Stable isomeric structures of the pyridine cation (C5H5N center dot+) and protonated pyridine (C5H5NH+) elucidated by cold ion infrared spectroscopy

Contains fulltext : 225745.pdf (publisher's version ) (Open Access)8 p

Rap, Nat. Astron.

This dataset contains data for the article "Low-temperature nitrogen-bearing polycyclic aromatic hydrocarbon formation routes validated by infrared spectroscopy". It includes the source data of several figures, i.e. the recorded experimental and calculated IR spectra, and the results of quantum-chemical calculations as log files.Abstract:Polycyclic aromatic hydrocarbons (PAHs) are abundant in many regions of the Universe, representing a major reservoir for cosmiccarbon. However, their formation pathways in cold regions of space remain elusive. Recent astronomical detections showthat current astrochemical models drastically underestimate the abundance of aromatic molecules and suggest that additionalformation pathways such as ion–molecule reactions need to be considered. Here we reveal efficient low-temperature formationpathways towards nitrogen-containing polycyclic aromatic hydrocarbons via exothermic pyridine+ and acetylene ion–moleculereactions. The experimental approach combines kinetics with spectroscopic probing and unambiguously identifies key reactionintermediates and the final nitrogen-containing polycyclic aromatic hydrocarbon product quinolizinium+, a structure that isthought to contribute to the 6.2 μm interstellar emission feature. This study not only provides competing formation pathwaysrelevant in the chemistry of the interstellar medium and Titan's atmosphere, but also delivers information to verify in-silicopotential energy surfaces, astrochemical models and infrared observations

Anharmonicity in the mid-infrared spectra of polycyclic aromatic hydrocarbons: molecular beam spectroscopy and calculations

Contains fulltext : 207494.pdf (publisher's version ) (Open Access

2022 Banhatti et al. PCCP article

This repository contains source data for the Figures in the main article

Far-IR absorption of neutral polycyclic aromatic hydrocarbons (PAHs): light on the mechanism of IR–UV ion dip spectroscopy

Gas-phase IR–UV double-resonance laser spectroscopy is an IR absorption technique that bridges the gap between experimental IR spectroscopy and theory. The IR experiments are used to directly evaluate predicted frequencies and potential energy surfaces as well as to probe the structure of isolated molecules. However, a detailed understanding of the underlying mechanisms is, especially in the far-IR regime, still far from complete, even though this is crucial for properly interpreting the recorded IR absorption spectra. Here, events occurring upon excitation to vibrational levels of polycyclic aromatic hydrocarbons by far-IR radiation from the FELIX free electron laser are followed using resonance-enhanced multiphoton ionization spectroscopy. These studies provide detailed insight into how ladder climbing and anharmonicity influence IR–UV spectroscopy and therefore the resulting IR signatures in the far-IR region. Moreover, the potential energy surfaces of these low-frequency delocalized modes are investigated and shown to have a strong harmonic character.Laboratory astrophysics and astrochemistr

Laboratory astrochemistry of the gas phase: general discussion.

International audienc