Eric Picquenard

Raman spectra of overheated sulfur vapor

Abstract Our thermodynamic study allows to confirm the selective observation with a blue exciting line (457.9 or 476.5 nm) of the resonance Raman spectra of the S 3 molecule. The extinction coefficient of the maximum λ = 395 nm of its absorption spectrum e = 2100 1 mole −1 cm −1 is quite lower than that previously reported. The resonance Raman spectra of 32 S 3 and 34 S 4 may be explained with three normal frequencies and confirm the bent C 2v geometry of this molecule in perfect agreement with the structure of the parent anions, S − 3 and S 2− 3 .

Vibrational study and molecular structure of two S4 isomers in sulphur vapour

Raman spectra of sulphur vapour for two pressures (0.1 and 0.2 MPa) and various temperatures up to 700 °C were recorded using several krypton ion and argon ion laser exciting radiation wavelengths. Resonance Raman enhancement effects in conjunction with 32S/34S isotopic effects allow one to distinguish three fundamental vibrational modes (νs, νc, δs) of a green absorbing (λmax = 530 nm) chain-like S4 molecule from the modes belonging to S3 and other cyclic S6, S7 and S8 molecules. Moreover, using a 647.1 nm excitation wavelength, several vibrational modes of another red absorbing (λmax = 560–660 nm) branched-ring S4 isomer were characterized. Finally, normal coordinate treatments confirm the trans planar C2h structure of the chain-like S4 species, whereas a comparison of the observed and calculated wavenumbers for the red absorbing S4 isomer is in agreement with a branched-ring structure. Copyright

Resonance Raman spectra of the S4 molecule in the sulfur vapor

Abstract Raman spectra of sulfur vapor at 620°C under 530.8 nm excitation basically consist of resonance Raman spectra of S4 molecule. Only the three symmetric modes are observed, valence force field calculations confirm the trans planar structure C2h of S4.