We present a study on the structural and electronic properties of the Pt7 cluster by using density functional theory within the generalized gradient approximation for the exchange and correlation. The structures, relative stabilities, and vibrational frequencies of various isomers are calculated and compared with the well-studied Au7 cluster. The ground state of the Pt7 cluster favors a three-dimensional geometrytwo-dimensional local minima are not locatedwhereas for its neighbor, gold heptamer, a two-dimensional geometry is favored. The most stable isomer of Au7 is found to be an edge-capped rhombus structure and an edge-capped tetrahedron structure is found to be the most stable three-dimensional local minimum. The ground state of the Pt7 cluster is found to be a coupled tetragonal pyramid structure with the quintet state in contrast to a pentagonal bipyramid structure obtained by semiempirical molecular dynamics calculation. The natural orbital analysis shows that the overall charge transfer is from 6s to 5d orbitals in the Pt7 cluster, whereas in Au7 cluster it is from 5d to 6s. The molecular orbital picture shows that the bonding orbitals are due to the hybridization between 5d and 6s molecular orbitals in Pt7 cluster, and the nonbonding and antibonding orbitals lie close to the highest occupied molecular orbital. This may be compared with the Au7 electronic structure, where the nonbonding and antibonding orbitals mainly consists of 5d6s hybridized molecular orbitals.

A continuous nitrate free radical (NO3) beam is produced in situ by the pyrolysis of pure gas phase N2O5 at 280 °C (±0.5 °C) in a double-heater inlet system on a double-chamber UPS Machine-II which was built specifically to detect transient species. The HeI photoelectron spectroscopy (PES) of the NO3 radical is recorded for the first time. Five obvious bands emerge on the PE spectrum of the NO3 radical. A very sharp peak with the lowest ionization energy at 12.55±0.01 eV originates from electron ionization of the HOMO for the NO3 radical, corresponding to the NO3+(1A1′)←NO3(2A2′) transition. To assign the bands of the PE spectrum of the NO3 radical, the improved density functional theory (DFT) calculation based on the Amsterdam density functional (ADF) program package has been carried out according to D3h symmetry for the neutral ground state of the NO3 radical and the equilibrium geometries of several ionic states of the cationic species. The ionization energies computed are in reasonable agreement with the PES experimental ionization energies. Both PES experimental and DFT calculation provide evidence on the lowest triplet and singlet states of the NO3+ cation.

Ultraviolet photoelectron spectra of 17 substituted silatranes (silatrane = 2,8,9-trioxa-5-aza-1silabicyclo[3.3.3] undecane), measured for gas-phase samples at convenient temperatures, are presented. The spectra are interpreted using both valence-electron molecular orbital calculations and a composite-molecule model. The first ionization band is, in most cases, assigned to the nitrogen lone-pair electrons which comprise the S i c N dative bond. This assignment is verified by the observed sensitivity of the location of this band towards substitution at the silicon atom. The oSIN ionization energies also correlate with the N 1 s binding energies measured for these compounds.

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