The Search for Carriers of Diffuse Interstellar Bands (I 4130)

funded by FWF

Principal Investigator: Paul Scheier
Duration: 01.05.2019 - 31.07.2022 (Approval date: 01.10.2018)
Scientific fields: 70% 103 Physik, Astronomie
30% 104 Chemie
Keywords: photo dissocation, helium droplets, diffuse interstellar bands, messenger type spectroscopy, matrix isolation, helium tagging


Absorption spectra of several polycyclic aromatic hydrocarbon (PAH) ions were measured in the visible and near infrared range and compared to astronomical observations. We obtained these spectra via photodissociation of He tagged ions that were formed inside helium droplets containing typically a few million He atoms. The absorption lines of none of the investigated ions match diffuse interstellar bands found in astronomical observations. Along these studies, we discovered and developed a novel pathway to produce most efficiently He tagged ions of both polarities upon pickup of dopants into charged helium droplets and subsequent collisions of these droplets with a clean metal surface. This enables messenger type spectroscopy of ions that have not been accessible so far, such as anions and complex cluster ions.

Final Report (PDF)

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