Nuclear Overhauser effect

Abbreviated as NOE. This phenomenon occurs when two nuclei are spatially close to each other and have a strong dipole interaction, and the resonance of one nucleus is saturated, the signal intensity of the other nucleus increases or decreases. When measuring ^13C NMR, the signal intensity of carbon bonded to hydrogen can be increased by irradiating and saturating the ^1H nucleus (noise decoupling). In addition, since NOE is inversely proportional to the sixth power of the internuclear distance, it is also used in molecular structure analysis. NOESY spectra are the application of this phenomenon to two-dimensional NMR, and signals originating from nuclei that are close in distance are observed as correlation peaks.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

略称NOE．二つの核が空間的に近い位置にあり，双極子相互作用が強いとき，一方の核の共鳴を飽和させると，他方の核のシグナル強度が増加または減少する現象をいう．¹³C NMRの測定の際，¹H 核を照射して飽和させる(ノイズデカップリング)ことにより，水素と結合している炭素のシグナル強度を上げることができる．また，NOEは核間距離の6乗に逆比例するため，分子の構造解析にも利用される．この現象を二次元NMRに適用したのがNOESYスペクトルであり，距離的に近い核に由来するシグナルが相関ピークとして観測される．

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