STRUCTURE AND SPECTROSCOPY OF MOLECULES OF ASTROCHEMICAL INTEREST AND THEIR AGGREGATES WITH WATER

ANA NIEDOJADLO; ALEJANDRO GUTIÉRREZ-QUINTANILLA; GUSTAVO PINO; JENNIFER NOBLE

Traverse city

Simposio; 2023 Kavli-IAU Astrochemistry Symposium. Astrochemistry VIII - From the First Galaxies to the Formation of Habitable Worlds.; 2023

International Astronomical Union

Introduction: The first detection of an aromatic molecule in space was made in 2001, when benzene was identified in a protoplanetary nebula.[1] More recently, in 2018, the benzonitrile molecule was the first nitrogenous aromatic cycle detected in the interstellar medium (ISM).[2] This finding was largely due to advances in detection through the use of radio telescopes and to the strong dipole moment given by the cyano group. In early 2021, the detection of 1- and 2-cyanonaphthalene was reported.[3] These findings confirm that nitrogenous polycyclic aromatic hydrocarbons (NPAHs) are a component of the interstellar aromatic inventory. Both in the ISM and in different astronomical environments, NPAHs can form aggregates with small molecules such as water, which alters their spectroscopy and their photophysical and photochemical properties. Therefore, the laboratory study of the spectroscopy, photochemistry and photophysics of this type of NPAH and their aggregates with H2O is of great interest in understanding and predicting the chemical composition of the ISM. In this context, we present a study of the spectroscopy of 1-cyanonaphthalene (1CNN) and its aggregates with 1 and 2 molecules of H2O in the gas phase under conditions of low pressure and temperature to simulate those of the ISM.Results and conclusions: The generation of 1CNN and its aggregates with 1 and 2 H2O molecules was carried out by supersonic expansion in a vacuum chamber, reaching pressures and temperatures of the order of 10-6 mbar and 30 K, respectively. The REMPI spectrum (1+1') was recorded in the 225-325 nm range, with shifts to lower energies observed for the case of the aggregates with respect to the spectrum of the 1CNN monomer, and signs of evaporation of a water molecule in the case of 1CNN:2H2O. The ionization energy of the aggregates was determined: 1CNN:H2O (8.46 eV) and 1CNN:2H2O (8.40 eV). The experimental results showed good agreement with electronic structure calculations at the CAM-B3LYP/aug-cc-pvdz-D3 level.The small decrease observed in the ionization energy with the degree of solvation indicates that the effect of the water molecule is similar in the neutral and ionic states of 1CNN. References1)Cernicharo, J., et al. ApJ., 2001, 546.2, L123.2)McGuire, B. A., et al. Sci., 2018, 359.6372, 202-205.3)McGuire, B. A., et al. Sci., 2021, 371.6535, 1265-1269.