The Search for Carriers of Diffuse Interstellar Bands

• Applicant: Dr. Sergiy Krasnokutskiy
• Subject Area: Astrophysics and Astronomy ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 413610339

Wider research context Diffuse interstellar bands (DIBs) are absorption features of dense areas of the interstellar medium (ISM) observed in the visible and near-infrared ranges. To identify the carriers of DIBs, we suggest to measure absorption lines of several classes of molecules that were predicted or proven to exist in astrophysical environments.Objectives The main attention will be given to long carbon chains (>15 C atoms). In spite of being promising candidates for the role of DIB carriers, their spectra have never been measured since their production by bottom-up chemistry at high temperatures is limited to small chains. Although the spectroscopy of short carbon chains was intensely studied, and no absorption bands of these molecules besides C3 were found in the ISM, all these studies probed only first electronic transitions, which are quite weak. The increase of the carbon chain length brings strong absorption bands in the position where DIBs are detected and the intensity of these strong bands are at least two orders of magnitude higher compared to the previously studied transitions. Thus even moderate abundances of these species in the ISM would provide an absorption that can be detected.Methods We will use experimental techniques developed in the previous joint project that allows us to considerably improve the quality and speed of spectral data collection. This technique of cation spectroscopy provides data of cold cations in a quality necessary for the direct comparison with astrophysical observations, at a much higher rate compared to other currently existing experimental methods. This makes it possible to test a larger number of species and consequently increases the chances to identify new carriers of DIBs.Level of originalityThe use of the He droplet technique will allow the measurement of radicals that are formed either by low-temperature chemistry or via fragmentation of parent molecules during the ionization. This provides access to species that are hard or impossible to measure in other ways. Knowledge of the oscillator strength of electronic transition corresponding to absorption bands, which are not detected in astronomical observations, allows estimating an upper limit of the abundance of the corresponding species in the ISM. This provides useful information on the chemistry occurring in these areas and on the probability that other molecules from the same class can be detected in the same areas. All these expected results bring the currently proposed attempt of identification of carriers of DIBs to a completely new level.Primary researchers involved The proposed studies will be carried out by two Ph.D. students supervised by the Austrian (Paul Scheier) and German (Serge Krasnokutski) PIs. Expertise and input of both partners are required to achieve the proposed goals.

• DFG Programme: Research Grants
• International Connection: Austria
• Cooperation Partner: Professor Paul Scheier, Ph.D.