High-Resolution Absorptive NMR Spectroscopy In Inhomogeneous Magnetic Fields

High-resolution nuclear magnetic resonance (NMR) spectroscopy, which has been widely used in many fields such as physics, chemistry, biology and medicine, offers an effectively noninvasive method to obtain molecular information in biological tissues. In conventional liquid high-resolution NMR experiments, the highly homogeneity of magnetic field is typically required. In many cases, however, homogeneous field is virtually impossible to obtain because of the inherent heterogeneity of the samples and some unideal circumstances. Intermolecular multiple-quantum coherences (iMQCs) originating from distant dipolar interactions between spins just rely on the relative homogeneity of magnetic field within the dipolar correlation distance. Therefore, iMQC can be used to acquire high-resolution NMR spectroscopy in inhomogeneous fields. Now there are few methods used to acquire high-resolution iMQC absorption spectrum. We propose a new method which can obtain absorption spectrum under inhomogeneous fields in this thesis. The main work of this thesis is summarized as follows:1. Firstly, the development history of iMQC were briefly introduced, then we mainly discussed theoretical treatment of iMQCs from CRAZED pulse sequence. The theories of iMQC include classical, quantum, quantum-classical treatment.2. We summarized a variety of iMQC methods and gave some application examples for these methods in biological tissues or in vivo. The applications of intermolecular zero-quantum coherence (iZQC), iZQC combined with localization technique, intermolecular single-quantum coherence (iSQC), intermolecular double-quantum coherence (iDQC) were introduced by sort. High-resolution iMQC technique is a promising method.3. A new pulse sequence termed CT-iDH-iZDQC was proposed. CT-iDH-iZDQC sequence based on the difference of iZQC and iDQC refocusing moments and the clever use of pulse field gradient achieves simultaneous acquisition of iZQC and iDQC signals in one experiment in inhomogeneous fields for the first time. After processing, high-resolution absorptive iMQC NMR spectroscopy can be obtained. The study indicates that the new pulse sequence is applicable to weakly-coupled and strongly-coupled spin systems. In addition to chemical samples, it is applicable to biological tissue samples. Moreover, the sequence is highly time-efficient.