Search for corannulene (C ₂₀H ₁₀) in the Red Rectangle

authored by: P. Pilleri, D. Herberth, T. F. Giesen, M. Gerin, C. Joblin, G. Mulas, G. Malloci, J. U. Grabow, S. Brünken, L. Surin, B. D. Steinberg, K. R. Curtis, L. T. Scott
Abstract: Polycyclic Aromatic Hydrocarbons (PAHs) are widely accepted as the carriers of the Aromatic Infrared Bands (AIBs), but an unambiguous identification of any specific interstellar PAH is still missing. For polar PAHs, pure rotational transitions can be used as spectral fingerprints for identification. Combining dedicated experiments, detailed simulations and observations, we explore d the mm wavelength domain to search for specific rotational transitions of corannulene (C ₂₀H ₁₀). We performed high-resolution spectroscopic measurements and a simulation of the emission spectrum of ultraviolet-excited C ₂₀H ₁₀ in the environment of the Red Rectangle (RR), calculating its synthetic rotational spectrum. Based on these results, we conducted a first observational campaign at the IRAM 30-m telescope towards this source to search for several high-J rotational transitions of C ₂₀H ₁₀. The laboratory detection of the J = 112 ← 111 transition of corannulene showed that no centrifugal splitting is present up to this line. Observations with the IRAM 30-m telescope towards the RR do not show any corannulene emission at any of the observed frequencies, down to a rms noise level of T _mb = 8 mK for the J =135 → 134 transition at 137.615 GHz. Comparing the noise level with the synthetic spectrum, we are able to estimate an upper limit to the fraction of carbon locked in corannulene of about 1.0 × 10 ^-5 relative to the total abundance of carbon in PAHs. The sensitivity achieved in this work shows that radio spectroscopy can be a powerful tool to search for polar PAHs. We compare this upper limit with models for the PAH size distribution, emphasizing that small PAHs are much less abundant than predicted. We show that this cannot be explained by destruction but is more likely related to the chemistry of their formation in the environment of the RR.
Organisation(s): Institute of Physical Chemistry and Electrochemistry
External Organisation(s): Universite Toulouse III - Paul Sabatier (UT3)
Observatoire de Paris (OBSPARIS)
University of Cologne
Istituto Nazionale di Astrofisica (INAF)
École polytechnique fédérale de Lausanne (EPFL)
Boston College
Type: Article
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 397
Pages: 1053-1060
No. of pages: 8
ISSN: 0035-8711
Publication date: 08.2009
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Electronic version(s): https://doi.org/10.1111/j.1365-2966.2009.15067.x (Access: Closed)

BibTeX

@article{51b755a2ee944fcb876097c4282c6aa3,
title = "Search for corannulene (C 20H 10) in the Red Rectangle",
abstract = "Polycyclic Aromatic Hydrocarbons (PAHs) are widely accepted as the carriers of the Aromatic Infrared Bands (AIBs), but an unambiguous identification of any specific interstellar PAH is still missing. For polar PAHs, pure rotational transitions can be used as spectral fingerprints for identification. Combining dedicated experiments, detailed simulations and observations, we explore d the mm wavelength domain to search for specific rotational transitions of corannulene (C 20H 10). We performed high-resolution spectroscopic measurements and a simulation of the emission spectrum of ultraviolet-excited C 20H 10 in the environment of the Red Rectangle (RR), calculating its synthetic rotational spectrum. Based on these results, we conducted a first observational campaign at the IRAM 30-m telescope towards this source to search for several high-J rotational transitions of C 20H 10. The laboratory detection of the J = 112 ← 111 transition of corannulene showed that no centrifugal splitting is present up to this line. Observations with the IRAM 30-m telescope towards the RR do not show any corannulene emission at any of the observed frequencies, down to a rms noise level of T mb = 8 mK for the J =135 → 134 transition at 137.615 GHz. Comparing the noise level with the synthetic spectrum, we are able to estimate an upper limit to the fraction of carbon locked in corannulene of about 1.0 × 10 -5 relative to the total abundance of carbon in PAHs. The sensitivity achieved in this work shows that radio spectroscopy can be a powerful tool to search for polar PAHs. We compare this upper limit with models for the PAH size distribution, emphasizing that small PAHs are much less abundant than predicted. We show that this cannot be explained by destruction but is more likely related to the chemistry of their formation in the environment of the RR.",
keywords = "Astrochemistry, ISM: abundances, ISM: individual: Red Rectangle, ISM: lines and bands, ISM: molecules",
author = "P. Pilleri and D. Herberth and Giesen, {T. F.} and M. Gerin and C. Joblin and G. Mulas and G. Malloci and Grabow, {J. U.} and S. Br{\"u}nken and L. Surin and Steinberg, {B. D.} and Curtis, {K. R.} and Scott, {L. T.}",
year = "2009",
month = aug,
doi = "10.1111/j.1365-2966.2009.15067.x",
language = "English",
volume = "397",
pages = "1053--1060",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "2",
}

Search for corannulene (C 20H 10) in the Red Rectangle

Search for corannulene (C ₂₀H ₁₀) in the Red Rectangle