Photoelectron imaging and (2 + 1) resonance enhanced multiphoton ionization spectroscopy study of 2-butanone photoionization dynamics.

(2 + 1) Resonance enhanced multiphoton ionization (REMPI) spectra were recorded for 2-butanone to study its photoionization dynamics. Two-photon excitation (53,200-55,000 cm(-1) and 57,000-59,500 cm(-1)) was used to prepare the molecule in the 3s and 3p Rydberg states, respectively. Vibrational transitions in the spectrum were assigned with the aid of ab initio calculations as well as photoelectron imaging results. Photoelectron imaging data in the 3s Rydberg region exhibits a vibrational progression in the CCOC deformation mode in the ionic state superimposed on an otherwise diagonal (delta v = 0) ionization. Photoelectron imaging data in the 3p Rydberg region shows 3p-3s Rydberg-Rydberg mixing. The ionization energy obtained directly from the 3p photoelectron imaging is 9.541 eV.