Molecular constants of SiF4, GeF4, and RuO4: An improvement of the analysis of the ir-band contours of ν3(F2) by low temperature measurements and by using isotopically pure compounds

The ir-band contour of ν₃(F₂) of gaseous SiF₄, GeF₄, and RuO₄ have been analyzed making use of isotope substitution techniques, low temperature measurements, and matrix isolation spectroscopy. In the case of RuO₄ values for the hot band progression ν₃ + nν₄ ? nν₄ (X₃₄ = ?1.1 ± 0.1 cm^?1 for ⁹⁹RuO₄ and ¹⁰⁴RuO₄) have been obtained and F₂ block force constants have been calculated using isotope shifts Δω₃ and ζ₃ constants as additional data.