Resonance electron capture

Resonance electron capture directly yields the negative molecular ion, M"", whereas even-electron fragment ions are formed by dissociative electron capture and ion-pair formation. Molecular ions are generated by capture of electrons with 0-2 eV kinetic energy, whereas fragment ions are generated by capture of electrons from 0 to 15 eV. Ion-pair formation tends to occur when electron energies exceed 10 eV. [77]... 

Fig. 7.11. Energetics of (a) resonance electron capture, (b) dissociative electron capture, and (c) ion-pair formation. Adapted from Ref. [75] by permission. John Wiley Sons, 1981.

Wei, J. Liu, S. Fedoreyev, S.A. Vionov, V.G. A Study of Resonance Electron Capture Ionization on a Quadrupole Tandem Mass Spectrometer. Rapid Commrni. Mass Spectrom. 2000, 74,1689-1694. 

In Figure 1 are shown three negative ion APIMS spectra of perfluoromethylcy-clohexane (C7F,4) that were obtained under three different ion source conditions. It is well known that perfluorinated molecules of this size attach thermal electrons very rapidly to form molecular anions by the resonance electron capture (EC) mechanism (e + M M"), and this is what is observed in Figure la where pure nitrogen buffer gas has been used. In the use of certain analytical instruments for the detection of such compounds, however, protic molecules such as water or... 

In the case of sensitization of halouracil-containing DNA with ionizing radiation, attention has been drawn to potential contributions of resonant electron capture of low-energy electrons (Abdoul-Carine et al. 2001). The reaction of eaq with 8-Br-dGuo (Chap. 10.7) incorporated into DNA leads to a conversion of 8-Br-G into G in high yields with Z-form DNA being more effective than B-form DNA (Kimura et al. 2004). 

It is important to attempt to understand the mode of formation of the doubly-charged negative ions. Singly-charged negative ions are formed typically in a relatively low energy region by resonant electron capture... 

Polyselenophenes were analyzed by laser desorption/FT mass spectrometry <86MI 213-04.86MI213-06). Appearance potentials for the formation of negative ions in resonance electron capture of chalcogenophenes have been reported <91IZV590). 

This process, termed resonance electron capture (REC), occurs with high efficiency when electrons of near-thermal energies are available. These electrons are conveniently generated in the El source in the presence of a moderating gas such as H2, CH4, -C4Hio, NH3, N2, or Ar. With electrons of higher energies, the dissociative electron capture [reaction (2.15)] and ion-pair formation [reaction (2.16)] processes are also operative. 

Ionization methods that are based on the first approach are electron ionization resonance electron capture (REC), chemical ionization (CI), negative ion chemical ioniza-... 

Lim, H.K., Andrenyak, D., Francom, P. and Foltz, R.L. (1988) Quantification of LSD and N-demethyl-LSD in urine by gas chromatography/resonance electron capture ionization mass spectrometry. Anal. Chem., 60, 1420-1425. 

Lin, C. O Connor, P. B. Cournoyer, J. J. Use of a double resonance electron capture dissociation experiment to probe fragment intermediate lifetimes. J. Am. Soc. Mass Spectrom. 2006, 17, 1605-1615. 

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