Radical singly-charged

El predominantly creates singly charged ions from the precursor neutral. If the neutral was a molecule as in most cases, it started as having an even number of electrons, i.e., it was an even-electron (closed-shelT) molecule. The molecular ion formed must then be a radical cation or an odd-electron open-shell) ion as these species are termed, e.g., for methane we obtain ... 

Note As one electron charge is neutralized upon EC, the precursor ion for ECD must at least be a doubly charged positive even-electron ion to yield a singly charged radical ion for subsequent dissociation. 

Electron ionization mainly creates singly charged positive ions by ejection of one electron out of the neutral. If the precursor was a molecule, M, it will have an even number of electrons, i.e., an even-electron or closed-shell species. The molecular ion formed upon EI must then be a positive radical ion, M" , odd-electron or open-shell) ion. 

Definition The molecular ion has the same empirical formula as the corresponding neutral molecule. The neutral and its molecular ion only differ by one (or more) electron(s). A singly charged molecular ion can either be a positive radical ion, M" , or a negative radical ion, M" (not in case of El). The mass of this ion corresponds to the sum of the masses of the most abundant isotopes of the various atoms that make up the molecule (with a correction for the elec-tron(s) lost or gained. Chap. 3.1.4). [8,9]... 

Using conventional electron ionization mass spectrometry, everything occurs in a vacuum such that any collision is highly unlikely. The molecule receives energy from an electron beam and is ionized into a radical cation. The ion that is thus formed is subjected to an electric field that directs it towards the analyser. For instance, suppose a singly charged 100 u mass ion is accelerated by a 1000 V potential difference in the source. This ion has a mass of... 

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