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2 results

  • Theoretical Methods of Treating Line Formation Problems in Steady-State Extended Atmospheres

  • George B. Rybicki
  • Journal:
    International Astronomical Union Colloquium / Volume 2 / August 1970
    Published online by Cambridge University Press:
    08 February 2017, pp. 85-118
    Print publication:
    August 1970
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  • Theoretical methods applicable to the study of line formation in steady-state extended atmospheres are reviewed. The formal solution of the transfer equation is considered, as well as numerical and analytical methods of determining the source function. Topics discussed include: the local frequency transformation, geometrical effects, and the case of large velocity gradients. A new plane-parallel approximation for spherically symmetric moving atmospheres is given that takes account of transverse velocity gradients.

  • Laser Action in Non-LTE Atmospheres

  • Donald H. Menzel
  • Journal:
    International Astronomical Union Colloquium / Volume 2 / August 1970
    Published online by Cambridge University Press:
    08 February 2017, pp. 134-137
    Print publication:
    August 1970
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  • The radiative transfer equation is written in microscopic form, and from some simplifications on the ratio of occupation numbers for upper and lower level, a laser action is suggested.