Isotope effects in the vibrational spectrum of the SF6 molecule

The IR absorption spectra of solutions of SF6 in liquid argon are studied at a temperature of 93 K in the concentration interval 10−5–10−7 mole fractions. A sample with a natural abundance of isotopes and a monoisotope 34SF6 sample are studied. The frequencies, half-widths, and relative intensities of bands in the vibrational spectrum of all isotopomers of the molecule are determined. For the 34SF6 molecule, the ratio of integral absorption coefficients of fundamental bands A(ν4)/A(ν3)=0.07(6) is larger than 32SF6:A(ν4)/A(ν3)=0.66(4) for the 32SF6 molecule, which corresponds to the same signs of P′3 and P′4. The change in the intensity of the ν2+ν6 and ν5+ν6 bands upon isotopic substitution is explained by the change in the resonance contributions of due to the isotope shift of the ν3 band.