Dependence of theF19Nuclear Resonance Position on Chemical Compound

Peer Reviewed: NMR Spectroscopy: Past and Present

“…By accident, they had discovered the chemical shift. About the same time, Dickinson noticed similar effects for 19 F in several compounds, and Arnold, Dharmatti, and Packard observed separate resonances for the -CH 3 , -CH 2 -, and -OH protons of ethanol ( Figure 1) (7,8). Arnold and colleagues also observed that the relative intensities of the resonances were the same as the relative numbers of protons.…”

T 2 : The Transverse Relaxation Time

“…The chemical shift effect is a result of the variation in the motion of bound electrons owing to an interaction with B 0 (Harris, 1986;Dickinson, 1950;Proctor and Yu, 1950). As a result, the magnetic field experienced by the corresponding nucleus changes by a small amount.…”

“…However, if the direction of the applied gradient is reversed, the signal will refocus, but the effects of any inhomogeneities in the main B 0 field (caused for example by imperfections in the magnet or by susceptibility inhomogeneity at air-tissue interfaces or from the presence of paramagnetic or ferromagnetic substances), as well as dephasing effects caused by the chemical shift effect (Harris, 1986;Dickinson, 1950;Proctor and Yu, 1950), will still be present and the resulting echo peak will be attenuated by T 2 * . In addition, if the field inhomogeneity is such that the stray gradient introduced is large over a small volume element, a significant signal loss will occur owing to the dephasing of isochromats within this volume, resulting in a considerable reduction in T 2 * .…”

Nuclear Magnetic Resonance and Electron Spin Resonance Spectroscopy: Introduction

“…However, within a few years, it was discovered that NMR absorption not only depends on the magnetogyric ratio of the nucleus but also slightly on the local electronic environment, a phenomenon known as the magnetic shielding (often codified by the parameter known as the chemical shift). (6)(7)(8) Similarly, the electron g factor depends on chemical identify and provides a means to identify chemical structure.…”