Astrophysics and Space Science

, Volume 36, Issue 2, pp 291–301 | Cite as

Population of excited rotational levels of HD and CO in interstellar clouds

  • Pushpa Joshi
  • S. P. Tarafdar


Populations of the rotational levels of vibrational and electronic ground state of interstellar HD and CO have been calculated. Ultraviolet pumping and molecular formation have been found to be very important in the case of HD but not so in CO, the population distribution of which is mainly governed either by 3 K or by collisional excitation. The population inversion has been found to occur in HD but not in CO, the excitation temperatures of which pass through maximum for large ultraviolet flux. The population inversion at large density does not occur in HD, probably due to neglect of multipole collision. The observation of HD and CO in the excited states may be possible for suitable values of density and ultraviolet flux.


Excited State Population Distribution Molecular Formation Large Density Electronic Ground State 
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Copyright information

© D. Reidel Publishing Company 1975

Authors and Affiliations

  • Pushpa Joshi
    • 1
  • S. P. Tarafdar
    • 2
  1. 1.Tata Institute of Fundamental ResearchBombayIndia
  2. 2.Dept. of Applied Mathematics and AstronomyUniversity CollegeCardiffUK

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