Novel Multidimensional Inverse Laplace Nuclear Magnetic Resonance Spectroscopy Techniques
This thesis presents the new development and application of multidimensional inverse Laplace nuclear magnetic resonance spectroscopy techniques. We present a new NMR technique which relates the longitudinal relaxation rate of the NMR signal to the internal gradients in the sample. We perform the experiment on a large range of magnet strengths to provide experimental evidence for the theory of how internal gradient intensity scales with pore size as a function of field strength. We make the first attempt of quantisation of two dimensional inverse Laplace experiments. We perform a transverse relaxation exchange experiment on several samples for a range of mixing times. We then integrate the peaks in the resulting spectra and plot them as a function of mixing time. By fitting the experimental results to theory, we can estimate the molecular exchange between pores of differing sizes. We then modify the transverse relaxation experiment to include diffusion attenuation so that we can see the separate signals for oil and water. We use this to look at the effect wettability has on the movement of the different fluids between pores. We then present the first experiment to combine two inverse Laplace dimensions with a Fourier dimension. We add a propagator dimension to the transverse relaxation exchange experiment to measure how far the molecules move during the mixing time. Quantisation of the results allows us to estimate the exchange rate between pores of similar sizes in addition the exchange rate between pores of different sizes. We are also able to estimate pore radii, inter-pore spacing and tortuosity. Lastly, we attempt a three dimensional inverse Laplace experiment by correlating transverse relaxation, diffusion, and internal gradients. While the three dimensional inversion techniques require more development, the results show resemblance to those seen from two dimensional experiments.