Exchange Report by Oliver Zingsheim

Background information
In my doctoral project within sub-project B3 of the SFB 956, I am studying complex molecules, both stable and transient, of astrophysical interest in the millimeter and submillimeter wavelength regions ─ spectral ranges which are molecule-specific (fingerprint) and allow unambiguous identifications of new species.

Via the SFB 956 student exchange program I visited the research group of Michael C. McCarthy at the Harvard-Smithsonian Center for Astrophysics, Boston, USA in October and November 2016. This group is one of the world leading institutions in the identification and characterization of new molecular species, particularly highly unstable ones of astrophysical interest. McCarthy and co-workers have also been involved in the development of advanced analytical tools, some of them partly in collaboration with our group in Cologne.

Laboratory work
To study highly unstable molecules, they have to be produced in situ in the lab. There a various different techniques to produce them. We used the laser ablation technique. Here, a pulsed laser ablates a metal rod and new molecules can be formed. With a Fourier-transform microwave spectrometer fingerprints can be measured and subsequently analyzed. If these fingerprints, which depend on the structure of the molecule, are measured for different isotopologues of a molecule its bond lengths and angles can be calculated.

McCarthy and coworkers recently discovered that GeC2 has a T-shape. During my visit we pressed a 13C-enriched rod, from germanium, graphite, and amorphous 13C powders, and measured more isotopologues of GeC2 to calculate the structure of it. Further target molecules are aluminum oxides.

For optimal signals, required laser energies and best production procedure of rods have to be found. Here, AlS was chosen as a test molecule. Since its fingerprint can be calculated already, we knew where to look for it. Hence we could optimize the producing conditions. The work performed here on AlS is therefore a crucial step to produce aluminum oxides in the future.

During my stay, not only the laboratory work was exciting, but also the social interaction as well as getting familiar with further high-level research projects at the Harvard campus. The McCarthy-group is worldwide excellent connected and therefore I met for example J. Cernicharo (Madrid) and Paola Caselli (Munich). Further on, at the Harvard Smithsonian Center for Astrophysics I got insights in the work of the Öberg astrochemistry group, the Walsworth group (developing and applying precision measurement tools), the submillimeter receiver lab, the 1.2 meter millimeter-wavelength radio telescope and the HITRAN database. Besides Matthew J. Nava organized a visit at the MIT campus, which is in walking distance, with detailed insights in the labs of the Cummins group.

Personal life
Boston is a really nice city for living, but crazy expensive. I like the combination of the big city, with the skyline consisting of all the skyscrapers, and the close by suburbs where I lived (Cambridge). The daily duty stroke was a beautiful 30 minutes’ walk along the Charles river. All the rowing and sailing boats determine the cityscape. Cambridge is really green with lots of trees and small parks. My favorite one was the Boston public garden (famous location from the movie Good Will Hunting). Watching the famous American sports: baseball, football, ice hockey and basketball in the stadium or in a bar were also highlights during my stay. Some daytrips, like whale watching and hiking in the white mountains, which really deserved their names, are also worth mentioning. Memorable will also be Thanksgiving, which we celebrated at a colleague’s place and the presidential election. Besides I used the time in the US for holidays in Miami and a weekend in New York.

All in all it was areally intense and outstanding time on a scientific as well as personal level and I am really grateful for the SFB 956 to support this trip!