10min:

C. P. ENDRES, V. LUTTER, J. KÖTTING, J. KRIEG, S. THORWIRTH, S. SCHLEMMER, T. F. GIESEN, I. Physikali\-sches Institut, Universität zu Köln, 50937 Köln, Germany; M. E. HARDING, Karlsruher Institut für Technologie, Institut für Nanotechnologie, 76021 Karlsruhe, Germany; J. VÁZQUEZ, Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA.

Linear C₃ is a floppy molecule which possesses an extremely low lying bending mode, ₂, at roughly 60 cm^-1 or 1.9 THz. Based on highly accurate laboratory data^,, C₃ has been detected in various astronomical sources^, most recently with the HIFI instrument aboard the Herschel satellite. Although C₃ turns out to be quite abundant in interstellar environments which makes a search for ¹³C substituted isotopologs feasible, other isotopologs could not be detected so far, because no accurate transition frequencies have been available for these species in this frequency range. Relative abundance ratios of C₃ isotopologs might give important hints on its building mechanism and further constraints for chemical networks.

In this work, the spectrum of the ₂ lowest bending mode of ¹³CCC has been investigated. We used laser ablation of ¹³C enriched carbon samples to record absorption spectra in a supersonic jet expansion. The radiation in our setup is generated by a synthesizer referenced to a Rubidium standard in combination with a frequency multiplier chain and detected by a liquid Helium cooled InSb bolometer. The laboratory search has been supported by high-level coupled-cluster calculations, which turns out to compare very favorably with obtained experimental molecular parameters.