Visible photodissociation spectroscopy of PAH cations and derivatives in the PIRENEA experiment

TL;DR

This study measures gas-phase electronic spectra of PAH cations and derivatives using multiphoton dissociation spectroscopy in the 430-480 nm range, providing new insights into their spectral properties and absorption cross-sections.

Contribution

It presents the first gas-phase spectra of dehydrogenated PAH cations and combines experimental data with theoretical calculations for detailed analysis.

Findings

Spectra obtained for pyrene, methylpyrene, coronene, and its dehydrogenated derivative.

First gas-phase spectra of highly reactive dehydrogenated PAH cations.

Estimated absorption cross-sections using kinetic Monte Carlo simulations.

Abstract

The electronic spectra of gas-phase cationic polycyclic aromatic hydrocarbons (PAHs), trapped in the Fourier Transform Ion Cyclotron Resonance cell of the PIRENEA experiment, have been measured by multiphoton dissociation spectroscopy in the 430-480 nm spectral range using the radiation of a mid-band optical parametric oscillator laser. We present here the spectra recorded for different species of increasing size, namely the pyrene cation (C16H10+), the 1-methylpyrene cation (CH3-C16H9+), the coronene cation (C24H12+), and its dehydrogenated derivative C24H10+. The experimental results are interpreted with the help of time-dependent density functional theory calculations and analysed using spectral information on the same species obtained from matrix isolation spectroscopy data. A kinetic Monte Carlo code has also been used, in the case of pyrene and coronene cations, to estimate the absorption cross-sections of the measured electronic transitions. Gas-phase spectra of highly reactive species such as dehydrogenated PAH cations are reported for the first time.