Mass selective gas phase study of ClO, OClO, ClOO and ClAr by anion-ZEKE-photoelectron spectroscopy

Anion-ZEKE-photoelectron spectra of ClO^- , OClO^- , ClOO^- and the van der Waals cluster ArCl^- have been measured. Refined or new values for the electron affinity of ClO, OClO and ClOO have been found. The peak positions in these spectra are in very good agreement with former ClO^- and OClO^- anion-photoelectron spectra (K. M. Grilles, M. L. Polak and W. C. Lineberger, J. Chem. Phys., 1992, 96, 8012) and a recent ArCl^- anion-ZEKE spectrum (T. Lenzer, I. Yourshaw, M. Furlanetto, G. Reiser and D. Neumark, J. Chem. Phys., 1992, 110, 9578). The higher resolution of our anion-ZEKE-photoelectron spectrum of OClO^- led to a refined assignment of the corresponding anion-photoelectron spectrum. In addition, a strong difference in the relative intensities of the vibrational peaks has been found in the anion-ZEKE- spectrum of OClO^- in comparison with the anion-photoelectron spectrum. For the first time, mass selective spectroscopic information has been obtained for ClOO. The strong similarity to the ArCl^- spectrum indicates a weakly bound van der Waals cluster Cl · O₂ . Binding energies of the anion, neutral ground and neutral excited state could be deduced. These are in good agreement with the electron affinities of Cl and ClOO, but differ from theoretical values (K. A. Peterson and H. J. Werner, J. Chem. Phys., 1992, 96, 8948) by a factor of 4.5 and from thermochemically determined values (J. M. Nicovich, K. D. Kreutter, C. J. Shackelford and P. H. Wine, Chem. Phys. Lett., 1991, 179, 367 and S. Baer, H. Hippler, R. Rahn, M. Siefke, N. Seitzinger and J. Troe, J. Chem. Phys., 1991, 95, 6463) by a factor of 9.