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Interstellar gas clouds, the birthplaces of stars, are known to harbour a wealth of complex organic molecules. Barrier less reactions starting from rather simple molecular ions are the main drivers of the chemistry in these cold regions of space, leading to an increasing level of chemical complexity.


Spectroscopic fingerprints

Laboratory experiments providing spectroscopic fingerprint data on key intermediates in this interstellar chemistry are crucial for their detection in space, and to interpret the astronomical observations. However, reactive molecular ions are extremely difficult to investigate by standard spectroscopic techniques. We established a novel spectroscopic method to acquire high-resolution rotational spectra of molecular ions under isolated conditions in a cryogenic ion trap instrument. Complementary data on their vibrational spectra can be obtained using the FELIX infrared free electron lasers. In this way the spectroscopic fingerprints of a large class of astrophysically important ionic species will be obtained, providing the necessary data for their identification in space.

IR spectra

We have a long history in the recording of IR spectra for ionized carbonaceous molecules that are hypothesized to occur in inter- and circumstellar clouds. They especially studied a large number of polyaromatic molecules in their radical cation, protonated and negatively charged forms. More recently, using the Bruker Amazon ion trap, we have begun to study charged fullerenes.

Due to their high stability, the structural characterisation of some species using FELIX has been difficult. The Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FTICR MS) installed within the cavity of the Free Electron Laser for Intra-Cavity Experiments, FELICE, allows the study of these highly stable species.

The FELion cryogenic 22-pole ion trap instrument, designed and built in Cologne in collaboration with the FELIX team, allows the gas-phase spectroscopic characterization of mass-selected, internally and kinetically cold (T > 4 K) molecular ions by different action spectroscopic methods. We have studied astrophysically important cations, ranging in size from comparatively small systems (e.g., CnHm+, n=1-3, m=0-3; CnHmN+, n=2,3, m=1-6) to larger systems like PAHs (e.g., C10H8+(++), C17H11+).

Other pages

Articles describing the three setups

FELion cryogenic 22-pole ion trap

The FELion cryogenic ion trap beam line at the FELIX free-electron laser laboratory: infrared signatures of primary alcohol cations.
J. Pavel, S. Brünken, O. Asvany, S. Thorwirth, A. Stoffels, L. van der Meer, G. Berden, B. Redlich, J. Oomens, and S. Schlemmer
Faraday Discussions 217 (2019) 172-202.
© 2019 Royal Society of Chemistry. (pdf file)

Bruker Amazon ion trap

Infrared ion spectroscopy in a modified quadrupole ion trap mass spectrometer at the FELIX free electron laser laboratory.
J. Martens, G. Berden, C.R. Gebhardt, and J. Oomens
Review of Scientific Instruments 88 (2016) 6126–6129.
© 2016 American Institute of Physics. Review of Scientific Instruments (2016)

FELICE intracavity FTICR ion trap

Breakdown products of gaseous polycyclic aromatic hydrocarbons investigated with infrared ion spectroscopy.
A. Petrignani, M. Vala, J.R. Eyler, A.G.G.M. Tielens, G. Berden, A.F.G. van der Meer, B. Redlich, and J. Oomens
The Astrophysical Journal 826 (2016) 33.
© 2016 The American Astronomical Society. The Astrophysical Journal (2016)