Synchrotron‐Based Rotationally Resolved High‐Resolution FTIR Spectroscopy of Azulene and the Unidentified Infrared Bands of Astronomy

Abstract

Chasing the unidentified IR bands: The first rotationally resolved high-resolution infrared spectrum of azulene is reported using synchrotron Fourier transform infrared spectroscopy including a rovibrational analysis of the out-of-plane fundamental ν44. Comparison of azulene, naphthalene, indole, and biphenyl infrared bands leads to coincidences with UIR bands at 12.8 μm with naphthalene and at 13.55 and 14.6 μm with biphenyl bands, but excluding azulene as a strong absorber.

Synchrotron-based highest resolution FTIR spectroscopy of chlorobenzene

“…Our analysis of chlorobenzene's FTIR spectrum is a further extension of our project to understand the dynamics and spectroscopy of aromatic systems. Compared to the complicated FTIR spectra of fluorobenzene [33,41], pyridine [50], pyrimidine [64], indole, naphthalene [3], azulene [8] and phenol [7] the chlorobenzene spectra are relatively easy to understand as long as the lines are resolved. No complicated resonance features have been detected.…”

“…The use of synchrotron radiation sources has greatly enhanced the possibilities of highest resolution Fourier Transform Infrared spectroscopy of polyatomic molecules [1][2][3][4][5][6][7][8][9][10][11]. In recent work we have shown that the infrared spectra of molecules as complex as naphthalene [3], azulene [8] and indene [10] can be rotationally resolved and analyzed, which can help the search for the spectra of such molecules in an astrophysical context.…”

“…In recent work we have shown that the infrared spectra of molecules as complex as naphthalene [3], azulene [8] and indene [10] can be rotationally resolved and analyzed, which can help the search for the spectra of such molecules in an astrophysical context. Furthermore tunneling dynamics in excited vibrational states of aromatic molecules such as phenol isotopomers can be studied successfully [7].…”

Survey of the high resolution infrared spectrum of methane (12CH4 and 13CH4): Partial vibrational assignment extended towards 12 000 cm−1

“…71,[85][86][87][88][89] The nominal instrumental resolution, defined by 1/d MOPD (maximum optical path difference) ranged from 0.0027 to 0.01 cm −1 resulting in almost Doppler limited spectra. The Doppler widths at 78 K range from about 0.004 cm −1 at 2800 cm −1 to 0.02 cm −1 at 12 500 cm −1 .…”

Physikalische Chemie 2013

“…Die Ursache der interstellaren, bisher nicht identifizierten Infrarotbanden (Unidentified Infrared Bands, UIBs) könnten Emissionen im infraroten Spektralbereich großer polyzyklischer aromatischer Kohlenwasserstoffe sein 115. In diesem Zusammenhang untersuchten wir die Absorptionsspektren einfacher Aromaten wie Pyridin11 und Pyrimidin116 sowie bicyclischer Aromaten wie Naphthalin,14,114 Indol,14 Azulen16 und Biphenyl 117. Mit Synchrotronstrahlung ist es möglich, die FTIR‐Spektren dieser Moleküle rotationsaufgelöst zu messen, wie das Naphthalinspektrum in Abbildung 1 (oben) zeigt.…”