Fragmentation pathways of diphenyl ether radical cations

The fragmentation pattern of diphenyl ether (DPE) for both non-resonant and resonant multiphotoionization conditions was obtained. The competition between the processes leading to mass-to-charge ratios m/z 142 and m/z 77 was analyzed. The appearance energies, obtained in this work for the rearrangement and cleavage fragmentation channels, are found to be in relative agreement with the generally accepted values of 12.69 eV and 14.88 eV, respectively. In fact, the agreement is only obtained for values of the ionization energy (IE) somewhat higher than the NIST reference value. The lack of a reliable IE value hinders the possibility to better pinpoint the appearance energies for all channels involved. From these studies we may say that, with the intensities and duration of the laser pulses used, the ladder switching mechanism does not always apply.