UV Molecular Spectroscopy from Electron Impact for Applications to Planetary Atmospheres and Astrophysics

Ajello, J. M.; Mangina, Rao S.; Meier, R. R.

doi:10.1201/b10389-29

Cited by 16 publications

(33 citation statements)

References 136 publications

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“…The excitation of the N 2 Rydberg-valence states responsible for these emissions occurs in the short wavelength portion of the EUV between 800 and 1000 Å. This excitation, emission, and associated dissociation and ionization play a role in establishing the physical composition of the N 2 -bearing atmospheres of Earth (Meier et al 2005;Meier & Picone 1994;Knight et al 2008;Strickland et al 1999Strickland et al , 2004aStrickland et al , 2004b, Titan (Ajello et al 2007(Ajello et al , 2011bStevens et al 1994Stevens et al , 2011Stevens 2001;Broadfoot et al 1981;Fulchignoni et al 2005), Triton (Broadfoot et al 1989;Summers & Strobel 1991), and Pluto (Zhu et al 2014;Stern et al 2008;Bagenal et al 1997), and in interstellar clouds and extrasolar protoplanetary disks (Maret et al 2006;Pascucci et al 2009;Li et al 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The important electronic transitions proceed from the X 1 Σ g + ground state to a manifold of closely spaced (12-15 eV) states (Ajello et al 2011b), which are then the sources of EUV emissions observed by spacecraft (Ajello et al 2007(Ajello et al , 2011aStevens et al 2011). Two of these states, b 1 Π u and b 1 Σ u + , are of the valence type and the remainder fall into three Rydberg series, with lowest members c 4 1 Σ u + , c 3 1 Π u , and o 3 1 Π u .…”

Section: Introductionmentioning

confidence: 99%

“…(Ajello et al 2007;James et al 1990). For sufficiently energetic electron or proton collisions, a comparable amount of emission arises from the decay of excited atomic dissociation products (Ajello & Shemansky 1985;Ajello et al 1989Ajello et al , 2011aAjello et al , 2011b. Further electron-induced fluorescence occurs from the Lyman-Birge-Hopfield (LBH) series of bands originating from the a 1 Π g excited state.…”

Section: Introductionmentioning

confidence: 99%

“…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. The LBH molecular bands, the strongest band system in the far ultraviolet (FUV; 1200-2500 Å), excited by particle impact appear strongly in planetary atmospheres containing N 2 as a major species (Ajello et al 2011a).…”

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%

Section: Introductionmentioning

confidence: 99%

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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“…Electron interactions leading to molecular decomposition and synthesis within condensed matter are of relevance to problems in diverse fields such as biophysics [1][2][3][4], astrophysics and chemistry [5][6][7], nanotechnology [8][9][10], and material and environmental sciences [11][12][13][14]. Both analytical and Monte Carlo simulation methods are usually employed to quantitatively model the complex sequences of electron-induced processes occurring in condensed media.…”

Section: Introductionmentioning

confidence: 99%

Absolute cross section for low-energy-electron damage to condensed macromolecules: A case study of DNA

et al. 2012

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Cross sections (CSs) for the interaction of low-energy electrons (LEE) with condensed macromolecules are essential parameters for accurate modeling of radiation-induced molecular decomposition and chemical synthesis. Electron irradiation of dry nanometer-scale macromolecular solid films has often been employed to measure CSs and other quantitative parameters for LEE interactions. Since such films have thicknesses comparable with electron thermalization distances, energy deposition varies throughout the film. Moreover, charge accumulation occurring inside the films shields a proportion of the macromolecules from electron irradiation. Such effects complicate the quantitative comparison of the CSs obtained in films of different thicknesses and limit the applicability of such measurements. Here, we develop a simple mathematical model, termed the molecular survival model, that employs a CS for a particular damage process together with an attenuation length related to the total CS, to investigate how a measured CS might be expected to vary with experimental conditions. As a case study, we measure the absolute CS for the formation of DNA strand breaks (SBs) by electron irradiation at 10 and 100 eV of lyophilized plasmid DNA films with thicknesses between 10 and 30 nm. The measurements are shown to depend strongly on the thickness and charging condition of the nanometer-scale films. Such behaviors are in accord with the model and support its validity. Via this analysis, the CS obtained for SB damage is nearly independent of film thickness and charging effects. In principle, this model can be adapted to provide absolute CSs for electron-induced damage or reactions occurring in other molecular solids across a wider range of experimental conditions.

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Remote Sensing of Earth's Limb by TIMED/GUVI: Retrieval of thermospheric composition and temperature

Meier

Picone

Drob

et al. 2015

Earth and Space Science

122

276

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The Global Ultraviolet Imager (GUVI) onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite senses far ultraviolet emissions from O and N 2 in the thermosphere. Transformation of far ultraviolet radiances measured on the Earth limb into O, N 2 , and O 2 number densities and temperature quantifies these responses and demonstrates the value of simultaneous altitude and geographic information. Composition and temperature variations are available from 2002 to 2007. This paper documents the extraction of these data products from the limb emission rates. We present the characteristics of the GUVI limb observations, retrievals of thermospheric neutral composition and temperature from the forward model, and the dramatic changes of the thermosphere with the solar cycle and geomagnetic activity. We examine the solar extreme ultraviolet (EUV) irradiance magnitude and trends through comparison with simultaneous Solar Extreme EUV (SEE) measurements on TIMED and find the EUV irradiance inferred from GUVI averaged (2002-2007) 30% lower magnitude than SEE version 11 and varied less with solar activity. The smaller GUVI variability is not consistent with the view that lower solar EUV radiation during the past solar minimum is the cause of historically low thermospheric mass densities. Thermospheric O and N 2 densities are lower than the NRLMSISE-00 model, but O 2 is consistent. We list some lessons learned from the GUVI program along with several unresolved issues.

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UV Molecular Spectroscopy from Electron Impact for Applications to Planetary Atmospheres and Astrophysics

Cited by 16 publications

References 136 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

Absolute cross section for low-energy-electron damage to condensed macromolecules: A case study of DNA

Remote Sensing of Earth's Limb by TIMED/GUVI: Retrieval of thermospheric composition and temperature

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UV Molecular Spectroscopy from Electron Impact for Applications to Planetary Atmospheres and Astrophysics

Cited by 16 publications

References 136 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

Absolute cross section for low-energy-electron damage to condensed macromolecules: A case study of DNA

Remote Sensing of Earth's Limb by TIMED/GUVI: Retrieval of thermospheric composition and temperature

Contact Info

Product

Resources

About

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

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