POLYCYCLIC AROMATIC HYDROCARBON CLUSTERS AS SOURCES OF INTERSTELLAR INFRARED EMISSION

Journal Article · Tue Mar 10 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/801/2/108· OSTI ID:22521383

Roser, J. E.

Polycyclic aromatic hydrocarbons (or PAHs) have been the subject of astrochemical research for several decades as principal sources of the interstellar aromatic infrared emission bands. PAH clusters could possibly contribute to these emission bands, but a lack of data on their infrared properties has made this hypothesis difficult to evaluate. Here we investigate homogeneous neutral PAH clusters by measuring the mid-infrared absorption spectra of the five nonlinear PAH molecules phenanthrene, chrysene, pyrene, perylene, and benzo[ghi]perylene within solid argon ice at a fixed temperature of 5 K. We attribute observed spectral shifts in their principal absorption bands as a function of argon/PAH ratio to clustering of the PAH molecules within the argon matrix. These shifts are related to the cluster structures forming in the matrix and the topology of the monomer PAH molecule. We predict that interstellar PAH molecules that are relatively large (no fewer than 50 carbon atoms per molecule) and compact will have clusters that contribute to the asymmetrically red-shaded profile of the interstellar 11.2 μm emission band.

• OSTI ID: 22521383
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 801; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION SPECTRA
ARGON
ATOMS
CHRYSENE
EMISSION SPECTRA
ICE
INTERMEDIATE INFRARED RADIATION
INTERSTELLAR SPACE
MOLECULES
MONOMERS
NONLINEAR PROBLEMS
PERYLENE
PHENANTHRENE
POLYCYCLIC AROMATIC HYDROCARBONS
PYRENE
SPECTRAL SHIFT