Astronomy and Astrophysics – Astrophysics
Scientific paper
Sep 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994aas...184.2907t&link_type=abstract
American Astronomical Society, 184th AAS Meeting, #29.07; Bulletin of the American Astronomical Society, Vol. 26, p.902
Astronomy and Astrophysics
Astrophysics
Scientific paper
This paper discusses the possibility that the intensities of the [N II] emission lines at 6548 and 6584 Angstroms are boosted, in a variety of astrophysical nebulae, by the (2s(2}2p({2)) ) \ (1}D_{2) --- (2s(2) 2p3s) \ (3}P({o}_{1)) transition at 748 Angstroms. According to theoretical calculations by Fawcett and experimental measurement of the branching ratio, this intersystem (Delta S !=q 0) transition is as fast as a typical electric dipole allowed transition. The (2s(2) 2p3s) \ (3}P({o}_{1)) level is directly populated by a resonance transition from the (2s(2}2p({2)) ) \ (3) P ground state, and one out of three electrons that enter the (2s(2) 2p3s) \ (3}P({o}_{1)) level will spontaneously decay through the 748 Angstroms \ transition. Since the 748 Angstroms transition deposits electrons in the (2s(2}2p({2)) ) \ (1}D_{2) level from which the [N II] lambda lambda 6548,6584 emissions originate, this remarkably strong intersystem transition will increase the intensities of the famous [N II] temperature diagnostic emission lines if significant excitation of the (2s(2) 2p3s) \ (3}P({o}_{1)) level occurs. We discuss the circumstances in which the (3s) \ (3}P({o}_{1)) upper level could be significantly populated by photoexcitation, collisional excitation, or recombination. We point out that detection of recombination lines that feed the (3s) \ (3}P({o}_{1)) level provides direct evidence that this process is important in nova shells. We also discuss the possible importance of this process in the production of anomalously large [N II]/Hα ratios in cooling flow emission line filaments and starburst galaxy superwinds.
Tripp Todd M.
Watson Alan Andrew
~Gallagher John S.
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