Electron Ionization
Electron Ionization - Related Videos
03:12
Ionization Energy
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2020
The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy (IE1). The first ionization energy for an element, X, is the energy required to form a cation with 1+ charge: The energy required to remove the second most loosely bound electron is called the second ionization energy (IE2). The energy required to remove the third electron is the third ionization energy, and so on. Energy is always required...
06:58
Electrochemical Etching and Characterization of Sharp Field Emission Points for Electron Impact Ionization
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2016
A method for electrochemically etching field emission tips is presented. Etching parameters are characterized and the operation of the tips in field emission mode is investigated.
03:07
Electron Affinity
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2020
The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion). This process can be either endothermic or exothermic, depending on the element. Many of these elements have negative values of EA, which means that energy is released when the gaseous atom accepts an electron. However, for some elements, energy is required for the atom to become negatively charged, and the value of their EA is positive. Just as with ionization energy,...
02:48
Ionic Bonding and Electron Transfer
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2020
Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence shell, and an anion (a negative ion) forms when a neutral atom gains one or more electrons in its valence shell. Compounds composed of ions are called ionic compounds (or salts), and their constituent ions are held together by ionic bonds: electrostatic forces of attraction between oppositely charged cations and anions. Properties of Ionic...
06:21
Imaging of Biological Tissues by Desorption Electrospray Ionization Mass Spectrometry
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Cited by 21 •
2013
Desorption electrospray ionization mass spectrometry (DESI-MS) is an ambient method by which samples, including biological tissues, can be imaged with minimal sample preparation. By rastering the sample below the ionization probe, this spray-based technique provides sufficient spatial resolution to discern molecular features of interest within tissue sections.
FAQs
A 70 eV electron beam supplies enough energy to remove an electron from gas-phase molecules and often promotes reproducible fragmentation. This operating condition is important because the resulting ion patterns can be compared consistently between measurements. Standardized fragmentation improves the reliability of library-spectrum matching and supports identification across qualitative chemical analyses.
After electron removal, the resulting radical cation contains excess energy that can break apart into smaller charged fragments. These fragments are not random byproducts; their distribution can provide diagnostic information about molecular structure. Interpreting the fragment ions alongside the molecular ion signal helps researchers characterize compounds during mass spectrometric analysis.
Reproducibility allows an observed spectrum to be compared with reference spectra obtained under the same or standardized conditions. Matching characteristic ion patterns provides evidence for a compound’s identity, while the relative presence of diagnostic ions contributes structural information. This consistency is a major reason the technique supports routine qualitative analysis and compound-library searches.
The compound generally needs to be sufficiently volatile to enter the gas phase and thermally stable enough to pass through gas-chromatographic conditions without decomposing before ionization. When those requirements are met, gas chromatography separates the compounds before EI analysis, allowing their resulting ion patterns to be examined individually for identification or measurement.
The sample first reaches the gas phase in a vacuum, where it encounters a beam of energetic electrons. Electron removal produces charged molecular species, and excess energy may generate fragment ions. The mass spectrometer then detects these ions and records their pattern, which can be interpreted for compound identification, structural analysis, or chemical measurement.
EI is particularly useful for analyzing volatile and thermally stable compounds, especially when paired with gas chromatography. Its reproducible spectra support library-based identification, while the formation of diagnostic fragments assists structural analysis. The same measurements can contribute to qualitative work, such as determining what compounds are present, and quantitative chemical analysis, such as assessing their measured amounts.