distinguish the two gaseous isotopologues. The frequency positions of the characteristic absorption peak measured by this experiment and the rotation constant B calculated according to the experimental values are compared with those previous theoretical calculations and experimental results, and they are in good agreement. This result lays a foundation for developing more sophisticated terahertz instruments to the detection of different isotopologues.