New clues to the impact broadening mystery in radio recombination lines

  1. Get@NRC: New clues to the impact broadening mystery in radio recombination lines (Opens in a new window)
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Journal titleAstrophysics and Space Science
Pages451456; # of pages: 6
AbstractProblems where impact broadened radio recombination lines appeared narrower than predicted first showed up ~40 years ago at frequencies below ~3 GHz. But it was soon found that the observations could be explained by throwing out the uniform density models and replacing them with variable density ones. However, this problem re-appeared recently when a mysterious line narrowing above quantum numbers of (n,Δn)=(202,8) was reported from sensitive observations of Orion and W51 near 6 GHz. Here it is demonstrated that the narrowing is unlikely to be caused by the data processing technique and therefore must be source related. It is further demonstrated that the observed line narrowing can be tied to one of the fundamental properties of radio recombination lines; namely the fact that the spacing of adjacent n-transitions increases with frequency. The line narrowing is observed to begin when the n-transition density, Dn, exceeds ~11. 6 transitions per GHz. This may imply that it is somehow related either to a previously overlooked effect in the impact broadening process, or to some unknown parallel process, that is tied to the separation between adjacent n-transitions. Based on these results it can be concluded, as has also been concluded in several theoretical investigations, that the observed line narrowing is not tied to a fixed range of either n or Δn. © 2011 Her Majesty the Queen in Right of Canada.
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AffiliationNational Research Council Canada (NRC-CNRC); NRC Herzberg Institute of Astrophysics (HIA-IHA)
Peer reviewedYes
NPARC number21271130
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Record identifierc38d1ab4-f0c1-4bf8-995c-f3a80eef970a
Record created2014-03-24
Record modified2016-05-09
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