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Photoelectron (PE) spectra have been collected for the clustered bihalide anions XHX−∙(M) (X=Br, I) and BrHI−∙(M), where M=H2O, HBr, and HI, in order to probe the effects of strongly solvating species on the PE spectra of transition state precursor anions. The PE spectra of the XHX−∙(H2O) ions show similar vibrational progressions as the spectra of the bare BrHBr− and IHI− anions, indicating that photodetachment of the bare and hydrated ions accesses similar XHX transition state geometries on the X+HX reactionpotential energy surfaces. These results are consistent with electronic structure calculations that predict a double hydrogen-bonded XHX−∙(H2O) structure in which the symmetry of the strong XHX−hydrogen bond is largely preserved. In contrast, PE spectra of BrHBr−(HBr)1,2 and IHI−(HI)1,2 indicate that the addition of a single HBr or HI disrupts the symmetric XHX− bond, resulting in structures of the form X−∙(HX)n, and altering the geometry of the Franck–Condon region accessed on the neutral potential energy surfaces. Similarly, PE spectra of BrHI−∙(HI) and BrHI−∙(HBr) suggest anion structures of the form I−∙(HBr)HI and I−∙(HBr)2, respectively.


Copyright 2003 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

The following article appeared in Gómez, Harry; Meloni, Giovanni; Madrid, James; Neumark, Daniel M. Anion Photoelectron Spectroscopy of Solvated Transition State Precursors. Journal of Chemical Physics. 7/8/2003, Vol. 119 Issue 2, p872. and may be found at



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