Harald Knorke et al 2009 ApJ 706 L66 doi:10.1088/0004-637X/706/1/L66
Harald Knorke1, Judith Langer1, Jos Oomens2,3 and Otto Dopfer1
Show affiliationsGas-phase infrared (IR) spectra of larger protonated polycyclic aromatic hydrocarbon molecules, H+PAH, have been recorded for the first time. The ions are generated by electrospray ionization and spectroscopically assayed by IR multiple-photon dissociation (IRMPD) spectroscopy in a Fourier transform ion cyclotron resonance mass spectrometer using a free electron laser. IRMPD spectra of protonated anthracene, tetracene, pentacene, and coronene are presented and compared to calculated IR spectra. Comparison of the laboratory IR spectra to an astronomical spectrum of the unidentified IR emission (UIR) bands obtained in a highly ionized region of the interstellar medium provides for the first time compelling spectroscopic support for the recent hypothesis that H+PAHs contribute as carriers of the UIR bands.
astrochemistry; infrared: ISM; ISM: molecules; methods: laboratory; molecular data; techniques: spectroscopic
33.80.Gj Diffuse spectra; predissociation, photodissociation
95.85.Hp Infrared (3–10 &mgr;m)
98.58.Db Molecular clouds, H2 clouds, dense clouds, and dark clouds
Issue 1 (2009 November 20)
Received 2009 August 27, accepted for publication 2009 October 13
Published 2009 October 30
Harald Knorke et al 2009 ApJ 706 L66
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