Detection of ethynylbenzene in TMC-1 and the interstellar search for 1,2-diethynylbenzene

Abstract

Aims. We investigate the outcome of an electrical discharge of naphthalene and search for the resulting products in the Taurus Molecular Cloud (TMC-1). Methods. Using chirped pulse Fourier transform microwave spectroscopy paired with an electric discharge source, we investigated products resulting from the naphthalene discharge. Quantum chemical calculations were used to help assign species and investigate potential reaction pathways relevant to the interstellar medium. These products were searched for in TMC-1 using the QUIJOTE line survey, covering 31.0-50.3 GHz. Results. We confirm the detection of ethynylbenzene in TMC-1, and we also present a new molecular species, 1,2-diethynylbenzene, which could play an important role in the formation of naphthalene. Over ten products have been identified as resulting from the discharge, with only one of these species found in a previous IR-UV discharge study of naphthalene. Conclusions. Ethynylbenzene has definitively been detected in TMC-1, and while we have identified a potentially important species for the formation of naphthalene and an exothermic reaction pathway, there is no current indication of its presence in TMC-1.