J/ApJS/211/28 High resolution EUV spectrum of N2 (Heays+, 2014)
The high-resolution extreme-ultraviolet spectrum of N2 by electron impact.
Heays A.N., Ajello J.M., Aguilar A., Lewis B.R., Gibson S.T.
<Astrophys. J. Suppl. Ser., 211, 28 (2014)>
=2014ApJS..211...28H 2014ApJS..211...28H
ADC_Keywords: Atomic physics ; Spectra, ultraviolet ; Line Profiles
Keywords: line: identification; minor planets, asteroids: individual: Titan;
molecular data; planets and satellites: atmospheres;
radiation mechanisms: non-thermal; ultraviolet: general
Abstract:
We have analyzed high-resolution (FWHM=0.2Å) extreme-ultraviolet
(EUV, 800-1350Å) laboratory emission spectra of molecular nitrogen
excited by an electron impact at 20 and 100eV under (mostly) optically
thin, single-scattering experimental conditions. A total of 491
emission features were observed from N2 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
a1Πg, b1Πu, and b'1Σu+ excited valence
states and the Rydberg series c'n+11Σu+, cn1Πu,
and on1Πu for n between 3 and 9. The frequently blended
molecular emission bands were disentangled with the aid of a
sophisticated and predictive quantum-mechanical 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 100eV 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.
Description:
We have performed an absolutely calibrated high-resolution study of
the EUV emission spectrum of molecular nitrogen between 850 and
1150Å following electron excitation. Emission spectra were recorded
for low- and high-pressure N2 targets using an EUV spectrometer,
with 20 and 100eV impact energies. Nearly all of the observed
molecular bands are optically thin and correspond to single-scattering
events.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 73 538 Experimental results
--------------------------------------------------------------------------------
See also:
J/A+A/559/A114 : O3N2 and N2 abundance indicators revisited (Marino+, 2013)
J/A+A/439/387 : Absolute photoionization cross sections (Bizau+, 2005)
J/A+AS/128/361 : Vacuum ultraviolet emission band systems of N2 (Roncin+ 1998)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 29 A29 --- Line Assignment
31- 38 F8.3 0.1nm lambda [806/1347] Peak wavelength; in Angstroms
40- 45 F6.3 10-20cm2 CS20 [0.01/51.6]? Emission cross section at 20eV
47- 51 F5.3 10-20cm2 e_CS20 [0.009/0.9]? One sigma uncertainty in CS20
53- 55 A3 --- n_CS20 Note(s) on CS20 (1)
57- 63 F7.3 10-20cm2 CS100 [0.05/178]? Emission cross section at 100eV
65- 69 F5.3 10-20cm2 e_CS100 [0.02/4]? One sigma uncertainty in CS100
71- 73 A3 --- n_CS100 Note(s) on CS100 (1)
--------------------------------------------------------------------------------
Note (1): Note as follows:
1 = Line-by-line model.
2 = Significantly self-absorbed.
3 = Enhanced because of self absorption of c'4(0,0).
4 = Intensity is calculated from a direct integration and not a
modelled band profile.
5 = To allow for the fitting of overlapping features the intensity
of this band was assumed.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 07-May-2014