Related Experiment Video
Updated: Aug 3, 2026
09:40
Measurement and Analysis of Atomic Hydrogen and Diatomic Molecular AlO, C2, CN, and TiO Spectra Following Laser-induced Optical Breakdown
Published on: February 14, 2014
Delayed ionization and fragmentation en route to thermionic emission: statistics and dynamics
1School of Physics and Engineering Physics, Göteborg University, Göteborg, SE-41296 Sweden. eleanor.campbell@fy.chalmers.se
Annual Review of Physical Chemistry
|October 14, 2000
Summary
Thermionic emission, a slow decay process, involves energy-rich molecules and clusters releasing electrons over microseconds. Future research should explore experimental signatures and theoretical aspects of this delayed ionization.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Materials Science
Background:
- Thermionic emission is a decay mechanism for excited molecules and clusters.
- This process can occur over extended timescales (microseconds).
- It is relevant for large molecules, metallic clusters, and fullerenes.
Purpose of the Study:
- To review the current understanding of thermionic emission as a long-time decay mode.
- To identify knowledge gaps and necessary future research directions.
- To highlight experimental and theoretical challenges.
Main Methods:
- Review of existing experimental data and theoretical studies.
- Discussion of potential experimental signatures.
- Analysis of theoretical indications of delayed ionization.
Main Results:
- Thermionic emission can be a slow (microseconds) decay process.
- Delayed ionization may not follow purely statistical behavior.
- Electron emission competes with fragmentation and radiative cooling.
Conclusions:
- Coupling between electronic and nuclear modes can delay ionization.
- Long time-delayed ionization is observable, preceding full energy partitioning.
- Further experimental and theoretical work is crucial for a complete understanding.
Related Concept Videos
01:21Chemical Ionization (CI) Mass Spectrometry
The molecular ion peak of a molecule in the mass spectrum provides vital information for molecular identification. However, conventional electron impact ionization can lead to the rapid dissociation of some molecular ions before they reach the detector. A milder ionization method is required to increase the lifetime of such ionized analyte molecules. Chemical ionization (CI) is a gas-phase protonation reaction useful for mass-analyzing analyte molecules that are easily protonated to yield the...
01:19Thomson'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...
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...
01:27Atomic Spectroscopy: Effects of Temperature
Atomization, converting samples into gas-phase atoms and ions, is essential for atomic spectroscopy. The flame temperature required for atomization affects the efficiency of the atomic spectroscopic methods by increasing the atomization efficiency and the relative population of the excited and ground states.
At thermal equilibrium, the relative populations of excited and ground state atoms can be estimated using the Maxwell–Boltzmann distribution. For example, an increase in temperature from...
At thermal equilibrium, the relative populations of excited and ground state atoms can be estimated using the Maxwell–Boltzmann distribution. For example, an increase in temperature from...
01:20Atomic Emission Spectroscopy: Overview
Atomic emission spectroscopy (AES) is an analytical technique used to determine the elemental composition of a sample by analyzing the light emitted from excited atoms. In AES, atoms in a sample are excited to higher energy levels by thermal energy from high-temperature sources, such as plasma, arcs, or sparks. When these excited atoms return to lower energy states, they emit light at specific wavelengths characteristic of each element. The resulting atomic emission spectrum, which consists of...
01:22Atomic 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.
01:29Atomic Emission Spectroscopy: Lab
AES is a powerful analytical technique, especially effective when used with plasma sources, producing abundant spectra in characteristic emission lines. The Inductively Coupled Plasma (ICP), in particular, yields superior quantitative analytical data due to its high stability, low noise, low background, and minimal interferences under optimal experimental conditions. However, newer air-operated microwave sources are emerging as promising alternatives that could be more cost-effective than...