関連する実験動画
Updated: Jul 12, 2026

10:42
Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
Published on: May 3, 2019
まとめ
原子核の構成要素であるニュクレオンは,信じられないほど安定しています. この研究は,テルリウム-130の核子平均寿命の新しい下限値である1.6 x 10^25年を設定し,以前の限界値を大幅に改善した.
科学分野:
- 核物理学 核物理学とは
- 素粒子物理学 素粒子物理学について
- 地質化学 地質化学
背景:
- 核子 (陽子と中性子) の安定性は,物理学における基本的な概念である.
- 以前の実験では,様々な方法によって,核子寿命の限界が確立されていた.
- バリオン数の保存は,粒子物理学の標準モデルにおける重要な原理であるが,いくつかの理論は,その違反を予測している.
研究 の 目的:
- 原子核の平均寿命のより厳格な下限を確立する.
- バリオン数保存の潜在的な違反を調査するために.
- 基本粒子特性の制約のために地球化学データを活用する.
主な方法:
- 公開された地化学データの分析.
- 古代のテルリド鉱石内のクセノン同位体の測定.
- 観測されたクセノンイソトープに基づいて,ヌクレオン崩壊速度の計算.
主要な成果:
- テルリウム-130核の核の平均寿命の下限である1.6 x 10^25年が決定されました.
- この限界は,特定の核子崩壊モードとは無関係です.
- 新しい制限は,以前の厳格な制限よりも約2桁強くなっています.
結論:
- この発見は,潜在バリオン数の非保存に関する厳格な制約を提供する.
- この研究は,基礎物理学の探査のための地球化学分析の有用性を実証しています.
- 核子の安定性は,これらの強化された実験限界によってさらに強化されます.
関連する概念動画
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...
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The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect indicates a “loss” in mass of 4.0331 amu – 4.0026 amu = 0.0305 amu. The loss in mass accompanying the formation of an atom from protons, neutrons, and electrons is due to the conversion of that mass into energy that is evolved as the atom forms. The nuclear binding energy is the energy produced when the atoms’ nucleons are bound together;...
Radioactivity and Nuclear Equations
Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for hydrogen, neutrons. The number of protons in the nucleus is called the atomic number (Z) of the element, and the sum of the number of protons and the number of neutrons is the mass number (A). Atoms with the same atomic number but different mass numbers are isotopes of the same element.
A nuclide of an element has a specific number of protons and...
A nuclide of an element has a specific number of protons and...
Isotopes
Elements have a set number of protons that determines their atomic number (Z). For example, all atoms with eight protons are oxygen; however, the number of neutrons can vary for atoms of the same element. The sum of the number of protons and the number of neutrons is the mass number (A). Atoms with the same atomic number but different mass numbers are called isotopes. Elements can have multiple isotopes, for example, carbon-12, carbon-13, and carbon-14.An element's atomic mass, or weight, is a...
Atomic Nuclei: Nuclear Relaxation Processes
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. This...
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.

