File:J-coupling Fermi contact mechanism.svg

Page contents not supported in other languages.
This is a file from the Wikimedia Commons
From Wikipedia, the free encyclopedia

Original file ‎(SVG file, nominally 865 × 347 pixels, file size: 3 KB)

Summary

Description
English: Fermi interaction of NMR.

Green arrow: nuclear spin ±½.

Blue arrow: electron spin ±½.

1: Direct J-coupling in hydrogen gas. +½ spin 1H polarizes electron close to it to -½ spin state. Antiparallel spins can exist within the same orbital as described by Pauli exclusion principle. Following the same principle, this -½ electron polarizes the other σ-bond electron to +½ state. +½ electron polarizes 1H nucleus to -½ state. 1H nuclei are now coupled and antiparallel. Coupling constant is positive. As gyromagnetic ratio γ>0 for 1H nuclei, magnetic moment vectors μ are also antiparallel. μ of one nucleus is aligned withe magnetic field of the other nucleus. This is also energeticilly favorable in addition to spin antiparallel alignment.

2: 1H nuclei are parallel. This form is more unstable (has higher energy E) than the form 1. So, E1 < E2.

3: Positive vicinal J-coupling of 1H nuclei via 12C or 13C nuclei. Electron spins on p-orbitals of the carbons are parallel as described by Hund's rules (orbitals are filled with parallel spins).

Sources for the description and the adapted pictures:

  • RS Macomber: A complete introduction to modern NMR spectroscopy. p. 135 John Wiley & sons, Inc., 1998. ISBN 9780471157366
  • M Balcı: Basic ¹H- and ¹³C-NMR spectroscopy. p. 103-105 Elsevier, 2005. OCLC: 162130159. ISBN 9780444518118
Date
Source Own work
Author Keministi

Licensing

I, the copyright holder of this work, hereby publish it under the following license:
Creative Commons CC-Zero This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.

Captions

Add a one-line explanation of what this file represents

Items portrayed in this file

depicts

inception

17 November 2018

File history

Click on a date/time to view the file as it appeared at that time.

Date/TimeThumbnailDimensionsUserComment
current08:52, 17 November 2018Thumbnail for version as of 08:52, 17 November 2018865 × 347 (3 KB)5-HT2ARUser created page with UploadWizard
The following pages on the English Wikipedia use this file (pages on other projects are not listed):

Global file usage

The following other wikis use this file:

Metadata

This file contains additional information, probably added from the digital camera or scanner used to create or digitize it.

If the file has been modified from its original state, some details may not fully reflect the modified file.

Retrieved from "https://en.wikipedia.org/wiki/File:J-coupling_Fermi_contact_mechanism.svg"