Rotational, internal rotational, and translational motion of acetic acid and dimethyl sulfoxide in their liquid mixture (with some results for DMSO dissolved in MeOH)

The proton magnetic relaxation rate of DMSO in the mixture 33.3 mole % DMSO + 66.7 mole % CD3COOD has been measured in the temperature range 3.5 < 1000/T < 6.0 K and at six frequencies 6 < ν < 144 MHz. The intramolecular relaxation rate was determined by the aid of the isotopic substitution technique. The rotational correlation time of “the molecule” and the time constant of the internal motion have been extracted from these experimental results. The corresponding measurements were also performed on DMSO in the solvent CD3OD (71 mole %) where no internal motion effect appeared in the temperature dependence of the relaxation rate. Furthermore, proton relaxation rates of the acetic acid methyl group and deuteron relaxation rates of the acid methyl and OD group are reported. Again, the data are given in the temperature range as above and for a number of frequencies. Rotational time correlation functions g(t) for the axid molecule are derived. Finally we present experimental results for the self-diffusion coefficients of both mixture partners DMSO and AcH and of DMSO in the solvent MeOH.