Chemical Bonding of Transition-metal Co13_{13} Clusters with Graphene

We carried out density functional calculation to study Co$_{13}$ clusters on graphene. We deposit several free isomers in different disposition respect to hexagonal lattice nodes, studying even the $hcp$ $2d$ isomer recently obtained as the most stable one. Surprisingly, Co$_{13}$ clusters bonded to graphene prefer $icosahedron-like$ structures where the low lying isomer is much distorted, because it is linked with more bonds than in previous works. For any isomer the most stable position binds to graphene by the Co atoms that can lose electrons. We find that the charge transfers between graphene and clusters are small enough to conclude that the Co-graphene binding is not ionic-like but chemical. Besides, the same order of stability among the different isomers on doped graphene is well kept. These findings could also be of interest for magnetic clusters on graphenic nanostructures such as ribbons and nanotubes.Comment: 12 pages, 6 figure

ZEEMAN QUANTUM BEATS IN NO2NO_{2}: A STUDY OF EXCITED STATE ALIGNMENT AND RELAXATION

Author Institution:A single mode dye laser is used to selectively excite individual rotational levels in the $NO_{2}\ ^{2}B_{2+} ^{2}A_{1}$ visible transition. Subsequent time resolved fluorescence polarisation measurements in the presence of fixed magnetic field demonstrate quantum beats between Zeeman sublevels of each excited hyperfine component. A single measurement yields the radiative relaxation rate, the alignment relaxation rate, and the Lande g factor for each hyperfine component. These properties are in accord with simple theory. This experiment bears on discrepancies in previous measurements of these quantities by zero field level crossing (Hanle Effect), optical radio frequency double resonance, and pulsed laser induced fluorescence