Pau Nolis

The concept of the acquisition of multiple free induction- decay signals within the same scan allows the obtention of complementary NMR spectroscopic data within the same scan, thus optimizing spectrometer time.

Such periods can be understood as simple evolution or relaxation delays and can therefore be implemented in a variety of applications. Under optimum relaxation conditions, multiple FID periods can be incorporated whenever enough longer periods (around 80–100 ms) are available. Experimentally, it is important to find an optimum balance between FID duration and digital resolution.

Time-Shared evolution makes  possible to obtain a number of different NMR spectra by the simultaneous detection of independent coherence pathways. Typical heteronuclear NMR spectroscopic experiments used for small and medium-sized molecules, such as HSQC or HMBC, can be recorded simultaneously for two different nuclei, typically 13C and 15N). 

Considerable savings can be made in the time required to record the spectra when compared to the separate acquisition of individual spectra.

The determination of both the magnitude and the sign of heteronuclear coupling constants is fundamental in the structural characterization of organic, organometallic, and inorganic compounds.

Scalar Coupling constants J allow one to trace out homonuclear/heteronuclear through-bond connectivities and their quantification yields information about dihedral angles for 3J via well-known Karplus relationships. 

Measurements of Residual Dipolar Coupling constants RDCs in partially oriented small molecules dissolved in weakly aligned anisotropic media allow to obtain 3D structural information based on the relative orientations of molecular bonds (vectors).

Over recent years, a significant interest has emerged to develop homodecoupled 1H NMR spectroscopy techniques, also known as Pure Shift NMR. These recent advances offer increased resolution by simplifying the homonuclear splitting pattern, and therefore reducing signal overlapping. However, the methodologies suffers from the sensitivity point of view.

From the application point of view Pure Shift strategies have been incorporated to many routine NMR experiments and its evaluation and success is in continuous evolution. 

Spectral Aliasing offers an extraordinary high digital resolution along the indirect dimension by using a reduced spectral width. 

Implementation and evaluation of this technique in different NMR experiments and samples of different nature is of current interest in our group.