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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...
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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.
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Atomic Nuclei: Nuclear Spin01:08

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All atomic particles possess an intrinsic angular momentum, or 'spin'. Electrons, protons, and neutrons each have a spin value of ½, although protons and neutrons in nuclei may have higher half-integer spins owing to energetic factors.
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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...
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The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved...
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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.
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Longitudinal target-spin asymmetries for deeply virtual compton scattering.

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Area of Science:

  • Nuclear Physics
  • Particle Physics
  • Quantum Chromodynamics

Background:

  • Deeply inelastic scattering experiments probe the internal structure of protons.
  • Generalized Parton Distributions (GPDs) offer a framework to understand nucleon structure.
  • Target-spin asymmetries in deeply virtual Compton scattering are sensitive to GPDs.

Purpose of the Study:

  • To measure target-spin asymmetries in the electroproduction of photons off protons.
  • To probe the spatial distribution of the proton's axial charge using generalized parton distributions.
  • To constrain existing parametrizations of chiral-even generalized parton distributions.

Main Methods:

  • Used a nearly 6 GeV electron beam at Jefferson Lab.
  • Employed a longitudinally polarized proton target and the CEBAF Large Acceptance Spectrometer.
  • Analyzed ep→e^{'}p^{'}γ events, extracting asymmetries over a wide kinematic range.

Main Results:

  • Extracted target-spin asymmetries for deeply virtual Compton scattering (DVCS) and Bethe-Heitler interference.
  • Investigated the t dependence of asymmetries, indicating axial charge concentration at the proton's center.
  • Covered the widest kinematics in Q^{2}, x_{B}, t, and ϕ for 166 four-dimensional bins.

Conclusions:

  • The spatial distribution of the proton's axial charge is concentrated in its center.
  • Results provide crucial constraints for theoretical models of generalized parton distributions.
  • Advances understanding of the proton structure in the deeply inelastic regime.