Ultrafast Intermolecular Zero Quantum Spectroscopy

Gigi Galiana, Rosa T. Branca, and Warren S. Warren

J. Am. Chem. Soc., in press (2005)

Clinical magnetic resonance spectroscopy is typically limited by magnetic inhomogeneities which destroy spectral resolution, but intermolecular zero quantum coherences (iZQCs) are insensitive to such inhomogeneities. iZQC resolution in vivo, however, has been hampered by physiological fluctuations over the time scale of the two-dimensional acquisition. A faster iZQC sequence will allow us to average away these fluctuations, and thus we present a new approach to ultrafast two-dimensional spectroscopy. This communication reports iZQC experiments acquiring up to 31 t1-points per scan, as well as extensions to a broad range of other 2D sequences.

Intermolecular multiple quantum coherences at high magnetic field: The nonlinear regime

J. P. Marques, S. Grant, S. Blackband, R. W. Bowtell
J. Chem. Phys. 123, 164311 (2005) (10 pages)

Experiments have been carried at magnetic-field strengths of 9.4, 14.1, and 17.6 T to explore the evolution of intermolecular multiple quantum coherences in the nonlinear regime where the system evolves for times that are much greater than the characteristic time of action of the long-range dipolar field, _d. The results show the expected Bessel function form of the recorded signal as a function of time of evolution, with evident zeros and sign changes. As expected, the rate of signal evolution increases at higher-field strengths as a result of the increased equilibrium magnetization. A numerical method for calculating the evolution of magnetization under the action of the distant dipolar field, relaxation, and diffusion that is based on Fourier analysis of the magnetization distribution has been applied to the correlated two-dimensional spectroscopy revamped by asymmetric z-gradient echo detection sequence in the nonlinear regime and shown to produce results that are in good agreement with experimental data acquired at different magnetic fields and rates of spatial modulation. Experiments and simulations have also been used to explore the evolution of magnetization in a mixture of two interacting spin species in the nonlinear regime. ©2005 American Institute of Physics

Simultaneous measurement of D and T2 using the distant dipolar field

Wilson Barros, Jr., John C. Gore and Daniel F. Gochberg
Journal of Magnetic Resonance
Article in Press, Corrected Proof

The presence of long-range dipolar fields in liquids is known to introduce a non-linear term in the Bloch–Torrey equations which is responsible for many interesting effects in nuclear magnetic resonance as well as in magnetic resonance imaging. We show here, for the first time, that the diffusion coefficient D and the spin–spin relaxation time T₂ can be obtained simultaneously from the time evolution profile of the long-range dipolar field refocused signal. In a COSY Revamped by Z-asymmetric Echo Detection sequence, the analytical first-order approximation solution of the Bloch–Torrey equations modified to include the effect of the distant dipolar field is used to demonstrate the technique in an experiment using doped water.