NEGATIVE ION PHOTOELECTRON SPECTROSCOPY OF: $NO^{-}(Ar)_{1}, NO^{-}(Kr)_{1}, NO^{-}(Xe)_{1}$, AND $N_{2}O_{2}$
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Date
1987
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Ohio State University
Abstract
We have recorded the photoelectrom (photodetachment) spectra of the gasphase negative ions: $NO^{-}(Ar)_{1}, NO^{-}(Kr)_{1}$, and $NO-(Xe)_{1}$ using 2.409 eV photons, and of $N_{2}O_{2}^{-}$ using both 2.540 eV and 2.707 eV photons. All of these ions were generated in a supersonic expansion ion source with various mixtures of nitric oxide and rare gases. All of the rare gas negative cluster ion spectra exhibit structured spectral patterns which strongly resemble that obtained for free $NO^{-}$, but which are shifted to lower electron energies with their individual peaks broadened. Each of these spectra is interpreted in terms of a largely intact $NO^{-}$ sub-ion which is solvated and stabilized by its rare gas solvent atom. The ion-solvent dissociation energy for a given $NO-(Rg)_{1}$ cluster ion dissociating into $NO^{-}$ and Rg is given by the energy difference between the origin peak of the free $NO^{-}$ spectrum and the origin peak of a given $NO^{-}(Rg)_{1}$ spectrum. The values of these shifts were found to be: $0.058\pm 0.011 eV, 0.099\pm 0.018 eV, 0.161\pm 0.024 eV$ for the argon, krypton, and xenon complexes, respectively. Values for the electron affinities of these complexes were found to be: 0.095 eV, 0.136 eV, and 0.204 eV for the argon, krypton, and xenon complexes, respectively. Both of our photoelectron spectra for $N_{2}O_{2}^{-}$ came at the low electron energy end of our spectral range. The electron affinity of the $N_{2}O_{2}$ species studied here can be given a lower bound of 2.1 eV. Studies by $Johnson^{1}$ at higher photon energies indicate the existence of other isomers as well.
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$^{1}$ M. A. Johnson (private communication)
Author Institution: Westinghouse R \& D Center; Dept. of Chemistry, The Johns Hopkins University
Author Institution: Westinghouse R \& D Center; Dept. of Chemistry, The Johns Hopkins University