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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 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: Nuclear Spin State Population Distribution01:14

Atomic Nuclei: Nuclear Spin State Population Distribution

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.
¹H NMR Signal Multiplicity: Splitting Patterns01:13

¹H NMR Signal Multiplicity: Splitting Patterns

When protons A and X are coupled, their nuclear spin energy levels are slightly modified. This is because the energy required to excite proton A to a spin state parallel to proton X is slightly different from the energy required for it to become anti-parallel to spin X. Consequently, there are two possible excitation frequencies for A (A1 and A2), depending on the spin state of X, and vice versa. The mutual nature of coupling implies that the difference between frequencies A1 and A2, indicated...
Interpreting ¹H NMR Signal Splitting: The (n + 1) Rule01:10

Interpreting ¹H NMR Signal Splitting: The (n + 1) Rule

In the AX proton spin system, proton A can sense the two spin states of a coupled proton X, resulting in a doublet NMR signal with two peaks of equal (1:1) intensity. When proton A is coupled to two equivalent protons (AX2 spin system), the spin states of each X can be aligned with or against the external field, creating three possible scenarios. This results in a 1:2:1  triplet signal, where the central peak corresponds to the chemical shift of A and is twice as large or intense as the others.
Thomson's e/m Experiment01:19

Thomson's e/m Experiment

In a beam of charged particles created by a heated cathode, the particles move at different speeds. However, many applications need a beam with uniform particle speeds. An arrangement known as a velocity selector uses electric and magnetic fields to pick particles with a particular speed from the beam.
A particle with charge q, speed v, and mass m enters an area from the top, where the magnetic and electric fields are perpendicular both to the particle's motion and to one another. The magnetic...

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関連する実験動画

Updated: Jul 8, 2026

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow
13:02

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

Published on: February 27, 2016

超流体3He-Aにおける二重量子渦

Blaauwgeers1, Eltsov, Krusius

  • 1Low Temperature Laboratory, Helsinki University of Technology, Finland.

Nature
|April 13, 2000
PubMed
まとめ
この要約は機械生成です。

研究者らは,超流体ヘリウム-3の二重量子化された渦線の直接的証拠を提供している. 量子システムにおいて極めて重要なこれらのトポロジカルな欠陥は,独特の連続した構造を示し,周期的に形成され,量子化された渦に関する以前の理解に挑戦しています.

さらに関連する動画

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
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Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

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Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
05:51

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method

Published on: July 19, 2019

関連する実験動画

Last Updated: Jul 8, 2026

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow
13:02

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

Published on: February 27, 2016

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
10:42

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

Published on: May 3, 2019

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
05:51

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method

Published on: July 19, 2019

科学分野:

  • 凝縮物質物理学 凝縮物質物理学
  • 量子流体 量子流体とは
  • トポロジカル・デフェクト トポロジカル・デフェクト

背景:

  • 線形欠陥,例えば宇宙弦や量子化された流動線は,様々な物理系において一般的です.
  • 量子化された渦の線は,典型的には単一の量子化 (n=1) であり,超流体やボース・アインシュタイン凝縮体では一般的です.
  • 理論的予測は,超流動的ヘリウム-3-Aの連続構造を持つ二重定量化 (n=2) 渦線の可能性を示唆した.

研究 の 目的:

  • 超流体ヘリウム-3-A.における予測された二重定量化された渦線の存在と性質を実験的に検証する.
  • これらの新しいトポロジカルな欠陥の構造と形成メカニズムを特徴付ける.

主な方法:

  • 高解像度核磁共振 (NMR) 測定を用いたものです.
  • 超流体ヘリウム-3-Aの渦線の形成と振る舞いを観察した.

主要な成果:

  • 直接的な実験的な証拠は,超流体ヘリウム-3-Aで最も一般的な渦線が,確かに2倍量子化されていることを確認しています (n=2).
  • 観測された渦の線は連続した構造を示し,順序パラメータの方向性はスムーズに変化します.
  • 渦の線形成は,ジョセフソン効果の相転移に類似した,規則的で周期的なプロセスで起こります.

結論:

  • この研究は,超流体ヘリウム-3-Aの二重量子化された渦線の最初の直接的な証拠を提供します.
  • これらの発見は理論的予測を検証し,量子流体におけるトポロジカル・デフェクトの振る舞いに関する新しい洞察を提供します.
  • 周期的形成のメカニズムは,これらの複雑な量子構造の新たなダイナミクスを示唆しています.