Knowledge Bank

The infrared absorption by four isotopic forms of neat liquid methanol has been measured by attenuated total reflection and transmission methods. As has been described for $CH3OH$ and $CH3OD1,2$. The measurements were converted to spectra of the real and imaginary refractive index, the optical constants, and then to spectra of the imaginary molar polarizability or its close relative the susceptibility. The absorption measurements are believed to be accurate to about 3%. The spectra of the different isotopic forms allow the contributions to the intensity from different vibrations to be separated with unusually high confidence, and we believe the integrated intensities of the different vibrations are known to a few present. The integrated intensities and transition moments will be reported, the effect of isotope on the intensities will be noted, and the use of double harmonic theory to obtain dipole moment parameters for these liquid-phase molecules will be discussed.