Highest weight irreducible representations favored by nuclear forces within SU(3)-symmetric fermionic systems

The consequences of the attractive, short-range nucleon-nucleon (NN) interaction on the wave functions of nuclear models bearing the SU(3) symmetry are reviewed. The NN interaction favors the most symmetric spatial SU(3) irreducible representation (irrep), which corresponds to the maximal spatial overlap among the fermions. The consideration of the highest weight (hw) irreps in nuclei and in alkali metal clusters, leads to the prediction of a prolate to oblate shape transition beyond the mid–shell region. Subsequently, the consequences of the use of the hw irreps on the binding energies and two-neutron separation energies in the rare earth region are discussed within the proxy-SU(3) scheme, by considering a very simple Hamiltonian, containing only thethree dimensional (3D) isotropic harmonic oscillator (HO) term and the quadrupole-quadrupole interaction. This Hamiltonian conserves the SU(3) symmetry and treats the nucleus as a rigid rotator.

Cyclic(Alkyl)(Amino) Carbene-Assisted Reduction of Carbon Dioxide: Isolation of Crystalline Alkali Metal Clusters of Supported CO2 Radical Anions and Dianions

The reduction of the relatively inert carbon–oxygen bonds of CO₂to access useful CO₂-derived organic products is one of the most important fundamental challenges in synthetic chemistry. Achieving this reduction using earth-abundant main group elements (MGEs) is especially arduous because of the difficulty in achieving strong inner-sphere reactions and bond activation events between CO₂and the MGE. Herein we report the first successful chemical reduction of a zwitterionic carbene-CO₂adduct by either one or two equivalents of light alkali metals to form isolable, room-temperature-stable crystalline clusters exhibiting remarkably diverse electronic and structural characteristics. The reduction of a CAAC-CO₂adduct [CAAC–CO₂, <b>1</b>, CAAC = cyclic (alkyl)(amino) carbene] with one equivalent of lithium, sodium or potassium metal yields the monoanionic radicals (THF)₃Li₂(CAAC–CO₂)₂(<b>2</b>), (THF)₄Na₄(CAAC–CO₂)₄(<b>3</b>), or (THF)₄K₄(CAAC–CO₂)₄(<b>4</b>). The reduction of <b>1</b>by two or more equivalents of lithium, sodium, or potassium yields the open-shell, dianionic clusters (THF)₂Li₆(CAAC–CO₂)₃(<b>5</b>), Li₁₂(CAAC–CO₂)₆(<b>6</b>), Na₁₂(CAAC–CO₂)₆(<b>7</b>), and K₁₀(CAAC–CO₂)₅(<b>8</b>). Each of the clusters was studied by a combination of X-ray crystallography, FTIR, UV-Vis, EPR and NMR spectroscopies, and theoretical calculations. <a>The synthetic transformation described in this report results in the facile net reduction of CO₂at room temperature by lithium, sodium, and potassium metal without the need for additional metallic promoters, catalysts, or reagents – a process which does not occur in the absence of carbene.</a>

The 3-Dimensional g-Deformed Harmonic Oscillator and a Unified Description of Magic Numbers of Metal Clusters

Magic numbers predicted by a 3-dimensional (/-deformed harmonic oscillator with u9(3) D soq(3) symmetry are compared to experimental data for atomic clusters of alkali metals (Li, Na, K, Rb, Cs), noble metals (Cu, Ag, Au), divalent metals (Zn, Cd), and trivalent metals (Al, In), as well as to theoretical predictions of jellium models, Woods-Saxon and wine bottle potentials, and to the classification scheme using the 3n + / pseudo quantum number. In alkali metal clusters and noble metal clusters the 3-dimensional çr-deformed harmonic oscillator correctly predicts all experimentally observed magic numbers up to 1500 (which is the expected limit of validity for theories based on the filling of electronic shells), while in addition it gives satisfactory results for the magic numbers of clusters of divalent metals and trivalent metals, thus indicating that ug(3), which is a nonlinear extension of the u(3) symmetry of the spherical (3-dimensional isotropic) harmonic oscillator, is a good candidate for being the symmetry of systems of several metal clusters.

Surface Plasmon Assisted Two-Photon Ionization of Noble and Alkali Metal Clusters

In this communication we calculate the TPI cross-section for pump-probe scheme in Au, Ag and Na neutral clusters in high refractive index environment. The pump photon energy is chosen to be close to the surface plasmon (SP) energy of considered clusters. Since the interband transition energy in Ag and Na exceeds the SP resonance energy, the main contribution into the TPI in these clusters comes from the interband transitions. In Au clusters the interband transition threshold is very close to SP resonance, and the SP assisted TPI cross-section is attenuated. The calculations are performed by separating the coordinates of electrons corresponding to the collective oscillations and the individual motion that allows to take into account the resonance contribution of excited SP oscillations. It is shown that the ionization cross section increases by two orders of magnitude if the energy of the pump photon matches the surface plasmon energy in the Ag and Na cluster.