Physics – Atomic Physics
Scientific paper
May 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005aipc..770..399j&link_type=abstract
ATOMIC PHYSICS 19: XIX International Conference on Atomic Physics; ICAP 2004. AIP Conference Proceedings, Volume 770, pp. 399-4
Physics
Atomic Physics
Magnetohydrodynamics And Plasmas, Emission-Line Stars, Luminosities, Magnitudes, Effective Temperatures, Colors, And Spectral Classification, Spectroscopy And Spectrophotometry
Scientific paper
We report here on the discovery of laser action in the range 0.9-2 μm in several spectral lines of Fe II, which are associated with transitions from ``pseudo-metastable'' states populated by spontaneous transitions from Lyα pumped Fe II levels. The intense Lyα radiation is formed in the HII region of gas condensations close to the star η Car. The laser transitions form together with spontaneous transitions closed radiative cycles, one of which includes the extremely bright 2507/09 Å lines. This fact, together with an accidental mixing of energy levels, may provide an explanation of the abnormal intensities of these UV non-lasing lines. Using the complicated energy level diagram of Fe II we present those peculiar features, which are essential for the inverted population and laser effect: the pumping, the level mixing, and the ``bottle neck'' for spontaneous decay. The laser action is a new indicator of non-equilibrium and spatially non-homogeneous physical conditions as well as a high brightness temperature of Lyα in ejecta from eruptive stars. Such conditions are very difficult to probe by existing methods.
Johansson Sara
Letokhov V. S.
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