Contribution to the Study of Electronic Spectra of Bent Triatomic Molecules

Abstract

The electronic absorption spectra of the SO₂, SeO₂, and TeO₂ molecules have been studied under widely varied experimental conditions. The vibrational analysis of the ultraviolet absorption region of SO₂ with center of gravity near 2000A reveals that it is formed by at least two electronic systems with the following vibrational constants: $$\begin{array}{c}\mathrm{System}{\mathrm{\hspace{0.17em}\alpha }}_1{\mathrm{···\nu }}_0\text{=42,170\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\hspace{0.17em}\hspace{0.17em}\nu }}_1^{\prime }\text{=963\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\hspace{0.17em}\hspace{0.17em}\nu }}_2^{\prime }\text{=379\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\hspace{0.17em}\hspace{0.17em}x}}^{\prime }{\nu }_2^{\prime }\text{=2\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}.\\ \mathrm{System}{\mathrm{\hspace{0.17em}\alpha }}_2{\mathrm{···\nu }}_0\text{=44,236\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\hspace{0.17em}\hspace{0.17em}\nu }}_1^{\prime }\text{=775\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}{\mathrm{,\hspace{0.17em}\hspace{0.17em}\nu }}_2^{\prime }\text{=375\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}.\end{array}$$ The presence in the same region of a third electronic system, with ν₂′=360 cm⁻¹ and ν₁′=845 cm⁻¹, seems highly probable. The character of the vibrational structure of the band systems and a preliminary analysis of the rotational structure of several bands have enabled us to obtain some information about the molecular structure of the excited states. The vibrational analysis of the c‐system of SeO₂ in the visible, and the TeO₂ bands in the visible and ultraviolet, have enabled us to correlate the electronic states of the three similar molecules.