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Related Concept Videos

Nuclear Stability03:18

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together in the...
Atomic Nuclei: Nuclear Spin01:08

Atomic Nuclei: Nuclear Spin

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.
Atomic nuclei have a net nuclear spin, , which can have an integer or half-integer value. In atomic nuclei, the spins of protons are paired against each other but not with neutrons, and vice versa. Consequently, an even number of protons does not contribute to...
Atomic Nuclei: Nuclear Magnetic Moment00:59

Atomic Nuclei: Nuclear Magnetic Moment

All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2 + 1 orientations. A hydrogen nucleus, which is just a...
Atomic Nuclei: Nuclear Spin State Overview01:03

Atomic Nuclei: Nuclear Spin State Overview

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...
Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
Other Nuclides: 31P, 19F, 15N NMR01:16

Other Nuclides: 31P, 19F, 15N NMR

Many organic, inorganic, and biological molecules contain spin-half nuclei such as nitrogen-15, fluorine-19, and phosphorus-31. As a result, NMR studies of these nuclei have found extensive applications in chemical and biological research.
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...

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Visualization of miniSOG Tagged DNA Repair Proteins in Combination with Electron Spectroscopic Imaging (ESI)
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'Magic' nucleus 42Si.

J Fridmann1, I Wiedenhöver, A Gade

  • 1Department of Physics, Florida State University, Tallahassee, Florida 32306-4350, USA.

Nature
|June 17, 2005
PubMed
Summary
This summary is machine-generated.

Nuclear shell structures influence atomic nuclei stability. In neutron-rich 42Si, researchers found evidence of a proton subshell closure and a nearly spherical shape, challenging existing nuclear models.

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Area of Science:

  • Nuclear Physics
  • Atomic Nuclei Structure
  • Quantum States

Background:

  • Nuclear shell structures, defined by proton and neutron quantum states, are key to atomic nuclei stability.
  • Nuclei with 'magic numbers' of protons/neutrons exhibit enhanced stability due to closed shells.
  • The stability and potential shape deformations of neutron-rich nuclei remain an open fundamental question.

Purpose of the Study:

  • Investigate nuclear shell effects in the neutron-rich 42Si nucleus.
  • Determine if magic numbers and shell closures persist in exotic, neutron-rich isotopes.
  • Explore the shape and proton subshell structure of 42Si.

Main Methods:

  • Utilized one- and two-nucleon knockout reactions.
  • Employed beams of exotic nuclei for measurements.
  • Studied 42Si and neighboring nuclei.

Main Results:

  • Presented strong evidence for a proton subshell closure at Z=14 (14 protons).
  • Observed near degeneracy of two distinct proton orbits (s(1/2) and d(3/2)) near 42Si.
  • Indicated a nearly spherical shape for the 42Si nucleus.

Conclusions:

  • The findings suggest a well-developed proton subshell closure at Z=14 in 42Si.
  • The observed proton orbital structure and shape provide insights into nuclear stability in neutron-rich isotopes.
  • This study contributes to understanding the evolution of nuclear shell structure far from stability.