IRMPD spectroscopy of a PAH cation using FELICE: The infrared spectrum and photodissociation of dibenzo[a,l]pyrene

We present the experimental InfraRed Multiple Photon Dissociation (IRMPD) spectrum and fragmentation mass of irregular, cationic PAH dibenzo[a,l]pyrene (C24H14+) in 6–40?m/250–1650 cm?1 range. The use Free-Electron Laser for IntraCavity Experiments (FELICE) enabled us to record its Far-InfraRed (FIR) first time. aim understand how irregularity affects infrared chemistry PAHs. Dibenzo[a,l]pyrene is an asymmetric, non-planar molecule, which all vibrational modes are principle IR-active. Calculated harmonic Density Function Theory (DFT) anharmonic Functional based Tight Binding Molecular Dynamics (DFTB-MD) spectra show a large wealth bands, match experiment well, but with few differences. periphery molecule contains several edge geometries, out possible 11–14?m out-of-plane CH bending region, only one band at 13.5?m prominent. This fact richness CC stretching range make irregular PAHs contributor D-class interstellar spectra. reveal facile 2H-loss no [2C, 2H]-loss, attributed sterically hindered, cove could protect from radiation damage.