相关实验视频
Updated: Jan 9, 2026

07:46
Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
8.9K
限制最轻的p核的合成 ^{74}Se
A Tsantiri1,2,3, A Spyrou1,2, E C Good1
1Michigan State University, Facility for Rare Isotope Beams, East Lansing, Michigan 48824, USA.
Physical review letters
|December 5, 2025
概括
这项研究测量了{73}Asp,γ) ^{74}Se反应速率,这对于理解{74}Se在恒星中的产生至关重要. 结果表明,仅核物理学无法解释超新星中观察到的超产量.
科学领域:
- 核天体物理学 核天体物理学
- 恒星核合成 恒星核合成
- 爆炸性的恒星环境
背景情况:
- 重元素的起源,特别是像Se这样的p核,仍然是天体物理学中的一个关键问题.
- ^{73}As(p,γ) ^{74}Se反应是在恒星爆炸期间的玛 (γ) 过程中对Se是一个重要的破坏途径.
- 之前的研究缺乏对这种特定反应截面的实验数据.
研究的目的:
- 通过实验确定^{73}As(p,γ) ^{74}Se反应的截面.
- 为了限制反应速度,影响在爆炸性恒星环境中的Se丰度.
- 研究这种反应在产生p核中的作用.
主要方法:
- 使用了放射性 ^{73} 作为在特定质量中心能量 (2.9 和 2.3 MeV/核子) 的束.
- 测量了 ^{73}As(p,γ) ^{74}Se反应的总截面.
- 提取了Se化合物核的统计性质.
- 执行蒙特卡罗单区网络模拟,以评估对Se生产的影响.
主要成果:
- 提供了第一个实验性截面,用于{73}As{p,γ) ^{74}Se反应.
- 限制了与 γ 过程相关的高层 Gamow 窗口内的反应截面.
- 模拟表明,仅靠核物理无法解决II型超新星中Se的过度产量.
结论:
- 对{73}Asp,γ) ^{74}Se反应的实验数据对于完善恒星模型至关重要.
- 在II型超新星中观察到的Se过度产量可能需要对天体物理条件有更深入的了解.
- 对过程及其环境依赖性的进一步研究是有必要的.
相关概念视频
Nuclear Transmutation
20.4K
Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with another particle. The first manmade nucleus was produced in Ernest Rutherford’s laboratory in 1919 by a transmutation reaction, the bombardment of one type of nuclei with other nuclei or with neutrons. Rutherford bombarded nitrogen-14 atoms with high-speed α particles from a natural radioactive isotope of radium and observed...
20.4K
Nuclear Stability
22.8K
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...
To hold positively charged protons together...
22.8K
Nuclear Binding Energy
14.6K
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...
14.6K
Other Nuclides: 31P, 19F, 15N NMR
705
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...
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...
705
Nuclear Fusion
33.6K
The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process called fusion. The principal source of energy in the sun is a net fusion reaction in which four hydrogen nuclei fuse and ultimately produce one helium nucleus and two positrons.
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...
33.6K
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)
969
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT) is an advanced Nuclear Magnetic Resonance (NMR) technique specifically designed to detect and enhance the signals of low-abundance nuclei, such as carbon-13 and nitrogen-15, in small molecules. The fundamental principle behind INEPT is the transfer of polarization from a more abundant and highly polarizable nucleus, typically hydrogen-1, to the low-abundance nucleus of interest. This process effectively boosts the NMR signal of the...
969

