Infrared spectroscopy of O(•−) and OH(−) in water clusters: evidence for fast interconversion between O(•−) and OH(•)OH(−)†

We present infrared multiple photon dissociation (IRMPD) spectra of (H(2)O)(n)O(•−) and (H(2)O)(n)OH(−) cluster ensembles for [Formula: see text] and 47 in the range of 2400–4000 cm(−1). Both hydrated ions exhibit the same spectral features, in good agreement with theoretical calculations. Decomposition of the calculated spectra shows that bands originating from H(2)O⋅⋅⋅O(•−) and H(2)O⋅⋅⋅OH(−) interactions span almost the whole spectral region of interest. Experimentally, evaporation of OH(•) is observed to a small extent, which requires interconversion of (H(2)O)(n)O(•−) into (H(2)O)(n–1)OH(•)OH(−), with subsequent H(2)O evaporation preferred over OH(•) evaporation. The modeling shows that (H(2)O)(n)O(•−) and (H(2)O)(n–1)OH•OH(−) cannot be distinguished by IRMPD spectroscopy.