IDENTIFICATION OF H{sub 2}CCC AS A DIFFUSE INTERSTELLAR BAND CARRIER

Journal Article · Sat Jan 01 04:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/726/1/41· OSTI ID:21567693

Maier, J P; Mazzotti, F J; Raghunandan, R; Fulara, J; Garkusha, I; Nagy, A ^[1]; Walker, G A. H. ^[2]

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1. Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel (Switzerland)
2. 1234 Hewlett Place, Victoria, BC V8S 4P7 (Canada)

We present strong evidence that the broad, diffuse interstellar bands (DIBs) at 4881 and 5450 A are caused by the B{sup 1} B{sub 1} <- X{sup 1} A{sub 1} transition of H{sub 2}CCC (l-C{sub 3}H{sub 2}). The large widths of the bands are due to the short lifetime of the B{sup 1} B{sub 1} electronic state. The bands are predicted from absorption measurements in a neon matrix and observed by cavity ring-down in the gas phase and show exact matches to the profiles and wavelengths of the two broad DIBs. The strength of the 5450 A DIB leads to a l-C{sub 3}H{sub 2} column density of {approx}5 x 10{sup 14} cm{sup -2} toward HD 183143 and {approx}2 x 10{sup 14} cm{sup -2} to HD 206267. Despite similar values of E(B - V), the 4881 and 5450 A DIBs in HD 204827 are less than one-third their strength in HD 183143, while the column density of interstellar C{sub 3} is unusually high for HD 204827 but undetectable for HD 183143. This can be understood if C{sub 3} has been depleted by hydrogenation to species such as l-C{sub 3}H{sub 2} toward HD 183143. There are also three rotationally resolved sets of triplets of l-C{sub 3}H{sub 2} in the 6150-6330 A region. Simulations, based on the derived spectroscopic constants and convolved with the expected instrumental and interstellar line broadening, show credible coincidences with sharp, weak DIBs for the two observable sets of triplets. The region of the third set is too obscured by the {alpha}-band of telluric O{sub 2}.

• OSTI ID: 21567693
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 726; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CHEMICAL REACTIONS
DENSITY
ELEMENTS
FLUIDS
GASES
HYDROGENATION
LINE BROADENING
MULTIPLETS
NEON
NONMETALS
PHYSICAL PROPERTIES
RARE GASES
SIMULATION
TRIPLETS