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

Negative ions of copper clusters reacted with nitric oxide molecules are studied by mass-selected photoelectron spectroscopy. The series of the reacted cluster ions, CunN-, CunNO-, and CunNO2- are observed in the mass spectrum. Photoelectron spectra are obtained at 3.49 eV photon energy for CunN- (n = 2 and 3) and CunNO2- (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 CunNO- (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 CuO2- by Wang and coworkers.