| Abstract : | Since the discovery of benzonitrile (C6H5CN), 1- and 2-cyanonaphthalene (C10H7CN) in the cold, dark molecular cloud TMC-1, the search for other N- and CN-containing polycyclic aromatic hydrocarbon (PAH) molecules have gained importance. The present work investigates the pure rotational spectra of two astronomically-relevant PAHs; pyrene (C16H10) and coronene (C24H12) in N- and CN-substituted PAH forms (C15H9N, C16H9CN, C23H11N and C24H11CN) in the frequency range of 8 to 33 GHz. Density Functional Theory with anharmonic vibrational frequency calculations has been employed for calculating the spectroscopic parameters and simulating the rotational spectra. The accuracy of the computational methods adopted in this work has been verified before applying them to the chosen molecules. Results found CN-PAHs the more suitable candidates to be detected in the interstellar medium due to their larger permanent dipole moment. It is observed that pyrene shows a smaller partition function that makes CN-pyrene a strong 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. |
