Gas phase studies of astrophysically relevant biomolecules
Final Report Abstract
The purpose of the present project was to study the absorption behavior of astrobiological molecules in the laboratory under conditions encountered in cold astrophysical environments (interstellar medium and molecular clouds). As spectroscopic technique, we chose cavity ring-down laser absorption spectroscopy (CRDS), and the astrophysical conditions were simulated by supersonic jets and cryogenic rare gas matrices. Successful experiments could be carried out in the UV-Vis spectral region for the molecules tryptophan, tryptamine, and tyramine. The infrared wavelength region could not be accessed due to the lack of a properly working OPO. Absorption experiments carried out for adenine and guanine were not successful because the CRDS technique was not as sensitive as resonance-enhanced multiphoton ionization (REMPI) which was used in former investigations. We were also unsuccessful in studying the smallest sugar, glycolaldehyde. Here we were hampered by the problem to produce a molecular beam of monomeric glycolaldehyde. Mass spectra revealed that dimers and even larger clusters were always present. The absorption of clusters could not be observed because the spectra were too broad. On the other hand, we were able to study a series of molecules belonging to another class, the so-called polycyclic aromatic hydrocarbons (PAHs). These molecules have similar properties compared to their biological counterparts: They are provided as crystalline powders, they are difficult to bring into the vapor phase, and they are also of astrophysical relevance. A detailed molecular beam study was carried out for 2,3-benzofluorene. In addition, corannulene and hexabenzocoronene as well as 2- and 9-vinylanthracene were characterized using Ar matrix spectroscopy. For the astrophysical community, these PAH molecules are equally important, as they are discussed as constituents of molecular clouds. Finally, some absorption studies could be performed for linear and cyclic carbon clusters. This latter work is being continued in the frame of a PhD thesis. The absorption spectra of the molecules studied in this project do not match available astrophysical observations. Nevertheless, the present study provides important data which can be compared with forthcoming spectra of higher quality. As far as the future laboratory work is concerned, it will be important to synthesize and characterize larger PAHs which are expected to reveal absorption features in the visible.
Publications
- Laser vaporization of solid samples for absorption spectroscopy of jet-cooled molecules, in Molecules in Space & Laboratory Proceedings, ed. by J. L. Lemaire and F. Combes, NASA ADS, 59.1-59.2 (2007)
Arold, M., Rouillé, G., Huisken, F., Henning, Th.
- UV-VIS absorption spectroscopy of jet-cooled PAHs, in Molecules in Space & Laboratory Proceedings, ed. by J. L. Lemaire and F. Combes, NASA ADS, 57.1-57.4 (2007)
Rouillé, G., Arold, M., Huisken, F., Henning, Th.
- Electronic spectroscopy of biological molecules in supersonic jets: The amino acid tryptophan, AIP Conf. Proc. 1084 (2008) 539-544
Huisken, F., Rouillé, G., Arold, M., Staicu, A., Henning, Th.
- IR, Raman, and UV-Vis spectra of corannulene for use in possible interstellar identification, ChemPhysChem 9 (2008) 2085-2091
Rouillé, G., Jäger, C., Steglich, M., Huisken, F., Henning, Th., Theumer, G., Bauer, J., Knölker, H.-J.
- S1 <-- S0 transition of 2,3-benzofluorene at low temperature in the gas phase, J. Chem. Phys. 129 (2008) 074302
Staicu, A., Rouillé, G., Henning, Th., Huisken, F., Pouladsaz, D., Scholz, R.
- UV-Absorptionsspektroskopie astrophysikalisch relevanter Moleküle im Düsenstrahl, PhD Thesis, Universität Jena, 2009
Arold, M.
