Photoelectron imaging study of vibrationally mediated electron autodetachment in the type I isomer of the water hexamer anion

We exploit the high collection efficiency of negative ion photoelectron imaging for low energy electrons to monitor the energy and angular distributions of the photoelectrons arising from vibrational excitation of the water hexamer anion in the vicinity of the OH stretching fundamentals. Photoelectrons from the low electron binding energy isomer (type II) appear as a smoothly varying outer ring with the anisotropic angular distribution expected for direct photodetachment. The higher binding isomer (type I) yields very slow electrons that are strongly modulated through the OH stretching resonances, which are discussed in the context of a statistical (IVR-based) ejection mechanism.