MPI spectroscopy in the region of the 3p Rydberg state of some cycloketones

The two-photon resonance three photon ionization spectra of cyclopentanone, cyclohexanone and cycloheptanone in the region of the 3p Rydberg state have been recorded, analysed and compared with the one-photon absorption spectra. A new 3p origin is identified for cyclopentanone. The absence from the MPI spectra of a sharp spectral feature that is observed in the absorption spectra is discussed. Photochemical generation of acetaldehyde is observed at high laser intensities and possible mechanisms for this are considered.