Titan airglow spectra from the Cassini Ultraviolet Imaging Spectrograph: FUV disk analysis

Ajello, J. M.; Gustin, Jacques; Stewart, Ian; Larsen, K. W.; Esposito, L. W.; Pryor, W. R.; McClintock, W. E.; Stevens, M. H.; Malone, C. P.; Dziczek, D.

doi:10.1029/2007gl032315

Cited by 64 publications

(49 citation statements)

References 26 publications

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“…Further electron-induced fluorescence occurs from the Lyman-Birge-Hopfield (LBH) series of bands originating from the a 1 Π g excited state. The UV emission studies of N 2 by electron-impact-induced fluorescence carried out over the past 30 years at the Jet Propulsion Laboratory (JPL) have been motivated by both astrophysical and theoretical interest (Ajello & Shemansky 1985;Ajello et al 1989Ajello et al , 1998Ajello et al , 2007Ajello et al , 2008Ajello et al , 2011aAjello et al , 2011bAjello et al , 2012James et al 1990;Mangina et al 2011;Young et al 2010). Intense atomic emissions in the dayglow from the atmospheres of N 2 -bearing solar system objects occur mainly from solar photodissociative ionization (PDI) and in the nightglow by collision with secondary electrons and other particles (e.g., magnetospheric protons and O + ; Ajello et al 2011aAjello et al , 2011bAjello et al , 2012Cravens et al 2008Cravens et al , 2010.…”

Section: Introductionmentioning

confidence: 99%

“…The Cassini spacecraft orbiting the Saturn system is equipped with a low-resolution (λ/Δλ = 200) Ultraviolet Imaging Spectrograph (UVIS) operated in two spectral channels spanning the range from 561 to 1913 Å, and the UV-visible-near-IR Imaging Sub-System (Esposito et al 2004). The former instrument is capable of observing N 2 in the Titan airglow in the EUV and FUV, and the latter is suitable to study N 2 eclipse darkside emissions filtered into 15 band passes covering the UV-visiblenear-IR spectral range (2350-11000 Å; Ajello et al 2007Ajello et al , 2008Stevens et al 2011;Mangina et al 2011;West et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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THE HIGH-RESOLUTION EXTREME-ULTRAVIOLET SPECTRUM OF N ₂ BY ELECTRON IMPACT

Heays

Ajello

Aguilar

et al. 2014

ApJS

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We have analyzed high-resolution (FWHM = 0.2 Å) extreme-ultraviolet (EUV, 800-1350 Å) laboratory emission spectra of molecular nitrogen excited by an electron impact at 20 and 100 eV under (mostly) optically thin, singlescattering experimental conditions. A total of 491 emission features were observed from N 2 electronic-vibrational transitions and atomic N i and N ii multiplets and their emission cross sections were measured. Molecular emission was observed at vibrationally excited ground-state levels as high as v = 17, from the a 1 Π g , b 1 Π u , and b 1 Σ u + excited valence states and the Rydberg series c n+1 1 Σ u + , c n 1 Π u , and o n 1 Π u for n between 3 and 9. The frequently blended molecular emission bands were disentangled with the aid of a sophisticated and predictive quantummechanical model of excited states that includes the strong coupling between valence and Rydberg electronic states and the effects of predissociation. Improved model parameters describing electronic transition moments were obtained from the experiment and allowed for a reliable prediction of the vibrationally summed electronic emission cross section, including an extrapolation to unobserved emission bands and those that are optically thick in the experimental spectra. Vibrationally dependent electronic excitation functions were inferred from a comparison of emission features following 20 and 100 eV electron-impact collisional excitation. The electron-impact-induced fluorescence measurements are compared with Cassini Ultraviolet Imaging Spectrograph observations of emissions from Titan's upper atmosphere.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

THE HIGH-RESOLUTION EXTREME-ULTRAVIOLET SPECTRUM OF N ₂ BY ELECTRON IMPACT

Heays

Ajello

Aguilar

et al. 2014

ApJS

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“…In contrast to photo-excitation, electron impact implies also optically forbidden excited states and monitors their subsequent decay to lower states. Pang et al investigated electron impact emission cross sections for CH 4 and C 2 H 2 in the VUV region from 40 to 200 nm [17]. Three studies are most related to the present study since electrons were used as projectiles and fluorescence signals in the VIS/UV range were recorded.…”

Section: Introductionmentioning

confidence: 99%

“…This arises from the fact that methane is present in planetary atmospheres (like, for example, Earth, Jupiter or Titan) [2][3][4][5][6][7] as well as in the interstellar medium [8]. Moreover, it is also of relevance in the divertor region of thermonuclear fusion plasmas [9] and in technological low temperature plasmas [10].…”

Section: Introductionmentioning

confidence: 99%

Electron impact excitation of methane: determination of appearance energies for dissociation products

Danko

Országh

Ďurian

et al. 2013

J. Phys. B: At. Mol. Opt. Phys.

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In this work, we present an experimental study of dissociative excitation of CH 4 utilizing a crossed electron molecular beam experiment. Methane was excited by nearly monochromatic electrons generated by a trochoidal electron monochromator. The dissociative products were identified on the basis of the emission spectra in the ultraviolet-visible (UV/VIS) spectral range. The excitation functions were recorded as the function of the electron energy for different emission bands of the fragments (Balmer series for H: n = 3,4 . . . 9→2, and moreover, CH: A 2 →X 2 , CH: B S 0 ). From the experimental data we have determined the threshold energies for excitation of particular fragments. Present experimental results indicate that the threshold energies for some dissociative excitation channels could be lower by ∼1-2 eV in comparison to earlier studies and indicate that different dissociative processes may be operative at the threshold than assumed in the former studies.

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“…The LymanBirge-Hopfield (LBH) band is one of the most important molecular emissions of excited nitrogen in the FUV. It is always found and can be produced due to impact excitation of protons and electrons in the aurora and airglow observations of nitrogen-bearing atmospheres of Earth [e.g., Bishop and Feldman, 2003;Strickland et al, 2001], Titan [e.g., Ajello et al, 2008;Sittler et al, 2009] and Triton [e.g., Broadfoot et al, 1989] and is expected at Pluto [Stern et al, 2008].…”

Section: Introductionmentioning

confidence: 99%

Laboratory studies of UV emissions from proton impact on N₂: The Lyman-Birge-Hopfield band system for aurora analysis

et al. 2011

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[1] We have measured the emission cross sections of the Lyman-Birge-Hopfield (LBH) a 1 P g − X 1 S g + band system and several atomic nitrogen (N I) multiplets (1200, 1243, 1493 Å) by H + (proton) impact on N 2 over an impact energy range of 1-7 keV. The peak proton-impact-induced emission cross section of the LBH band system (1260-2500 Å) was measured to be 5.05 ± 1.52 × 10 −17 cm 2 at 7 keV. To the best of our knowledge, the present LBH emission cross sections are reported for the first time in the far ultraviolet (FUV) wavelength range of 1100-1600 Å. The proton energy range in this study, when coupled with previously published 10-100 keV proton excited emissions of N I multiplets, provides a wide energy range of emission cross sections for proton energy loss transport codes. This energy range includes the peak cross section and the energy range for Born scaling. The reported measurements lead to an important component of monoenergetic yields for proton FUV auroral emission. Such yields, based on emission cross sections and transport modeling, allowed for convenient comparison of emission efficiencies between proton and electron aurora. In addition, we have measured the H Ly a, LBH, and N I multiplet emission cross sections for H 2 + and H 3 + ion impact on N 2 at 5 keV and found that the magnitude of H Ly a emission cross section, s em (Ly a), follows in the order of impact ion mass H 3 + > H 2 + > H + .Citation: Ajello, J. M., R. S. Mangina, D. J. Strickland, and D. Dziczek (2011), Laboratory studies of UV emissions from proton impact on N 2 : The Lyman-Birge-Hopfield band system for aurora analysis,

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Titan airglow spectra from the Cassini Ultraviolet Imaging Spectrograph: FUV disk analysis

Cited by 64 publications

References 26 publications

THE HIGH-RESOLUTION EXTREME-ULTRAVIOLET SPECTRUM OF N ₂ BY ELECTRON IMPACT

THE HIGH-RESOLUTION EXTREME-ULTRAVIOLET SPECTRUM OF N ₂ BY ELECTRON IMPACT

Electron impact excitation of methane: determination of appearance energies for dissociation products

Laboratory studies of UV emissions from proton impact on N₂: The Lyman-Birge-Hopfield band system for aurora analysis

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Titan airglow spectra from the Cassini Ultraviolet Imaging Spectrograph: FUV disk analysis

Cited by 64 publications

References 26 publications

THE HIGH-RESOLUTION EXTREME-ULTRAVIOLET SPECTRUM OF N 2 BY ELECTRON IMPACT

THE HIGH-RESOLUTION EXTREME-ULTRAVIOLET SPECTRUM OF N 2 BY ELECTRON IMPACT

Electron impact excitation of methane: determination of appearance energies for dissociation products

Laboratory studies of UV emissions from proton impact on N2: The Lyman-Birge-Hopfield band system for aurora analysis

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THE HIGH-RESOLUTION EXTREME-ULTRAVIOLET SPECTRUM OF N ₂ BY ELECTRON IMPACT

THE HIGH-RESOLUTION EXTREME-ULTRAVIOLET SPECTRUM OF N ₂ BY ELECTRON IMPACT

Laboratory studies of UV emissions from proton impact on N₂: The Lyman-Birge-Hopfield band system for aurora analysis