The vibrationally resolved spectra of the pyrene cation and doubly-dehydrogenated pyrene cation(C16H10+; Py+ and C16H8+; ddPy+) are presented. Infrared predissociation spectroscopy is employed... Show moreThe vibrationally resolved spectra of the pyrene cation and doubly-dehydrogenated pyrene cation(C16H10+; Py+ and C16H8+; ddPy+) are presented. Infrared predissociation spectroscopy is employed tomeasure the vibrational spectrum of both species using a cryogenically cooled 22-pole ion trap. Thespectrum of Py+ allows a detailed comparison with harmonic and anharmonic density functional theory(DFT) calculated normal mode frequencies. The spectrum of ddPy+ is dominated by absorption featuresfrom two isomers (4,5-ddPy+ and 1,2-ddPy+) with, at most, minor contributions from other isomers.These findings can be extended to explore the release of hydrogen from interstellar PAH species. Ourresults suggest that this process favours the loss of adjacent hydrogen atoms. Show less
