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Investigation of a laboratory candidate for the carrier of the 4430 A diffuse interstellar bandThe 4430 A diffuse interstellar band (DIB) is unique among DIB's in that as one of the strong bands, it is the bluest strong band with no others observed at shorter wavelengths. This position at the edge of the DIF 'forrest' suggests it may be the easiest to replicate in the laboratory. In earlier experiments (Wdowiak 1980) an interesting candidate using a gas discharge followed by cryogenic matrix isolation was produced, and this report details its further investigation. This absorption feature, produced when 1 part CH4 in 200 parts Ar is discharged and frozen out approximately 10 K, is at a wavelength of 4500 A in the argon matrix. Our recent experiments strongly indicate it is due to a carbon-based reactive species that is stable against mercury vapor UV radiation, and not likely to be from a contaminant. The effect of matrix shift can be estimated by considering the blueward shift between Ar and Ne matrices in the cases of the pyrene and C60 cations. This suggests that a shift from 4500 A for an Af matrix to the vicinity of 4300 A for a Ne matrix and the gas phase is not unreasonable. A liquid He cooled Ne matrix isolation experiment was prepared to determine the wavelength of the feature in that matrix. Replacing CH4 with C2H2 results in an equivalent absorption due to C3, greatly diminished absorptions from C2 and Ch, and no observable feature at 4500 A. To date our experiments indicate CH4 is a favored precursor for production of the reactive carrier of the 4500 A feature. Perhaps C2H2 is not suitable because of its tendency to polymerize easily in the discharge.
Document ID
19950009425
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Wdowiak, Thomas J.
(Alabama Univ. Birmingham, AL, United States)
Beegle, Luther W.
(Alabama Univ. Birmingham, AL, United States)
Lee, Wei
(Alabama Univ. Birmingham, AL, United States)
Robinson, Michael S.
(Alabama Univ. Birmingham, AL, United States)
Date Acquired
September 6, 2013
Publication Date
May 1, 1994
Publication Information
Publication: NASA. Ames Research Center, The Diffuse Interstellar Bands: Contributed Papers
Subject Category
Astronomy
Accession Number
95N15840
Funding Number(s)
CONTRACT_GRANT: NAGW-3902
CONTRACT_GRANT: NAGW-749
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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