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相关概念视频

Mass Spectrometry: Isotope Effect01:13

Mass Spectrometry: Isotope Effect

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Most elements exist in nature as a mixture of isotopes. The isotopes differ in weight due to their respective number of neutrons. The molecular weight of a molecule is different depending on the specific isotope of its elements involved. As a result, the mass spectrum of the molecule exhibits peaks from the same fragment at multiple positions. The positions of these mass signals depend on the difference between the molecular mass. Furthermore, the intensity of these signals is dependent on the...
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Isotopes01:12

Isotopes

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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,...
57.0K
Isotopes and Radioisotopes01:28

Isotopes and Radioisotopes

8.7K
In the early 1900s, English chemist Frederick Soddy realized that an element could have atoms with different masses that were chemically indistinguishable. These different types are called isotopes — atoms of the same element that differ in mass. Isotopes differ in mass because they have different numbers of neutrons but are chemically identical because they have the same number of protons. Soddy was awarded the Nobel Prize in Chemistry in 1921 for this discovery.
An isotope containing...
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¹H NMR of Labile Protons: Deuterium (²H) Substitution00:48

¹H NMR of Labile Protons: Deuterium (²H) Substitution

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This lesson illustrates the role of deuterium substitution in simplifying the NMR spectrum of compounds comprising labile protons. One method employed is the use of deuterium. Amongst the three isotopes of hydrogen, deuterium (2H) has a nucleus composed of one proton and one neutron. When the D2O solvent is added to a pure dry ethanol solution, its labile proton is substituted with deuterium.
932
Nuclear Overhauser Enhancement (NOE)01:07

Nuclear Overhauser Enhancement (NOE)

757
Irradiation of a spin-active nucleus causes an increase or decrease in the signal intensity of neighboring nuclei that are not necessarily chemically bonded or involved in J-coupling.  This phenomenon, called the Nuclear Overhauser Enhancement (NOE), results from through-space interactions between the nuclear spins. The NOE effect decreases with increasing internuclear distance and is generally not observed beyond 4 angstroms. In NOE, dipole-dipole interactions between neighboring...
757
Atomic Nuclei: Nuclear Spin State Population Distribution01:14

Atomic Nuclei: Nuclear Spin State Population Distribution

1.0K
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.
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Electrochemical Detection of Deuterium Kinetic Isotope Effect on Extracellular Electron Transport in Shewanella oneidensis MR-1
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在 D 中的同位素效应 D.

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概括
此摘要是机器生成的。

研究H2O/D2O与碰撞中的电子转移,揭示了能量依赖的分支比和同位素效应. 这项研究首次确定了D2O的D-O键解离能.

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科学领域:

  • 物理化学 物理化学
  • 化学物理 化学物理
  • 原子和分子碰撞 原子和分子碰撞

背景情况:

  • 了解分子中的电子转移过程对于化学动力学至关重要.
  • 水 (H2O) 和它的同位素 (D2O) 是化学和物理学的基本分子.
  • 研究离子-分子反应为分子电子结构提供了洞察力.

研究的目的:

  • 为了研究H2O/D2O与中性碰撞中的电子转移过程.
  • 为了确定分支比和同位素效应的能量依赖性.
  • 描述所涉及的电子状态和键解离能.

主要方法:

  • 来自H2O/D2O与碰撞的负离子 (OH-/OD-, O-, H-/D-) 的飞行时间质谱.
  • 在205 eV的冲击能量下,离子能量损失光谱.
  • 在K-H2O/D2O系统中对未被占用的分子轨道进行量子化学计算.

主要成果:

  • 观察到OH-/OD-,O-,和H-/D-负离子,具有能量依赖的分支比.
  • 在D2O碰撞中观察到显著的同位素效应.
  • 确定D2O的D-O键解离能量为5.41 ± 0.10 eV.
  • 通过量子化学计算支持实验发现,识别涉及的电子状态.

结论:

  • H2O/D2O与的电子转移碰撞显示出显著的能量依赖和同位素效应.
  • 该研究提供了第一个在D2O中D-O键解离能量的实验性确定.
  • 碰撞动态阐明了K-H2O/D2O系统中单双激发分子轨道的性质.