Photoelectron spectroscopy of clustered transition state precursors IHI−·Ar and BrHI−·Ar

Photoelectron (PE) spectra of the IHI−·Ar and BrHI−·Ar clusters were measured in order to probe the effect of clustering on the transition state spectroscopy of the X+HI→XH+I (X=I, Br) reactions. Addition of one argon atom to XHI− leads to a shift of the IHI− and BrHI− spectra to lower electron kinetic energies by 18 and 36 meV, respectively. It also significantly reduces the contribution of vibrational hot bands to the photoelectron spectra. The IHI−·Ar spectrum shows a new progression corresponding to hindered IHI rotor states near the I+HI (ν=1) threshold.