Multiphoton ionization and dissociation of

We investigate multiphoton ionization (MPI) of at 532 nm excitation wavelength in an intensity range of -. We find strong fragmentation of the molecule with formation of , , , and as charged dissociation products. Photoelectron spectra show that the charged products originate in photodissociation of . Ionic dissociation starts after excitation of to the state and probably high vibrational levels of the bending mode in . Symmetric is significantly less probable than asymmetric dissociation. MPI of mainly populates ionic X (000) and (100) vibronic states below light intensity. At high intensity also B vibronic states seem to become directly populated with rising probability. All lowest-order MPI electron groups are accompanied by at least one above-threshold ionization group. A sensitive dependence of the photoelectron spectra on light intensity may point to bond-angle softening of low-lying X vibronic states of which is expected to be brought about by a favourable resonant one-photon coupling between the X and à electronic states.