H2CCC - A Diffuse Interstellar Band Carrier
Abstract
We present strong evidence that the broad, diffuse interstellar bands (DIBs) at 4881 and 5450 Å are caused by the B1B1 ← X1A1 transition of H2CCC ({l}-C3H2). The vibronic bands of H2CCC are recorded by mass selected absorption measurements in a neon matrix. The matrix studies serve for the identification of 201 and 202 B1B1 ← X1A1 transitions in the gas phase by cavity ring-down measurements. The bands are broad, without any rotational structure. This arises due to the short lifetime of the B1B1 electronic state as a result of the fast intramolecular relaxation process to the nearby lying A1A2 state. These broad bands in gas phase are identified as H2CCC based on the matrix to gas wavelength shifts, deuteration and precursor tests. The gas phase laboratory spectra show excellent agreement to the profiles and wavelengths of the two broad DIBs observed in the astronomical spectra acquired at the Dominion Astrophysical Observatory with the 1.2 and 1.8 m telescopes at a resolution of R = 18,000 in early 2010.
- Publication:
-
The Molecular Universe
- Pub Date:
- May 2011
- Bibcode:
- 2011IAUS..280E..65R