Ion core structure in (N2O)n+(n=2–8) studied by infrared photodissociation spectroscopy

IR photodissociation (IRPD) spectra of (N(2)O)(2)(+) x Ar and (N(2)O)(n)(+) with n=3-8 are measured in the 1000-2300 cm(-1) region. The (N(2)O)(2)(+) x Ar ion shows an IRPD band at 1154 cm(-1), which can be assigned to the out-of-phase combination of the nu(1) vibrations of the N(2)O components in the N(4)O(2)(+) ion; the positive charge is delocalized over the two N(2)O molecules. The geometry optimization and the vibrational analysis at the B3LYP/6-311+G(*) level show that the N(4)O(2)(+) ion has a C(2h) structure with the oxygen ends of the N(2)O components bonded to each other. The IRPD spectra of the (N(2)O)(n)(+) (n=3-8) ions show three prominent bands at approximately 1170, approximately 1275, and approximately 2235 cm(-1). The intensity of the approximately 1170 cm(-1) band relative to that of the other bands decreases with increasing the cluster size. Therefore, the approximately 1170 cm(-1) band is ascribed to the N(4)O(2)(+) dimer ion core and the approximately 1275 and approximately 2235 cm(-1) bands are assigned to the nu(1) and nu(3) vibrations of solvent N(2)O molecules, respectively. Since the band of the N(4)O(2)(+) ion core is located at almost the same position for all the (N(2)O)(n)(+) (n=2-8) clusters, the C(2h) structure of the dimer ion core does not change so largely by the solvation of N(2)O molecules, which is quite contrastive to the isoelectronic (CO(2))(n)(+) case.