Testing the photostability of 1-Cyanonaphthalene-(H2O)1,2 complexes to predict their resistance to the interstellar radiation field

The studies of spectroscopy, reactivity, and photochemistry of CN-substituted aromatic molecules have acquired particular relevance since their detection in TMC-1 in 2018. In this context, the REMPI spectroscopy of 1-cyanonaphthalene (1CNN) and its complexes with one (1CNN-W) and two (1CNN-W 2 ) water molecules (W = H 2 O) was recorded and compared with theoretical calculations at the CAM-B3LYP/aug-cc-pVDZ level, validating the theoretical method and justifying its use in predicting some properties of the cat ionic species in their ground and excited electronic states. The adiabatic ionization potential (IP ad ) for 1CNN monomer was experimentally determined for the first time (8.432 eV) and agrees to well within 1% with the theoretical value (8.417 eV). Ionization thresholds for 1CNN-W and 1CNN-W 2 complexes, as well as the water evaporation threshold in the cationic state of the latter complex, were also determined experimentally and were found to agree with the theoretical results to within 1% . Based on the available data, it is tentatively predicted that once 1CNN forms aggregates with ≥1 H 2 O molecules, these complexes will be ionized by Ly-α irradiation, but they will be stable in their cationic state. • 1st experimental determination of 1Cyanonaphthalene adiabatic ionization potential. • Ionization thresholds for 1Cyanonaphthalene-water complexes are reported. • Evaporation threshold in the cationic state of the 1:2 complex was determined. • It is predicted that 1CNN-H 2 O n will be stable in their cationic state under Ly-α.