Unveiling reaction mechanisms by isomer-selective detection of reactive intermediates requires advanced spectroscopic knowledge. We study the photoionization of fulvenone (c-C5H4=C=O), a reactive ketene species relevant in catalytic pyrolysis of lignin, which was generated by pyrolysis of 2-methoxy acetophenone. The high-resolution threshold photoelectron spectrum (TPES) with vacuum ultraviolet synchrotron radiation revealed well-resolved vibrational transitions, assigned to ring deformation modes of the cyclopentadiene moiety. The adiabatic ionization energy was determined to be 8.25±0.01 eV and is assigned to the (Formula presented.) 2A2← (Formula presented.) 1A1 transition. A broad and featureless band arising at 9 eV is associated with the (Formula presented.) 2B1← (Formula presented.) 1A1 excitation. A conical intersection is responsible for the ultrafast relaxation of the fulvenone cation from the (Formula presented.) into the (Formula presented.) state resulting in a featureless and lifetime broadened band. These insights will increase the detection capabilities for fulvenone and thereby help to elucidate reaction mechanisms in lignin catalytic pyrolysis.
- photoelectron spectroscopy
- reactive intermediates
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Physical and Theoretical Chemistry