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Studies of Pressure-Broadening of Alkali Atom Resonance Lines for Modeling Atmospheres of Extrasolar Giant Planets and Brown DwarfsIn L-dwarfs and T-dwarfs the resonance lines of sodium and potassium are so profoundly pressure-broadened that their wings extend several hundred nanometers from line center. With accurate knowledge of the line profiles as a function of temperature and pressure: such lines can prove to be valuable diagnostics of the atmospheres of such objects. We have initiated a joint program of theoretical and experimental research to study the line-broadening of alkali atom resonance lines due to collisions with species such as helium and molecular hydrogen. Although potassium and sodium are the alkali species of most interest in the atmospheres of cool brown dwarfs and extrasolar giant planets, some of our theoretical focus this year has involved the calculation of pressure-broadening of lithium resonance lines by He, as a test of a newly developed suite of computer codes. In addition, theoretical calculations have been carried out to determine the leading long range van der Waals coefficients for the interactions of ground and excited alkali metal atoms with helium atoms, to within a probable error of 2%. Such data is important in determining the behavior of the resonance line profiles in the far wings. Important progress has been made on the experimental aspects of the program since the arrival of a postdoctoral fellow in September. A new absorption cell has been designed, which incorporates a number of technical improvements over the previous cell, including a larger cell diameter to enhance the signal, and fittings which allow for easier cleaning, thereby significantly reducing the instrument down-time.
Document ID
20040034769
Acquisition Source
Headquarters
Document Type
Contractor or Grantee Report
Authors
Kirby, Kate
(Smithsonian Astrophysical Observatory Cambridge, MA, United States)
Babb, J.
(Smithsonian Astrophysical Observatory Cambridge, MA, United States)
Yoshino, K.
(Smithsonian Astrophysical Observatory Cambridge, MA, United States)
Date Acquired
August 21, 2013
Publication Date
March 1, 2004
Subject Category
Astrophysics
Funding Number(s)
CONTRACT_GRANT: NAG5-12751
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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