Dissociative Excitation of Vacuum Ultraviolet Emission Features by Electron Impact on Molecular Gases. III. CO2

Mumma, M. J.; Stone, Edward J.; Borst, Walter L.; Zipf, E. C.

doi:10.1063/1.1678019

Cited by 47 publications

(32 citation statements)

References 17 publications

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“…3. Both spectra in this figure show weak C i multiplets whose relative intensities suggest electron impact dissociation of CO 2 (Ajello 1971b;Mumma et al 1972). However, electron impact dissociation of CO 2 has a considerably smaller cross section for the production of the CO bands than for C i λ1657 (Mumma et al 1971) and so the absence of CO emission in the left panel suggests that the observed emission in the right panel is due to solar resonance fluorescence.…”

Section: Discussionmentioning

confidence: 86%

“…We can exclude prompt photodissociation of H 2 O based on both the low photodissociation rate (Wu & Chen 1993) and the selection rules for H 2 O absorption (Wu & Judge 1988). Electron impact on CO 2 is the likely source of the weak C i λλ1561 and 1657 multiplets and the very weak C ii λ1335 multiplet (Ajello 1971a,b;Mumma et al 1972). The source of the electrons is photoionization of H 2 O and the resultant photoelectrons have peak energies in the range of 25 to 50 eV, although more energetic electrons have also been detected by the Ion and Electron Sensor (IES) instrument on Rosetta (Burch, priv.…”

Section: September Observationsmentioning

confidence: 99%

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Measurements of the near-nucleus coma of comet 67P/Churyumov-Gerasimenko with the Alice far-ultraviolet spectrograph on Rosetta

Feldman

A’Hearn

Bertaux

et al. 2015

A&A

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Aims. The Alice far-ultraviolet spectrograph onboard Rosetta is designed to observe emissions from various atomic and molecular species from within the coma of comet 67P/ Churyumov-Gerasimenko and to determine their spatial distribution and evolution with time and heliocentric distance. Methods. Following orbit insertion in August 2014, Alice made observations of the inner coma above the limbs of the nucleus of the comet from cometocentric distances varying between 10 and 80 km. Depending on the position and orientation of the slit relative to the nucleus, emissions of atomic hydrogen and oxygen were initially detected. These emissions are spatially localized close to the nucleus and spatially variable with a strong enhancement above the comet's neck at northern latitudes. Weaker emission from atomic carbon and CO were subsequently detected. Results. Analysis of the relative line intensities suggests photoelectron impact dissociation of H 2 O vapor as the source of the observed H i and O i emissions. The electrons are produced by photoionization of H 2 O. The observed C i emissions are also attributed to electron impact dissociation, of CO 2 , and their relative brightness to H i reflects the variation of CO 2 to H 2 O column abundance in the coma.

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Section: Discussionmentioning

confidence: 86%

Section: September Observationsmentioning

confidence: 99%

Measurements of the near-nucleus coma of comet 67P/Churyumov-Gerasimenko with the Alice far-ultraviolet spectrograph on Rosetta

Feldman

A’Hearn

Bertaux

et al. 2015

A&A

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show abstract

“…2. The electron impact excitation functions fall off relatively slowly at high energies; this indicates that the initial excitation in this energy region is a dipole-allowed transition [Mumma et al, 1971a]. However, the excitation functions for CO(A, v' = 0, 1) (and possibly v' = 4) exhibit sharp early peaks near 30 eV.…”

Section: Their Instrumental Wavelength Resolution (• 10/•) Was Too Lowmentioning

confidence: 96%

Nonthermal rotational distribution of CO(A¹Π) fragments produced by dissociative excitation of CO₂by electron impact

Mumma¹,

Stone²,

Zipf³

1975

J. Geophys. Res.

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Bands of the CO(A¹Π‐X¹Σ+) fourth‐positive group (4PG) were excited by electron impact dissociative excitation of CO2, and their rotational profiles were measured. The corresponding rotational distributions were found to be nonthermal but rotationally ‘hot’ with respect to a 300°K distribution. Bands originating from υ′ = 0 and 1 have similar rotational distributions, which are ‘hotter’ than the distribution for υ′ = 2. The rotational profiles were measured at selected electron impact energies in the range from 20 to 300 eV. The rotational distributions for all three levels become broader with increasing electron energy and ‘saturate’ at about 40 eV. This may mean that dissociation through bent states becomes relatively more important as the dipole‐allowed limit is reached, whereas linear states are relatively more important at very low electron energies. The low‐energy profiles for υ′ = 0 and 1 are reproduced by a model that assumes that the CO fragment carries away all of the rotational angular momentum of the CO2 parent, but this model fails for υ′ = 2. The results are discussed in terms of their applicability to the Mariner observations of the CO 4PG in the dayglow of Mars.

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“…The measured energy dependence of the aA/an ratio is the same in both experiments[Zipf, 1985a, b]. for this process has been used as a calibration standard by Mumrna andZipf [1971] and byStone and Zipf [1974] Shemansky et al [1985],. Van Zyl et al…”

mentioning

confidence: 99%

Electron impact excitation of atomic oxygen: Revised cross sections

Zipf¹,

Erdman²

1985

J. Geophys. Res.

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100

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Revised cross‐section values for the excitation of the O I(3s ³S°‐2p ³P; λ1304 Å), O I(3d ³D°‐2p ³P; λ1027 Å), and O I(3s′ ³D°‐2p ³P; λ989 Å) resonance transitions by electron impact on atomic oxygen are presented from threshold to 300 eV. These results are smaller than the excitation cross sections used in some airglow models by a factor of ∼2.8. The revised values are in good agreement with recent quantum‐scattering calculations. The downward revision is required by new laboratory studies in which the direct and dissociative cross sections for λ1304 Å excitation were normalized with small probable error to the O and O2 ionization cross sections. The results also reflect new advances in VUV optical calibration techniques. A number of outstanding airglow problems are simplified by these revisions.

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Dissociative Excitation of Vacuum Ultraviolet Emission Features by Electron Impact on Molecular Gases. III. CO2

Cited by 47 publications

References 17 publications

Measurements of the near-nucleus coma of comet 67P/Churyumov-Gerasimenko with the Alice far-ultraviolet spectrograph on Rosetta

Measurements of the near-nucleus coma of comet 67P/Churyumov-Gerasimenko with the Alice far-ultraviolet spectrograph on Rosetta

Nonthermal rotational distribution of CO(A¹Π) fragments produced by dissociative excitation of CO₂by electron impact

Electron impact excitation of atomic oxygen: Revised cross sections

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Dissociative Excitation of Vacuum Ultraviolet Emission Features by Electron Impact on Molecular Gases. III. CO2

Cited by 47 publications

References 17 publications

Measurements of the near-nucleus coma of comet 67P/Churyumov-Gerasimenko with the Alice far-ultraviolet spectrograph on Rosetta

Measurements of the near-nucleus coma of comet 67P/Churyumov-Gerasimenko with the Alice far-ultraviolet spectrograph on Rosetta

Nonthermal rotational distribution of CO(A¹Π) fragments produced by dissociative excitation of CO2by electron impact

Electron impact excitation of atomic oxygen: Revised cross sections

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Resources

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Nonthermal rotational distribution of CO(A¹Π) fragments produced by dissociative excitation of CO₂by electron impact