## Abstract

The laser-induced fluorescence spectrum of sulfur dioxide (${\mathrm{SO}}_{2}$) in the range of 200–460 nm has been obtained with the dyer laser (579 nm) pulsed by an Nd:YAG laser as the excitation source. The transition process, both ${\mathrm{X}}^{1}{\mathrm{A}}_{1}\to {\mathrm{C}}^{1}{\mathrm{B}}_{2}$, excited by three photons and ${\mathrm{X}}^{1}{\mathrm{A}}_{1}\to {\mathrm{A}}^{1}{\mathrm{A}}_{2}$, excited by two photons, has been evaluated. The relaxation kinetics of the excited molecules in the states of ${\mathrm{C}}^{1}{\mathrm{B}}_{2}$ and ${\mathrm{A}}^{1}{\mathrm{A}}_{2}$ have been analyzed on the basis of the excitation spectrum in the range of 560–580 nm. The spectral sequence rules are assigned, and it can be calculated that the symmetric stretching vibration and the bending vibration frequencies of the ${\mathrm{C}}^{1}{\mathrm{B}}_{2}$ state are ${\omega}_{1}=942.9\text{\hspace{0.17em}\hspace{0.17em}}{\mathrm{cm}}^{-1}$, ${\omega}_{2}=369.8\text{\hspace{0.17em}\hspace{0.17em}}{\mathrm{cm}}^{-1}$, and the bending vibration frequencies of the ${\mathrm{A}}^{1}{\mathrm{A}}_{2}$ state are ${\omega}_{2}=493.4\text{\hspace{0.17em}\hspace{0.17em}}{\mathrm{cm}}^{-1}$. The analysis of the time-resolved spectrum proved that the relaxation process, ${\mathrm{C}}^{1}{\mathrm{B}}_{2}\to {\mathrm{A}}^{1}{\mathrm{A}}_{2}\to {\mathrm{X}}^{1}{\mathrm{A}}_{1}$, and the phosphorescent process, ${\mathrm{a}}^{3}{\mathrm{B}}_{1}\to {\mathrm{X}}^{1}{\mathrm{A}}_{1}$, exist simultaneously.

© 2017 Optical Society of America

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