Chapter 3. NMR studies of self-diffusion in liquids

5 NMR studies of self-diffusion in liquids

“…In most experiments an inhomogeneous magnetic field is produced by a magnetic field gradient g controlled externally by suitable gradient coils. In three dimensions the gradient is described by (2) where, i, j, k are unit vectors in the x, y and z-direction of the main field of strength B 0 . The total field at position r is then given by However, for the present purpose, it is initially sufficient that only a z-gradient of magnitude g = gؒk in the direction of the main field is considered.…”

“…More detailed reviews of experimental methods for measuring self-diffusion coefficients can be found in the textbooks and articles quoted in the Introduction to this review, and in the preceding review in this series. 2 Techniques for measuring flow processes were not covered in the preceding report. 2 A tutorial introduction to techniques for measuring liquid flow was given in 1978 by Singer.…”

“…This review deals with nuclear magnetic resonance (NMR) studies of diffusive motions and some closely related transport processes in liquids, updating and extending a preceding review in this series. 2 In the absence of external forces, the displacements of the particles result from their thermal agitation. This is an incoherent process leading to random motions of the particles in any state of aggregation.…”

“…Nowadays, this process is usually denoted as selfdiffusion. [1][2][3] It may however be noted that even in the limited field of liquid diffusion, different scientific communities have developed their own terminology 3, 4 which may differ from that used here. † NMR spin-echo experiments provide a series of methods for studying translational motions in liquids by energy-, time-and spatially-resolved experiments.…”

“…The quantity of central interest is the self-diffusion coefficient D which in threedimensional space is related to the mean square displacement of the constituent particles after time t via the Einstein relation [1][2][3] Here r(τ) describes the location of a particle at time τ = 0 and t, respectively, and the brackets 〈. .…”