Astronomical detection of the cyanobutadiynyl radical C5N

TL;DR

This paper reports the astronomical detection of the elusive C5N radical in a dark cloud and tentatively in a circumstellar envelope, revealing discrepancies with existing chemical models and providing new insights into interstellar chemistry.

Contribution

First detection of C5N in space, highlighting its lower abundance than predicted and comparing it with related molecules in different environments.

Findings

C5N detected in TMC1 and tentatively in IRC+10216

C5N is two orders of magnitude less abundant than HC5N

Detected C3H radical in excited state in IRC+10216

Abstract

We report the detection of the elusive carbon-chain radical C5N in the dark cloud TMC1 and its tentative detection in the circumstellar envelope IRC+10216. C5N appears to be two orders of magnitude less abundant than the related molecule HC5N and much less abundant than expected from current gas phase chemistry models. In comparison the HC3N to C3N abundance ratio is of the order of 10, in reasonable agreement with model predictions. We have also detected in IRC+10216 two lines arising from the C3H radical in its excited nu_4=1 state.