Method for nuclear magnetic resonance (NMR) spectroscopy measurements using long-lived coherences (LLC)
A method for nuclear magnetic resonance (NMR) spectroscopy of a sample comprises preparation of the sample and carrying out an NMR spectroscopy measurement. Preparation includes excitation of long lived coherences (LLC) between the singlet state S0 and the central triplet state T0 of nuclei of the sample. The thermal equilibrium Boltzmann distribution (Iz+Sz) is thereby transformed into a difference (Iz-Sz), which is flipped to the transverse plane, and irradiation of the sample with an rf-field is initiated. The LLC is sustained by maintaining the rf-irradiation during an interval t1 and the LLC is converted into observable magnetisation by interrupting the rf-irradiation. The method allows nuclear magnetic resonance spectroscopy measurements with improved spectral resolution.