Field Ionization
Field Ionization - Related Videos
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.
03:12
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...
08:22
Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
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Cited by 5 •
2018
We present a protocol for probing ultrafast vibrational coherences in polyatomic radical cations that result in molecular dissociation.
07:31
Characterization of Recombination Effects in a Liquid Ionization Chamber Used for the Dosimetry of a Radiosurgical Accelerator
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Cited by 2 •
2014
A growing number of radiation therapy devices offer the advantage of delivering the dose through very small beams to the tumor, allowing for increased conformity and higher doses per fraction. Many different detectors can be used for the dosimetry of these small fields. In the present study, the effect of ion recombination is investigated for a liquid ionization chamber using a stereotactic radiation therapy system.
10:23
Electric Fields
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2023
Source: Yong P. Chen, PhD, Department of Physics & Astronomy, College of Science, Purdue University, West Lafayette, IN An electric field is generated by a charged object (referred to as the source charge) in the space around it, and represents the ability to exert electric force on another charged object (referred to as the test charge). Represented by a vector at any given point in the space, the electric field is the electrical force per unit test charge placed at that point (the force...
FAQs
The emitter's sharply pointed geometry concentrates the applied electric field at a very small region. This local intensification lowers the energy barrier that normally prevents electron removal from a gas-phase analyte. Because ion formation depends on this concentrated field, emitter shape is a central component of the process and helps initiate molecular-ion production under suitable conditions.
Field Ionization promotes electron removal through a strong electric field rather than through an energetic process that extensively breaks chemical bonds. As a result, the resulting molecular ion can remain relatively intact. This limited fragmentation helps analysts observe the ion corresponding to the original molecule instead of relying mainly on fragments to infer its mass.
Electron tunneling provides the immediate mechanism for overcoming the analyte's electron-removal barrier. The concentrated field near the emitter makes tunneling possible for the gas-phase atom or molecule, allowing an electron to escape and leaving a molecular ion. This mechanism explains why the technique can produce ionization without extensive molecular fragmentation.
In mass spectrometry, the method can preserve molecular ions that represent the analyte more directly than heavily fragmented spectra do. Detecting these ions supports accurate information about molecular mass and can reduce ambiguity when fragmentation would otherwise obscure the compound's structure. The approach is therefore useful when the intact molecular signal is analytically important.
Volatile organic compounds are especially relevant because the analyte must be available in the gas phase for the field-driven ionization process. The technique is also useful for compounds whose molecular structures could be obscured by extensive fragmentation. In these cases, retaining the molecular ion can make molecular-mass analysis more informative.
A chemist would favor Field Ionization when identifying or measuring an intact molecular ion is more important than obtaining extensive fragment information. Its soft ionization behavior can preserve molecular-mass information for volatile organic compounds and related analytes. This choice is particularly valuable when fragmentation from a higher-energy method would make the original molecular structure harder to interpret.