Isomerisation of phenanthrene dication studied by tagging photodissociation ion spectroscopy and DFT calculations

The search for the chemical structures that account diffuse interstellar bands remains main challenge in astrochemistry. It relies on experimental verification of obtained from stable isomers laboratory conditions. actual medium, however, is exposed to much harsher Herein we demonstrate isomerisation small, doubly charged polyaromatic hydrocarbon phenanthrene by electron ionisation at relatively high energies. We performed electronic and vibrational tagging photodissociation spectroscopy measurements. Our results show dication has a broad visible spectrum, making it unsuitable DIB search. also detected another C14H102+ isomer, originating during process. Hole-burning experiments provided IR spectrum an isomer which could be assigned based DFT calculations as fully conjugated system representing global minimum potential energy surface.