Infrared spectroscopy of O˙⁻ and OH⁻ in water clusters: evidence for fast interconversion between O˙⁻ and OH˙OH⁻

Abstract

We present infrared multiple photon dissociation (IRMPD) spectra of (H₂O)_nO˙^- and (H₂O)_nOH^- cluster ensembles for n[combining macron] ≈ 8 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 H₂OO˙^- and H₂OOH^- interactions span almost the whole spectral region of interest. Experimentally, evaporation of OH˙ is observed to a small extent, which requires interconversion of (H₂O)_nO˙^- into (H₂O)_n-1OH˙OH^-, with subsequent H₂O evaporation preferred over OH˙ evaporation. The modeling shows that (H₂O)_nO˙^- and (H₂O)_n-1OH˙OH^- cannot be distinguished by IRMPD spectroscopy.