AAS 201st Meeting, January, 2003
Session 67. Cosmic Gas: Long Ago and Far Away
Oral, Tuesday, January 7, 2003, 2:00-3:30pm, 606-607

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[67.03U] Non-LTE Effects in Hydrogen Recombination Lines at the Epoch of Recombination

S. Daniel (Whitman Coll. & Maria Mitchell Obs.), V. Strelnitski (Maria Mitchell Obs.)

Previous studies of possible signatures left by the epoch of recombination in the Cosmic Background Radiation (CBR) indicated a strong disturbance produced in the original spectrum by the trapped L-alpha photons, but in the practically unobservable, far IR part of the contemporary CBR spectrum, in addition to very weak signatures produced by the higher n recombination lines in the observable, radio domain of the CBR. These studies did not consider possible amplification of the signatures by non-LTE effects in recombination lines. Yet, our recent theoretical study of the recombination/cascading process in hydrogen, stimulated by the discovery of the first hydrogen recombination line masers and lasers in the emission line star MWC349, suggests the possibility of both maser amplification and enhanced absorption ("dasar-effect") in hydrogen lines under the conditions of the epoch of recombination. We present here crude quantitative estimates of these effects and the results of the first numerical modeling of the recombination/cascading process in hydrogen at the epoch of recombination. We show that strong deviations from the Boltzmann distribution, including population inversion, are possible under these conditions for large groups of levels and that the maser and dasar effects can indeed amplify the signatures of recombination lines in the CBR, although these signatures still remain very weak (less or of the order of 0.01% of the black body intensity). This project was supported by the NSF/REU grant AST-0097694 and the Nantucket Maria Mitchell Association.

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