Pulsed photoelectron spectroscopy of negative cluster ions: Isolation of three distinguishable forms of N2O−2

Abstract

Three different ionic species with stoichiometry N2O−2 are generated by varying the neutral precursors in an electron beam ionized free jet expansion. In each case, the ion is isolated by mass spectrometry and then probed using pulsed photoelectron spectroscopy (PES) at 532 and 355 nm (2.330 and 3.495 eV, respectively). The neutral starting materials used in the three preparations are (I) O2 seeded 5% in N2, (II) pure N2O, and (III) NO seeded 10% in Ar. Based on their PES and photofragmentation properties, the three species appear to be best described as (I) O−2 ⋅N2, (II) either O−⋅N2O or more likely a chemically bound species, and (III) NO−⋅NO. It is likely that two of these species are trapped intermediates in the O−+N2O→NO−+NO reaction, suggesting a double minimum potential energy surface. The formation mechanisms of these ions in our source are discussed in the context of previous preparation schemes.