THE INFRARED SPECTRUM OF PROTONATED NAPHTHALENE AND ITS RELEVANCE FOR THE UNIDENTIFIED INFRARED BANDS

Journal Article · Tue Sep 01 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/702/1/301; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21333852

Ricks, Allen M; Douberly, Gary E ^[1]

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1. Department of Chemistry, University of Georgia, Athens, GA 30602 (United States)

The gas phase infrared spectrum of protonated naphthalene is measured in a cold supersonic beam using mass-selected photodissociation spectroscopy and the messenger atom method. Sharp vibrational band structure is measured throughout the 800-3200 cm{sup -1} region for comparison to the unidentified infrared bands (UIRs). Protonated naphthalene exhibits strong bands at 3.5, 6.2, 7.7, and 8.6 {mu}m that correspond to prominent UIR features. The 6.2 {mu}m feature provides one of the first examples in laboratory spectra for an intense vibrational band at this wavelength. It arises from an 'allyl-type' carbon ring distortion, which is a direct consequence of the perturbation on aromatic rings resulting from protonation in the {sigma} configuration. The 3.5 and 7.7 {mu}m features correspond to the stretches and scissors motion of the aliphatic CH{sub 2} group, which also follow directly from protonation. Other strong bands seen at 6.6 and 6.9 {mu}m do not coincide with the strongest UIR features. Protonated naphthalene itself is not a perfect match for the UIR spectra, but it strongly suggests that larger H{sup +}PAH species are prominent among the UIR carriers.

• OSTI ID: 21333852
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 702; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
CARBON
DISSOCIATION
INFRARED SPECTRA
NAPHTHALENE
PERTURBATION THEORY
PHOTOLYSIS
POLYCYCLIC AROMATIC HYDROCARBONS
SPECTROSCOPY
VIBRATIONAL STATES