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Related Concept Videos

Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

1.2K
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
1.2K
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

1.5K
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
1.5K
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

1.2K
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
1.2K
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

1.3K
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
1.3K
Atomic Nuclei: Nuclear Spin State Overview01:03

Atomic Nuclei: Nuclear Spin State Overview

1.9K
NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of one, the...
1.9K
Atomic Nuclei: Nuclear Spin State Population Distribution01:14

Atomic Nuclei: Nuclear Spin State Population Distribution

1.7K
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
1.7K

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Related Experiment Video

Updated: May 1, 2026

Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser
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Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

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Using geoelectrons to search for velocity-dependent spin-spin interactions.

L R Hunter1, D G Ang1

  • 1Physics Department, Amherst College, Amherst, Massachusetts 01002, USA.

Physical Review Letters
|March 25, 2014
PubMed
Summary

This study bounds long-range spin-spin interactions using a geoelectron-spin model and laboratory data. It significantly improves limits on five previously unbounded interactions and enhances the bound on a sixth by 30 orders of magnitude.

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Area of Science:

  • Particle Physics
  • Astrophysics
  • Geophysics

Background:

  • Electron spins within Earth offer a unique environment to probe fundamental interactions.
  • Previous laboratory experiments set limits on fermion-spin orientations relative to Earth.

Purpose of the Study:

  • To investigate six possible long-range velocity-dependent spin-spin interactions.
  • To constrain interactions mediated by ultralight or massless intermediate vector bosons.

Main Methods:

  • Utilized a recently developed geoelectron-spin model.
  • Combined data from three existing laboratory experiments.
  • Applied the model to experimental results to derive bounds on spin-spin interactions.

Main Results:

  • Established new upper limits for five previously unbounded spin-spin potentials.
  • Improved the bound on the sixth potential by 30 orders of magnitude in the long-range limit.
  • Constrained velocity-dependent interactions coupling electron spin to electron, neutron, and proton spins.

Conclusions:

  • The geoelectron-spin model, combined with experimental data, provides powerful constraints on fundamental spin-spin interactions.
  • This research significantly advances our understanding of potential new forces mediated by light bosons.