Photoelectron imaging of small silicon cluster anions, Si(n) (-) (n=2-7).

Photoelectron imaging experiments were conducted on small silicon cluster anions, Si(n) (-) (n=2-7), acquired at a photon energy of 3.49 eV (355 nm). Electronic transitions arising from the anion ground states are observed, and the evaluated vertical detachment energies agree well with previous measurements and theoretical calculations. The anisotropy beta parameters have also been determined for each unique feature appearing in the photoelectron angular distributions at the employed photon energy. Separate calculations using density functional theory are also undertaken to determine the relative atomic orbital contributions constructing the interrogated highest occupied and low-lying molecular orbitals of a specific cluster. A method to interpret the observed cluster angular distributions, term the beta-wave approach, is then implemented which provides quantitative predictions of the anisotropy beta parameter for partial wave emission from molecular orbitals partitioned by varying contributions of atomic orbital angular momenta. Highlighted in the beta-wave analysis is the ability of discriminating between disparate molecular orbitals from two nearly isoenergetic structural isomers of opposing point group symmetry for the Si(4) (-) and Si(6) (-) cluster ions, respectively.

Superatom spectroscopy and the electronic state correlation between elements and isoelectronic molecular counterparts.

Detailed in the present investigation are results pertaining to the photoelectron spectroscopy of negatively charged atomic ions and their isoelectronic molecular counterparts. Experiments utilizing the photoelectron imaging technique are performed on the negative ions of the group 10 noble metal block (i.e. Ni-, Pd-, and Pt-) of the periodic table at a photon energy of 2.33 eV (532 nm). The accessible electronic transitions, term energies, and orbital angular momentum components of the bound electronic states in the atom are then compared with photoelectron images collected for isoelectronic early transition metal heterogeneous diatomic molecules, M-X- (M = Ti,Zr,W; X = O or C). A superposition principle connecting the spectroscopy between the atomic and molecular species is observed, wherein the electronic structure of the diatomic is observed to mimic that present in the isoelectronic atom. The molecular ions studied in this work, TiO-, ZrO-, and WC- can then be interpreted as possessing superatomic electronic structures reminiscent of the isoelectronic elements appearing on the periodic table, thereby quantifying the superatom concept.