Pressure and temperature dependence of the longitudinal proton and deuteron relaxation rates in liquid H₂S and D₂S

The pressure and temperature dependence of the spin-lattice relaxation time T1 for the protons in liquid H2S and the deuterons in liquid D2S have been measured between the melting-pressure-curve and 395 K at pressures up to 200 MPa. The different contributions to the experimental relaxation rate T1−1 could be separated with the extended J-diffusion model. The results are compared with analogous measurements made previously in liquid water and liquid ammonia in order to get some insight into the influence of hydrogen bonding interactions upon molecular motions in these liquids. From the pressure dependence of the isotherms an activation volume of Δ V‡ = 2 ± 0.5 [cm3/mol] is derived for the rotational motion of the H2S molecule, while the translational motion is characterized by a higher Δ V‡ = 7 ± 1 [cm3/mol]