Rotational spectra of interstellar N- and CN-PAHs: pyrene and coronene

Abstract

The detection of benzonitrile (C6H5CN), 1- and 2-cyano-naphthalene (C10H7CN) in the cold, dark molecular cloud TMC-1 at centimetre (cm) wavelengths has opened up prospects for the detection of other N- and CN-containing polycyclic aromatic hydrocarbons (PAHs). In this light, the pure rotational spectra of N-pyrene (C15H9N), CN-pyrene (C15H9CN), N-coronene (C23H11N) and CN-coronene (C23H11CN) are reported here for the first time. The B3LYP/6-311+G(d,p) level of theory, in the Density Functional Theory (DFT) calculations, achieves the best performance for calculating the spectroscopic parameters and simulating the rotational spectra. The large permanent dipole moment of CN-PAHs makes them the most suitable PAH species for detection in the interstellar medium. Additionally, pyrene's smaller partition function makes CN-pyrene a prime candidate to be discovered in cold, dark molecular clouds such as the TMC-1. The present work sets a benchmark for theoretical rotational spectra of N- and CN-containing PAHs and may act as a guide for laboratory experiments and observational searches.

References in corpus (18)

• The Mid-Infrared Spectrum of Star-Forming Galaxies: Global Properties of PAH Emission
• The rich 6 to 9 um spectrum of interstellar PAHs
• Detection of the Aromatic Molecule Benzonitrile ($c$-C${}_6$H${}_5$CN) in the Interstellar Medium
• Detection of Two Interstellar Polycyclic Aromatic Hydrocarbons via Spectral Matched Filtering
• The CH out-of-plane bending modes of PAH molecules in astrophysical environments
• An Anomalous Component of Galactic Emission
• The aromatic infrared bands as seen by ISO-SWS: probing the PAH model
• The Infrared Spectra of Very Large Irregular Polycyclic Aromatic Hydrocarbons (PAHs): Observational Probes of Astronomical PAH Geometry, Size and Charge
• The unusual hydrocarbon emission from the early carbon star HD 100764: The connection between aromatics and aliphatics
• Early Science from GOTHAM: Project Overview, Methods, and the Detection of Interstellar Propargyl Cyanide (HCCCH${}_2$CN) in TMC-1
• Direct spectroscopic evidence for ionized PAHs in the interstellar medium
• Calibration and Systematic Error Analysis For the COBE-DMR Four-Year Sky Maps
• Search for corannulene (C20H10) in the Red Rectangle
• PAH Spectroscopy from 1-5 $\mu$m
• Polycyclic Aromatic Hydrocarbons, the Anomalous Microwave Emission, and Their Connection to the Cold Neutral Medium
• Rotational spectroscopy of interstellar PAHs
• Theoretical study of infrared spectra of interstellar PAH molecules with N, NH & NH${}_2$ incorporation
• Search for PAHs in the Perseus molecular cloud with the Green Bank Telescope

Cited by in corpus (3)

• The High-Resolution Far- to Near-Infrared Anharmonic Absorption Spectra of Cyano-Substituted Polycyclic Aromatic Hydrocarbons from 300-6200 cm${}^{-1}$
• A comprehensive rotational study of astronomical iso-pentane within 84 to 111 GHz
• Research on the Interstellar Medium and Star Formation in the Galaxy: An Indian Perspective