DISCOVERY OF 13CCC in SgrB2(M)

Small carbon chain molecules like linear C$_3$ are thought to play a crucial role in the formation of larger, complex molecules, including pre-biotic species. The formation pathways of organic molecules with carbon chains as backbones is by far not well understood. Studies of isotope fractionation have proven to be a useful tool of tracing chemical reaction pathways and to elucidate formation and destruction processes of interstellar molecules. Recent velocity-resolved observations in the far-infrared have resulted in the detection of C$_3$ ro-vibrational transitions in the warm envelopes of star-forming hot cores W31C, W49N and DR21(OH). Multiple far-infrared transitions of C$_3$ have also been detected towards the Galactic center molecular clouds SgrB2(M) and Sgr B2(N). Since C$^+$ is involved in an important step of the formation route of the C$_3$ molecule, it is likely that effects of isotopic fractionation of C$^+$ will manifest itself in the $^{12}$C$_3$/$^{13}$CCC and $^{12}$C$_3$/C$^{13}$CC ratios as well._x000d_ Based on high resolution THz- laboratory measurements of C$_3$ and its $^{13}$C-isotopologues conducted at the Kassel laboratories, we used the GREAT-receiver onboard SOFIA for a first ever detection of $^{13}$CCC towards SgrB2(M). In this talk we present results and possible implications of the observation. _x000d