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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
Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic Nuclei: Nuclear Relaxation Processes

1.1K
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis.
1.1K
Atomic Nuclei: Nuclear Spin State Overview01:03

Atomic Nuclei: Nuclear Spin State Overview

1.8K
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...
1.8K
Atomic Nuclei: Nuclear Spin01:08

Atomic Nuclei: Nuclear Spin

5.1K
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...
5.1K
Nuclear Stability03:18

Nuclear Stability

20.3K
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...
20.3K
Atomic Nuclei: Nuclear Magnetic Moment00:59

Atomic Nuclei: Nuclear Magnetic Moment

3.0K
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...
3.0K

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関連する実験動画

Updated: Apr 22, 2026

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures
08:53

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

Published on: October 9, 2012

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核物理学. 核物理学. 核物理学について. 不均衡なフェルミ系におけるモメンタムシェアリング

O Hen1, M Sargsian2, L B Weinstein3

  • 1Tel Aviv University, Tel Aviv 69978, Israel. or.chen@mail.huji.ac.il.

Science (New York, N.Y.)
|October 18, 2014
PubMed
まとめ

短距離相互作用は,原子核で高モメントの中性子・陽子ペアを生成する. これにより,陽子は中性子に富んだ原子核で中性子よりもモメンタムが高くなり,相互作用なしでは予想に反する.

さらに関連する動画

Setting Limits on Supersymmetry Using Simplified Models
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Setting Limits on Supersymmetry Using Simplified Models

Published on: November 15, 2013

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Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving
11:21

Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving

Published on: March 30, 2017

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関連する実験動画

Last Updated: Apr 22, 2026

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures
08:53

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

Published on: October 9, 2012

17.3K
Setting Limits on Supersymmetry Using Simplified Models
07:46

Setting Limits on Supersymmetry Using Simplified Models

Published on: November 15, 2013

8.2K
Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving
11:21

Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving

Published on: March 30, 2017

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科学分野:

  • 核物理学 核物理学とは
  • 量子クロモダイナミクスは,量子クロモダイナミクスの
  • 天体物理学的な核

背景:

  • 原子核は陽子と中性子 (フェルミオン) を含む.
  • パウリ排除原理は,相互作用がない場合にフェルミオン運動量分布を規定する.
  • 中性子に富んだ原子核では,中性子は通常,陽子よりも高い平均運動量を持っています.

研究 の 目的:

  • 原子核におけるフェルミオンのモメンタム分布を調査する.
  • 短距離相互作用が核運動量に与える影響を決定する.
  • 核構造と中性子星への影響を調査する.

主な方法:

  • 高エネルギー電子散乱実験.
  • 利用対象は,炭素12,アルミニウム27,鉄56,鉛208でした.
  • フェルミオン運動量分布の分析. フェルミオン運動量分布の分析.

主要な成果:

  • 重原子核における短距離のニュクレオン・ニュクレオン相互作用を観測した.
  • 高いモメントの相関する中性子-陽子ペアを特定した.
  • 陽子は中性子よりも,中性子に富んだ原子核でフェルミ・モメントを上回る可能性が高いことが判明した.

結論:

  • 短距離相互作用は,原子核におけるフェルミオン運動量分布を大幅に変化させます.
  • プロトン・ニュートロン相関は,単純な核モデルに挑戦する.
  • この発見は,核天体物理学や超冷たい原子ガスの研究にも関連しています.