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相关概念视频

Nuclear Stability03:18

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...
Radioactive Decay and Radiometric Dating02:48

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. The number of disintegrations per unit time is called the activity (A), which is directly proportional to the number of nuclei in the sample. The decay constant (λ) is an average probability of decay per nucleus in unit time.
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.
Atomic Nuclei: Types of Nuclear Relaxation01:28

Atomic Nuclei: Types of Nuclear Relaxation

Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers energy to a nearby...
Atomic Absorption Spectroscopy: Instrumentation01:22

Atomic Absorption Spectroscopy: Instrumentation

An atomic absorption spectrophotometer (AAS) comprises several components: a radiation source, an atomizer, a monochromator, and a detector. The radiation source can be a hollow-cathode lamp (HCL) or an electrodeless-discharge lamp (EDL), both of which provide a narrow emission line of the required wavelength. However, some instruments use continuum sources and high-resolution monochromators to achieve a narrow range of radiation.
The atomizer used in AAS can be either a flame atomizer or an...
Atomic Emission Spectroscopy: Instrumentation01:22

Atomic Emission Spectroscopy: Instrumentation

The instrumentation of atomic emission spectrometry (AES) involves various components, including atomization devices that convert samples into gas-phase atoms and ions. There are two main types of atomization devices: continuous and discrete atomizers.  Continuous atomizers, like plasmas and flames, introduce samples in a constant stream, while discrete atomizers inject individual samples using syringes or autosamplers. The most common discrete atomizer is the electrothermal atomizer.

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相关实验视频

Updated: May 26, 2026

A Basic Positron Emission Tomography System Constructed to Locate a Radioactive Source in a Bi-dimensional Space
14:19

A Basic Positron Emission Tomography System Constructed to Locate a Radioactive Source in a Bi-dimensional Space

Published on: February 1, 2016

原子短暂记录器 原子短暂记录器

R Kienberger1, E Goulielmakis, M Uiberacker

  • 1Institut für Photonik, Technische Universität Wien, Gusshausstrasse 27, A-1040 Wien, Austria.

Nature
|February 27, 2004
PubMed
概括
此摘要是机器生成的。

研究人员生成并测量单个250秒极紫外线 (XUV) 脉冲,以记录原子电子动态. 这一突破允许实时观察原子内的电子运动,这对于理解原子过程至关重要.

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All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics
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All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics

Published on: January 19, 2018

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

相关实验视频

Last Updated: May 26, 2026

A Basic Positron Emission Tomography System Constructed to Locate a Radioactive Source in a Bi-dimensional Space
14:19

A Basic Positron Emission Tomography System Constructed to Locate a Radioactive Source in a Bi-dimensional Space

Published on: February 1, 2016

All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics
11:33

All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics

Published on: January 19, 2018

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

科学领域:

  • 原子物理 原子物理
  • 量子力学就是量子力学.
  • 超快速科学 超快速科学

背景情况:

  • 电子在原子中的轨道运动定义了原子动力学上的attosecond (as = 10^-18 s) 时间表.
  • 原子瞬态的实时记录需要在这个attosecond尺度上进行激发和探测.
  • 在生成低于femtosecond (fs = 10^-15 秒) 的极紫外 (XUV) 脉冲方面取得的进展使得探索attosecond模式成为可能.

研究的目的:

  • 为了证明单个250亚秒的XUV脉冲的生成和测量.
  • 为了利用这些脉冲来激发原子,并探测弹出的电子的动态.
  • 开发一种能够在波尔轨道时间内解决原子电子动态的瞬态记录器.

主要方法:

  • 生成和测量单个250秒的XUV脉冲.
  • 使用这些每秒的XUV脉冲激发原子.
  • 采用强烈的,波形控制的,短周期的激光脉冲来获得电子时势分布的断层图像.

主要成果:

  • 成功生成和测量单个250亚图秒的XUV脉冲.
  • 主光电子的断层成像提供了关于激发脉冲持续时间和频率扫描的准确信息.
  • 对二次奥格电子的断层成像为电子外放松动态提供了洞察力.

结论:

  • 开发的短暂记录器,使用~750nm激光探针和~100-eV激发,可以在attosecond时间尺度上解决原子电子动态.
  • 这种技术为研究原子中的超快电子动态开辟了新的途径.
  • 实时探测电子运动的能力提高了我们对基本原子过程的理解.