Ns-scale time resolved laser excited resonance emission spectra of sulfur dioxide (SO2) gas were acquired in two different deep UV wavelength regions. Both wavelength regions are in electronic resonance of SO2 molecule but the temporal responses of the two emission spectra were different in ns time scale. When excited at 220.56 nm, the emission spectra were observed at almost the same time as the excitation laser and we conclude that the spectra were resonance Raman scattering. On the other hand, when excited at 279.60 nm, the emission spectra were observed approximately 5 ns after the excitation laser and we conclude that the spectra were resonance fluorescence. 5 ns difference in time is equivalent to 75 cm in distance measurement of ToF LIDAR, which is not negligible in short range or precision-needed situations.
Ichikawa et al. (2026) studied this question.