OBSERVATION OF PHOTO-DOUBLE IONIZATION OF CARBON-MONOXIDE BELOW THE ADIABATIC DOUBLE-IONIZATION POTENTIAL BY THRESHOLD-PHOTOELECTRON-PHOTOELECTRON COINCIDENCE SPECTROSCOPY

The production of C+ and O+ ion pairs in carbon monoxide at photon ene rgies below the adiabatic double-ionization threshold of 41.25 eV has been probed in a threshold photoelectron-photoelectron coincidence (TP EPECO) experiment using tunable VUV radiation and a sensitive electron spectrometer. The TPEPECO spectra provide evidence of C+ + O+ product ion that does not involve creation and dissociation of a molecular dic ation, but instead results from complete dissociation of a molecular c ation followed by autoionization of the atomic oxygen fragment. Furthe rmore, an electron-electron coincidence signal has been detected at ph oton energies as low as 36.5 eV, well below the previously measured on set for C+ + O+ production.