Studies on the multiphoton ionization spectrum of the jet-cooled acetyl radical at 6.2–7.6 eV Original Research Article

Acetyl radical was produced in a molecular beam by pyrolysis of acetone with a flash pyrolysis nozzle and was cooled by supersonic expansion. A continuous multiphoton ionization (MPI) spectrum of the jet-cooled acetyl radical at 6.2–7.6 eV was first observed in the experiment. The spectrum from 6.2 eV to ionization threshold has resulted from 2+1 resonance-enhanced MPI (REMPI) through its high-lying electronic states. These states are shown to be dissociative and metastable. The adiabatic ionization potential of the acetyl radical was redetermined to be 7.01±0.02 eV from the derivative of MPI spectrum near ionization threshold directly. This work demonstrates that MPI technique can be easily used to monitor the produced acetyl radical in molecular beams.