Astrophysical lasers operating in optical Fe II lines in stellar ejecta of η Carinae
(2004) In Astronomy & Astrophysics 428. p.497-509- Abstract
- After the discovery of space masers based on OH radicals (Weaver et al.cite{Wea65}) and H<SUB>2</SUB>O (Cheung et al. cite{Che69}) such microwavelasers have been found to work in more than 100 molecular species(Elitzur cite{Eli92}; Townes cite{Tow97}), as well as in highlyexcited H atoms (Strelnitski et al. cite{Str96}). In the IR region (10mum), the effect of stimulated emission of radiation in the CO<SUB>2</SUB>molecule has been discovered in the Martian and Venus' atmospheres (Betzet al. cite{Bet76}; Mumma et al. cite{Mum81}). We report here on thediscovery of laser action in the range 0.9-2 μm in several spectrallines of Fe II, which are associated with transitions from``pseudo-metastable'' states populated by... (More)
- After the discovery of space masers based on OH radicals (Weaver et al.cite{Wea65}) and H<SUB>2</SUB>O (Cheung et al. cite{Che69}) such microwavelasers have been found to work in more than 100 molecular species(Elitzur cite{Eli92}; Townes cite{Tow97}), as well as in highlyexcited H atoms (Strelnitski et al. cite{Str96}). In the IR region (10mum), the effect of stimulated emission of radiation in the CO<SUB>2</SUB>molecule has been discovered in the Martian and Venus' atmospheres (Betzet al. cite{Bet76}; Mumma et al. cite{Mum81}). We report here on thediscovery of laser action in the range 0.9-2 μm in several spectrallines of Fe II, which are associated with transitions from``pseudo-metastable'' states populated by spontaneous transitions fromLyα pumped Fe II levels. The intense Lyα radiation is formedin the HII region of gas condensations close to the star η Car. Thelaser transitions form together with spontaneous transitions closedradiative cycles, one of which includes the extremely bright 2507/09Å lines. Closed radiative cycles, together with an accidentalmixing of energy levels, may provide an explanation of the abnormalintensities of these UV non-lasing lines. Using the complicated energylevel diagram of Fe II we present those peculiar features, which areessential for the inverted population and laser effect: the pumping, thelevel mixing, and the ``bottle neck'' for spontaneous decay. The laseraction is a new indicator of non-equilibrium and spatiallynon-homogeneous physical conditions as well as a high brightnesstemperature of Lyα in ejecta from eruptive stars. Such conditionsare very difficult to probe by existing methods, and we propose somefuture experiments. The fact, that the lasing near-IR lines appear inthe spectrum with about the same intensity as non-lasing lines isdiscussed and compared with the situation in masers. (Less)
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https://lup.lub.lu.se/record/134074
- author
- Johansson, Sveneric LU and Letokhov, Vladilen LU
- organization
- publishing date
- 2004
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- atomic processes, line: formation, radiation mechanisms: non-thermal, stars: individual: η Carinae
- in
- Astronomy & Astrophysics
- volume
- 428
- pages
- 497 - 509
- publisher
- EDP Sciences
- external identifiers
-
- wos:000225335100014
- scopus:10844246213
- ISSN
- 0004-6361
- DOI
- 10.1051/0004-6361:20040379
- language
- English
- LU publication?
- yes
- id
- 2fe01eb4-e299-4b05-b7a5-477cb2b6daf2 (old id 134074)
- date added to LUP
- 2016-04-01 17:02:49
- date last changed
- 2024-01-11 19:38:12
@article{2fe01eb4-e299-4b05-b7a5-477cb2b6daf2,
abstract = {{After the discovery of space masers based on OH radicals (Weaver et al.cite{Wea65}) and H<SUB>2</SUB>O (Cheung et al. cite{Che69}) such microwavelasers have been found to work in more than 100 molecular species(Elitzur cite{Eli92}; Townes cite{Tow97}), as well as in highlyexcited H atoms (Strelnitski et al. cite{Str96}). In the IR region (10mum), the effect of stimulated emission of radiation in the CO<SUB>2</SUB>molecule has been discovered in the Martian and Venus' atmospheres (Betzet al. cite{Bet76}; Mumma et al. cite{Mum81}). We report here on thediscovery of laser action in the range 0.9-2 μm in several spectrallines of Fe II, which are associated with transitions from``pseudo-metastable'' states populated by spontaneous transitions fromLyα pumped Fe II levels. The intense Lyα radiation is formedin the HII region of gas condensations close to the star η Car. Thelaser transitions form together with spontaneous transitions closedradiative cycles, one of which includes the extremely bright 2507/09Å lines. Closed radiative cycles, together with an accidentalmixing of energy levels, may provide an explanation of the abnormalintensities of these UV non-lasing lines. Using the complicated energylevel diagram of Fe II we present those peculiar features, which areessential for the inverted population and laser effect: the pumping, thelevel mixing, and the ``bottle neck'' for spontaneous decay. The laseraction is a new indicator of non-equilibrium and spatiallynon-homogeneous physical conditions as well as a high brightnesstemperature of Lyα in ejecta from eruptive stars. Such conditionsare very difficult to probe by existing methods, and we propose somefuture experiments. The fact, that the lasing near-IR lines appear inthe spectrum with about the same intensity as non-lasing lines isdiscussed and compared with the situation in masers.}},
author = {{Johansson, Sveneric and Letokhov, Vladilen}},
issn = {{0004-6361}},
keywords = {{atomic processes; line: formation; radiation mechanisms: non-thermal; stars: individual: η Carinae}},
language = {{eng}},
pages = {{497--509}},
publisher = {{EDP Sciences}},
series = {{Astronomy & Astrophysics}},
title = {{Astrophysical lasers operating in optical Fe II lines in stellar ejecta of η Carinae}},
url = {{https://lup.lub.lu.se/search/files/4858320/624406.pdf}},
doi = {{10.1051/0004-6361:20040379}},
volume = {{428}},
year = {{2004}},
}