Negative-ion photoelectron spectroscopy of Cu clusters reacted with NO molecules

Abstract

Negative ions of copper clusters reacted with nitric oxide molecules are studied by mass-selected photoelectron spectroscopy. The series of the reacted cluster ions, Cu _n N⁻ Cu _n NO⁻, and Cu _n NO ⁻₂ are observed in the mass spectrum. Photoelectron spectra are obtained at 3.49 eV photon energy for Cu _n N⁻ (n = 2 and 3) and Ca _n NO ⁻₂ (n = 1 and 2). The photoelectron spectrum of Cu₂N⁻ contains a band structure analogous to that of Cu⁻ or Cu ⁻₂ . From the expansion gas pressure dependence of the band peak intensity in the spectrum, it is concluded that Cu₂N⁻ has at least two isomers in the beam. One of the isomers is expected to have a structure in which the central ion is Cu⁻ or Cu ⁻₂ and the residual atom(s) are weakly bound to the ion. For Cu _n NO⁻ (n = 1 − 3), we detected no electron signals with the detachment photon energy of 3.49 eV. The possible structure of CuNO⁻ is discussed in the light of the present results and also on the basis of the recent results of the study of CuO ⁻₂ by Wang and coworkers.