关键词: 多重自旋回波峰, 高温近似, 分子间多量子相干, 去磁场

Abstract:

A large body of conspicuous publications in recent years asserts that the high t emperature approximation (HTA), a mostly tested and most widely used assumption  in NMR spectroscopy and MRI technology, is invalid for concentrated samples in h igh magnetic fields such as for a proton COSY spectrum of water. A by-product o f  the alleged collapse of HTA, which is equally surprising, is the existence of i ntermolecular multi-quantum-coherences (MQC) in low viscosity liquids such as  wa ter. In this work, both HTA and intermolecular MQCs in liquids will be criticall y examined in light of our theoretical analysis and experimental results. Our co nclusions are: (1) There are no macroscopic quantum systems in conventional NMR samples such as water at room temperature. (2) At room temperature, high tempera ture approximation is still one of the most trustworthy approximations applicabl e to NMR and (3) The MQCs observed in proton COSY spectrum in, e.g., water, have  nothing to do with quantum mechanical intermolecular spin interactions.

Key words: multi-spin echoes, high temperature approximation, intermolecular multi-quantum coherences, demagnetization field