Laboratory rotational spectroscopy and astronomical search of ethynyl substituted naphthalene

TL;DR

This study reports the laboratory rotational spectra of ethynyl naphthalene derivatives to aid astronomical detection efforts, providing spectroscopic data and upper abundance limits in TMC-1.

Contribution

First laboratory measurement of the rotational spectra of 1- and 2-ethynylnaphthalene, enabling future astronomical searches for these molecules.

Findings

Spectroscopic parameters for ethynyl naphthalene derivatives were accurately determined.

No definitive detection of these species in TMC-1, but upper abundance limits were established.

Data supports future interstellar molecular identification efforts.

Abstract

The recent interstellar detection of cyanonaphthalenes bring interest in related aromatic molecular species that could be present in similar astronomical environments. In this context, ethynyl derivatives of naphthalene are promising candidates to be observed in the Taurus Molecular Cloud (TMC-1), where cyanonaphthalenes together with cyano- and ethynyl- derivatives of cyclopentadiene and benzene have been detected. To enable the interstellar searches for ethynyl derivatives of naphthalene, their pure rotational spectra need to be investigated in the laboratory. We have observed for the first time the rotational spectra of 1- and 2-ethynylnaphthalene species using a broadband Fourier-transform microwave spectrometer operating in the 2-8 GHz frequency region. Accurate spectroscopic parameters are derived from the analysis of the experimental spectra, allowing for reliable predictions for astronomical searches. Our searches in TMC-1 for both isomers provide upper limits for the abundances of these species.