The energies of the triply excited n = 2 intrashell He− resonances 2s22p and 2s2p2 revisited

Fiegele, T.; Mason, Nigel J.; Foltin, V.; Stamatovic, A.; Scheier, P.; Märk, T.D.

doi:10.1016/s1387-3806(01)00436-5

Cited by 11 publications

(10 citation statements)

References 24 publications

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“…We also note that systematically lower values were obtained in comparison to the previous EI values by Klebe et al [26]. This deviation may be explained by the increased precision of the electron energy scale due to the utilization of an electron monochromator [53] in our study. 2NI exhibits similar fragment cations to IMI, such as, m / z 67 C 3 H 3 N 2 + , 40 HNCCH + , and 28 HCNH + .…”

Section: Discussioncontrasting

confidence: 72%

Electron Ionization of Imidazole and Its Derivative 2-Nitroimidazole

Meißner

Feketeová

Ribar

et al. 2019

J. Am. Soc. Mass Spectrom.

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Imidazole (IMI) is a basic building block of many biologically important compounds. Thus, its electron ionization properties are of major interest and essential for the comparison with other molecular targets containing its elemental structure. 2-Nitroimidazole (2NI) contains the imidazole ring together with nitrogen dioxide bound to the C2 position, making it a radiosensitizing compound in hypoxic tumors. In the present study, we investigated electron ionization of IMI and 2NI and determined the mass spectra, the ionization energies, and appearance energies of the most abundant fragment cations. The experiments were complemented by quantum chemical calculations on the thermodynamic thresholds and potential energy surfaces, with particular attention to the calculated transition states for the most important dissociation reactions. In the case of IMI, substantially lower threshold values (up to ~ 1.5 eV) were obtained in the present work compared to the only available previous electron ionization study. Closer agreement was found with recent photon ionization values, albeit the general trend of slightly higher values for the case of electron ionization. The only exception for imidazole was found in the molecular cation at m/z 40 which is tentatively assigned to the quasi-linear HCCNH+/ HCNCH+. Electron ionization of 2NI leads to analogous fragment cations as in imidazole, yet different dissociation pathways must be operative due to the presence of the NO2 group. Regarding the potential radiosensitization properties of 2NI, electron ionization is characterized by dominant parent cation formation and release of the neutral NO radical. Electronic supplementary materialThe online version of this article (10.1007/s13361-019-02337-w) contains supplementary material, which is available to authorized users.

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Section: Discussioncontrasting

confidence: 72%

Electron Ionization of Imidazole and Its Derivative 2-Nitroimidazole

Meißner

Feketeová

Ribar

et al. 2019

J. Am. Soc. Mass Spectrom.

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“…In a double excitation resonance, the ionization cross section exhibits an interference between the direct ionization and autoionization pathways [203]. Fano resonances were also reported by Fiegele et al upon electron impact of gas phase He [181] and thus doubly-excited states are expected to also contribute to the ionization processes upon electron bombardment of pure and doped HNDs.…”

Section: Photoionization Of Undoped Helium Nanodropletsmentioning

confidence: 53%

“…The quadratic dependence of the ion signal of He + formed at 22 eV on the electron current supports the proposed model. It is interesting to note that the ion efficiency curve of He + measured via electron ionization of gas phase He exhibits narrow Fano resonances that can be assigned to doubly-excited states [181] that form with the projectile electron short lived transient negative anions. The lifetimes of these autoionizing states may be strongly affected by the surrounding He atoms.…”

Section: Threshold Energies Of Small Hen + Ionsmentioning

confidence: 99%

Cold physics and chemistry: Collisions, ionization and reactions inside helium nanodroplets close to zero K

et al. 2018

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“…(See also Grissom et al, 1969). Many succeeding studies have been devoted to the characterization of the position and shape of these resonances with general agreement (a recent article summarizes these results (Fiegele et al, 2001)).…”

Section: Experimetal Methodsmentioning

confidence: 84%

Electron ionization time‐of‐flight mass spectrometry: Historical review and current applications

Mirsaleh-Kohan

Robertson

Compton

2008

Mass Spectrometry Reviews

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This review presents an overview of electron ionization time-of-flight mass spectroscopy (EITOFMS), beginning with its early development to the employment of modern high-resolution electron ionization sources. The EITOFMS is demonstrated to be ideally suited for analytical and basic chemical physics studies. Studies of the formation of positive ions by electron ionization time-of-flight mass spectroscopy have been responsible for many of the known ionization potentials of molecules and radicals, as well as accepted bond dissociation energies for ions and neutral molecules. The application of TOFMS has been particularly important in the area of negative ion physics and chemistry. A wide variety of negative ion properties have been discovered and studied by using these methods including: autodetachment lifetimes, metastable dissociation, Rydberg electron transfer reactions and field detachment, SF(6) Scavenger method for detecting temporary negative ion states, and many others.

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The energies of the triply excited n = 2 intrashell He− resonances 2s22p and 2s2p2 revisited

Cited by 11 publications

References 24 publications

Electron Ionization of Imidazole and Its Derivative 2-Nitroimidazole

Electron Ionization of Imidazole and Its Derivative 2-Nitroimidazole

Cold physics and chemistry: Collisions, ionization and reactions inside helium nanodroplets close to zero K

Electron ionization time‐of‐flight mass spectrometry: Historical review and current applications

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