Metastable fragment production following electron impact on CO<sub>2</sub>

Allcock, G.R.; McConkey, J W

doi:10.1088/0022-3700/9/12/025

Cited by 29 publications

(16 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Results for O* (HR) species have been reported [12,13,30]. At low electron impact energy, the dissociative excitation results correlate well with the present dissociative ionization data.…”

Section: The O + Dissociation Channelsupporting

confidence: 88%

See 1 more Smart Citation

The dissociative electroionization of carbon dioxide by low-energy electron impact. The C+, O+ and CO+ dissociation channels

Locht

Davister

1995

International Journal of Mass Spectrometry and Ion Processes

View full text Add to dashboard Cite

This work reports the dissociative ionization of CO 2 between 19 and 40 eV. The three dissociation channels producing C + , O + and CO + are examined in detail. Translational energy distributions as a function of the impinging electron energy and the ionization efficiency for fixed minimum kinetic energy carried by the fragments are measured. The kinetic energy versus appearance energy diagram is obtained for the three fragment ions. When available, the present results are compared with previous measurements. The lowest appearance energy of O + and CO + corresponds to the predissocia-tion of the CO 2 + (C 2 Σ g + ) state. At higher energies, all the fragment ions are exclusively produced by the dissociative ionization of CO 2 in the multiple electron transition (MET) states. Predissociation is most probably the dominant mechanism. Each MET state branches off to produce not only the three fragments, but also the same fragment in two different states. This is observed for each dissociation channel, i.e. O + , CO + and/or C + . In the latter channel no evidence is found for the dissociative ionization reaction CO 2 + → C + + 2O.

show abstract

“…Results for O* (HR) species have been reported [12,13,30]. At low electron impact energy, the dissociative excitation results correlate well with the present dissociative ionization data.…”

Section: The O + Dissociation Channelsupporting

confidence: 88%

“…Allcock and McConkey [30] measured the excitation threshold at 19.2 ± 1.0 eV and obtained a KE versus AE straight line with a slope of 28/44 = 0.63. Misakian et al [13] only measured the onset of O* at 20.5 eV.…”

Section: Discussionmentioning

confidence: 99%

The dissociative electroionization of carbon dioxide by low-energy electron impact. The C+, O+ and CO+ dissociation channels

Locht

Davister

1995

International Journal of Mass Spectrometry and Ion Processes

View full text Add to dashboard Cite

show abstract

“…Various theoretical models have appeared in the literature, and many types of experiments have been performed, in order to determine the energy dependence of the magnitude of the cross sections involved in the elastic, inelastic, ionizing, and dissociative processes resulting from the collision of an electron with a molecule. − These phenomena are induced by the potential interaction between the electron and the target molecule. − It has been found desirable for understanding the essential physics of the scattering phenomenon to divide the process into resonant and direct. , When the time-dependent amplitude of the projectile electron wave function does not increase significantly in the vicinity of a small molecule , or a molecular site of a large molecule, the scattering process is considered to be direct; otherwise, it is resonant. With dependence on electron energy, elastic and inelastic scattering can proceed by both mechanisms. ,− Dissociative electronically excited states can break bonds, − but below the energy threshold for electronic excitation, only dissociative electron attachment (DEA) can dissociate molecules. , Since at resonance energies, the electron interacts more strongly with the target and for a longer time, bond dissociation can be considerably increased by TMAs that cause maxima in the yield functions of molecular damages . In a large molecule, such as oligonucleotides and DNA, both direct and resonance scattering processes occur and can lead to bond cleavage. , Nonresonant cross sections, generally, show a smooth, slowly varying, energy dependence. − This nonresonant behavior can be seen in the yield functions of neutral radicals. − In the case of short DNA strands, the LEE yield functions of neutral species provide good examples of resonance maxima superimposed on a smoothly varying background caused by direct scattering. , …”

Section: Discussionmentioning

confidence: 99%

Role of Transient Anions in Chemoradiation Therapy: Base Modifications, Cross-Links, and Cluster Damages Induced to Cisplatin-DNA Complexes by 1–20 eV Electrons

et al. 2020

View full text Add to dashboard Cite

The molecular mechanism of platinum-based drugs in concomitant chemoradiation therapy relies on enhancement of DNA damage in cancer cells, particularly that of detrimental clustered lesions and cross-links induced by the abundant low-energy electrons (LEEs) generated by ionizing radiation. We provide the complete 1−20 eV electron-energy dependence of the yields of all conformational LEE-induced lesions to biological DNA, when it binds to five molecules of the chemotherapeutic drug cisplatin. Recording at 1 eV intervals clearly show that the enhancement of all lesions is particularly intense at the energies of coreexcited transient molecular anions (i.e., TMAs at 5, 6, and 10 eV). New TMAs are observed at 14 and 18 eV, only in yield functions of cisplatin-DNA complexes. Enhancements of all lesions by cisplatin are quantified over the 1−20 eV range, where maxima appear at 14 and 18 eV. The most detrimental lesions to cell survival exhibit the highest enhancements by factors of 2−3. Whereas no cluster lesions are induced by electrons of energy <5 eV in DNA, LEEs of any energy cause clustered damages in the complex. These results confirm the current notion that LEEs and TMAs play a dominant role in the molecular mechanism of platinum-drug chemoradiation therapy.

show abstract

“…We compare the model glow profiles for three different kinetic energy values: 0.1, 1, and 10 eV, since the lifetime of O(3 s 5 S o ) is now well established at 180 μs. The TOF studies of electron impact dissociative excitation of CO 2 by numerous groups (e.g., Allcock & McConkey, ; Barnett et al, ; Misakian et al, ) have been reviewed by McConkey et al (). TOF measurements have revealed, in addition to high‐Rydberg O‐fragments, the presence of mainly two electronically excited fragments: slow CO ( a 3 Π) molecules and relatively fast O ( 5 S o ) atoms.…”

Section: Kinetic Energy Of O (5so) Atoms From Electron Impact Dissocimentioning

confidence: 99%

UV Study of the Fourth Positive Band System of CO and O i 135.6 nm From Electron Impact on CO and CO₂

et al. 2019

View full text Add to dashboard Cite

We have measured the 30 and 100 eV far ultraviolet (FUV) emission cross sections of the optically allowed Fourth Positive Group (4PG) band system (A 1 Π → X 1 Σ + ) of CO and the optically forbidden O ( 5 S o → 3 P) 135.6 nm atomic transition by electron-impact-induced-fluorescence of CO and CO 2 . We present a model excitation cross section from threshold to high energy for the A 1 Π state, including cascade by electron impact on CO. The A 1 Π state is perturbed by triplet states leading to an extended FUV glow from electron excitation of CO. We derive a model FUV spectrum of the 4PG band system from dissociative excitation of CO 2 , an important process observed on Mars and Venus. Our unique experimental setup consists of a large vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission Imaging Ultraviolet Spectrograph optical engineering unit, operating in the FUV (110-170 nm). The determination of the total O I ( 5 S o ) at 135.6 nm emission cross section is accomplished by measuring the cylindrical glow pattern of the metastable emission from electron impact by imaging the glow intensity about the electron beam from nominally zero to~400 mm distance from the electron beam. The study of the glow pattern of O I (135.6 nm) from dissociative excitation of CO and CO 2 indicates that the O I ( 5 S o ) state has a kinetic energy of~1 eV by modeling the radial glow pattern with the published lifetime of 180 μs for the O I ( 5 S o ) state.Plain Language Summary Both Mars and Venus have upper atmospheres that are similar in composition: mostly CO 2 , CO, and N 2 are dominant molecular gases, with nearly identical UV spectra. The modeling studies of atmospheric UV emissions cannot presently be accurately conducted to the same accuracy as the planetary UV measurements, which avail themselves with state-of-the-art calibrated spectrographs. This dichotomy in accuracy between planetary observation and model occurs because the atomic and molecular emission cross sections with uncertainties of certain transitions are greater than 100%. Furthermore, the analysis is complicated by the spectral blending of the various emissions of the low-resolution spectral spaceborne instruments. We present in this paper a UV laboratory instrument unique in the world at the University of Colorado that can measure for the first time the excitation mechanisms with accurate emission cross sections of both allowed and optically forbidden transitions that are occurring in a planetary atmosphere. Key Points: • We measured 30 and 100 eV emission cross sections of Fourth Positive band system of CO and O I (135.6 nm) from electron impact on CO and CO 2 • We conducted a laboratory experiment measuring single-scattering electron-impactinduced-fluorescence FUV spectra from excitation of CO and CO 2 • Fragment kinetic energy measurement for O I ( 5 S o ) atoms found to be around~1 eV from both CO and CO 2 molecular dissociation Correspondence to: et al. (2019). UV study of the Fourth Positive band system ...

show abstract

Metastable fragment production following electron impact on CO₂

Cited by 29 publications

References 13 publications

The dissociative electroionization of carbon dioxide by low-energy electron impact. The C+, O+ and CO+ dissociation channels

The dissociative electroionization of carbon dioxide by low-energy electron impact. The C+, O+ and CO+ dissociation channels

Role of Transient Anions in Chemoradiation Therapy: Base Modifications, Cross-Links, and Cluster Damages Induced to Cisplatin-DNA Complexes by 1–20 eV Electrons

UV Study of the Fourth Positive Band System of CO and O i 135.6 nm From Electron Impact on CO and CO₂

Contact Info

Product

Resources

About

Metastable fragment production following electron impact on CO2

Cited by 29 publications

References 13 publications

The dissociative electroionization of carbon dioxide by low-energy electron impact. The C+, O+ and CO+ dissociation channels

The dissociative electroionization of carbon dioxide by low-energy electron impact. The C+, O+ and CO+ dissociation channels

Role of Transient Anions in Chemoradiation Therapy: Base Modifications, Cross-Links, and Cluster Damages Induced to Cisplatin-DNA Complexes by 1–20 eV Electrons

UV Study of the Fourth Positive Band System of CO and O i 135.6 nm From Electron Impact on CO and CO2

Contact Info

Product

Resources

About

Metastable fragment production following electron impact on CO₂

UV Study of the Fourth Positive Band System of CO and O i 135.6 nm From Electron Impact on CO and CO₂