Infrared Spectra of Solid HCN Embedded in Various Molecular Environments for Comparison with the Data Obtained with JWST

Abstract

Hydrogen cyanide (HCN) molecules serve as an important tracer for the chemical evolution of elemental nitrogen in the regions of star and planet formation. This is largely explained by the fact that N atoms and N _2 molecules are poorly accessible for observation in the radio and infrared (IR) ranges. In turn, gas-phase HCN can be observed at various stages of star formation, including disks around young stars, cometary comas, and atmospheres of the planetary satellites. Despite the large geography of gas-phase observations, an identification of interstellar HCN ice is still lacking. In this work we present a series of IR spectroscopic measurements performed at the new ultrahigh vacuum cryogenic apparatus aiming to facilitate the search for interstellar HCN ice. A series of high-resolution laboratory IR spectra of HCN molecules embedded in the H _2 O, H _2 O:NH _3 , CO, CO _2 , and CH _3 OH ices at 10 K temperature is obtained. These interstellar ice analogues aim to simulate the surroundings of HCN molecules by the main constituents of the icy mantles on the surface of the interstellar grains. In addition, the spectra of HCN molecules embedded in the solid C _6 H _6 , C _5 H _5 N, and C _6 H _5 NH _2 are obtained to somehow simulate the interaction of HCN molecules with carbonaceous material of the grains rich in polycyclic aromatic hydrocarbons. The acquired laboratory spectroscopic data are compared with the publicly available results of NIRSpec James Webb Space Telescope observations toward quiescent molecular clouds performed by the IceAge team.

Keywords

• Laboratory astrophysics
• Ice spectroscopy
• Interstellar clouds
• Astrochemistry
• Interstellar molecules
• Star forming regions