Study on iodine molecular isotope identification based on absorption spectrum and laser-induced fluorescence spectroscopy

Iodine isotopes can be used as tracers to study geological, marine and environmental processes and to monitor nuclear environmental safety. In view of the urgent need for the detection of iodine molecular isotopes in the field of environmental monitoring, it is urgent to carry out on-line monitoring of high sensitivity and high spectral resolution iodine isotopes. In this paper, aiming at the problem of the theoretical simulation of iodine molecular isotope spectrum, inversion of isotopic hyperfine spectral parameters, generation and identification of hyperfine spectral signals, some key techniques, such as Frank-Condon factor calculation, iodine molecular spectrum fitting, iodine molecular isotope measurement based on absorption spectrum and excitation fluorescence spectrum, are solved. The absorption spectra of iodine isotope molecules are theoretically simulated, which provides a theoretical reference for isotope discrimination based on spectra. A detection system based on absorption spectrum and Laser-induced iodine isotope fluorescence spectrum was established. The 127I2 absorption spectrum was measured by using 635 nm grating feedback ECDL (External-Cavity Diode Laser, ECDL), and the detection sensitivity was 1.2×10¹³ m^-3. The ¹²⁷I₂ excitation fluorescence detection was realized by using 532 nm YAG laser with fiber seed injection locking, and the detection sensitivity was 5.8×10¹³ m^-3. The results provide theoretical basis and technical support for the on-line rapid detection of iodine molecular isotopes based on spectra. Keywords: Iodine Molecular Isotopes; Absorption Spectrum; Laser Induced Fluorescence Spectroscopy; Frank-Condon