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Laboratory Detection of a Molecular Band at lambda4429
The Astrophysical Journal
|December 30, 1999
Summary
Researchers identified a molecular absorption band matching a diffuse interstellar band, suggesting a common carrier. Potential candidates include the allyl cation (C3H+5) and dimethylene allenyl radical (C5H5).
Area of Science:
- Astrochemistry
- Molecular Spectroscopy
- Interstellar Medium
Background:
- Diffuse interstellar bands (DIBs) are absorption features in astronomical spectra.
- The carriers of most DIBs remain unidentified, hindering our understanding of interstellar chemistry.
Purpose of the Study:
- To investigate the molecular carrier of the strong diffuse interstellar band at 4428.9 Å.
- To compare laboratory spectral data with astronomical observations.
Main Methods:
- Generating molecular species in a supersonic molecular beam via electrical discharge through hydrocarbons (e.g., benzene).
- Measuring high-resolution absorption spectra of the produced molecules.
- Comparing laboratory band wavelengths and isotopic shifts with the 4428.9 Å DIB.
Main Results:
- A strong molecular absorption band was detected at 4429.27 ± 0.04 Å, closely matching the DIB wavelength.
- The laboratory band's narrower width suggests a lower rotational temperature (≈2 K) compared to interstellar conditions (100-200 K).
- Candidate carriers, allyl cation (C3H+5) and dimethylene allenyl radical (C5H5), were proposed based on spectral and isotopic evidence.
Conclusions:
- The close wavelength match strongly suggests a common molecular carrier for the observed laboratory band and the 4428.9 Å DIB.
- The proposed bent carbon chain molecules (C3H+5, C5H5) are plausible candidates for interstellar DIB carriers.
- Further spectroscopic studies are needed to confirm the carrier identity.