Threshold effects in I- CH₃ CN and I- H₂ O cluster anion detachment: The angular distribution as an indicator of electronic autodetachment

I- H₂ O and I- CH₃ CN cluster anion photodetachment properties (photoelectron spectra and angular distributions) are recorded via velocity mapped photoelectron imaging for wavelengths between 270 and 340 nm, in small energy increments. These are compared with free I- detachment results and reveal the presence of a sharp change in the angular distribution for the P2 3/2 spin orbit channel in the vicinity of the P2 1/2 threshold. The effect is seen at this threshold in the I- H₂ O cluster anion and just below threshold for I- CH₃ CN. The effect is attributed to an electronic autodetachment process, which is dependent on electronic energy transfer mediated by the electron-neutral complex produced in the excitation process. These results highlight the potential of cluster anion detachment as a probe of electron-molecule interactions and in particular the sensitivity of the angular distributions to intracluster electron transfer processes.