246 research outputs found
Sigma-Bond-to-Ligand Charge Transfer Transitions and Excited States of d6 Metal-Diimine Complexes.
Government Response to Political Activism: Conflict between the Public and the State, Genoa 2001
Protests represent an extremely delicate issue for governments and authorities in terms of security and democracy. Most recently in the last decade, demonstrations have acquired a global and international characterisation, rendering these trans-national phenomena. This research is a case study which aims to contribute to the political development of Italy by analysing the policies in relation to the management of protests by using theoretical frameworks drawn from fields of social and political sciences such as Public Policy and Peace and Conflict studies. The goal of this research is to analyse events in a broader picture, investigating democratic values and state response to social movements such as protests. In other words, it seeks to answer the following questions: How was the government response conceived and what impact did this have on state values of security, democracy and justice? Considering comparable cases, what was the impact in terms of policy and practice of these strategies? How can public policy theories of social construction help to explain the government response and thus contribute to prevention of such violence in future
Direct Observation of Quantum Coherence in Single-Molecule Magnets
Direct evidence of quantum coherence in a single-molecule magnet in frozen
solution is reported with coherence times as long as T2 = 630 ns. We can
strongly increase the coherence time by modifying the matrix in which the
single-molecule magnets are embedded. The electron spins are coupled to the
proton nuclear spins of both the molecule itself and interestingly, also to
those of the solvent. The clear observation of Rabi oscillations indicates that
we can manipulate the spin coherently, an essential prerequisite for performing
quantum computations.Comment: 5 Pages, 4 Figures, final version published in PR
Coupling molecular spin centers to microwave planar resonators: towards integration of molecular qubits in quantum circuits
We present spectroscopic measurements looking for the coherent coupling between molecular magnetic centers and microwave photons. The aim is to find the optimal conditions and the best molecular features to achieve the quantum strong coupling regime, for which coherent dynamics of hybrid photon-spin states take place. To this end, we used a high critical temperature YBCO superconducting planar resonator working at 7.7 GHz and at low temperatures to investigate three molecular mononuclear coordination compounds, namely (PPh4)2[Cu(mnt)2] (where mnt2- = maleonitriledithiolate), [ErPc2]-TBA+ (where pc2- is the phtalocyaninato and TBA+ is the tetra-n-butylammonium cation) and Dy(trensal) (where H3trensal = 2,2′,2′′-tris(salicylideneimino)triethylamine). Although the strong coupling regime was not achieved in these preliminary experiments, the results provided several hints on how to design molecular magnetic centers to be integrated into hybrid quantum circuits
An iridium(III/IV/V) redox series featuring a terminal imido complex with triplet ground state
Rotaxane Co-II Complexes as Field-Induced Single-Ion Magnets
Mechanically chelating ligands have untapped potential for the engineering of metal ion properties. Here we demonstrate this principle in the context of CoII-based single-ion magnets. Using multi-frequency EPR, susceptibility and magnetization measurements we found that these complexes show some of the highest zero field splittings reported for five-coordinate CoII complexes to date. The predictable coordination behaviour of the interlocked ligands allowed the magnetic properties of their CoII complexes to be evaluated computationally a priori and our combined experimental and theoretical approach enabled us to rationalize the observed trends. The predictable magnetic behaviour of the rotaxane CoII complexes demonstrates that interlocked ligands offer a new strategy to design metal complexes with interesting functionality
Spin dynamics in molecular ring nanomagnets: Significant effect of acoustic phonons and magnetic anisotropies
The nuclear spin-lattice relaxation rate 1/T_1_ is calculated for magnetic
ring clusters by fully diagonalizing their microscopic spin Hamiltonians.
Whether the nearest-neighbor exchange interaction J is ferromagnetic or
antiferromagnetic, 1/T_1_ versus temperature T in ring nanomagnets may be
peaked at around k_B_T=|J| provided the lifetime broadening of discrete energy
levels is in proportion to T^3^. Experimental findings for ferromagnetic and
antiferromagnetic Cu^II^ rings are reproduced with crucial contributions of
magnetic anisotropies as well as acoustic phonons.Comment: 5 pages with 5 figures embedded, to be published in J. Phys. Soc.
Jpn. 75, No. 10 (2006
Asymmetric Lineshape due to Inhomogeneous Broadening of the Crystal-Field Transitions in Mn12ac Single Crystals
The lineshape of crystal-field transitions in single crystals of Mn12ac
molecular magnets is determined by the magnetic history. The absorption lines
are symmetric and Gaussian for the non-magnetized state obtained by zero-field
cooling (zfc). In the magnetized state which is reached when the sample is
cooled in a magnetic field (fc), however, they are asymmetric even in the
absence of an external magnetic field. These observations are quantitatively
explained by inhomogeneous symmetrical (Gaussian) broadening of the
crystal-field transitions combined with a contribution of off-diagonal
components of the magnetic susceptibility to the effective magnetic
permeability.Comment: 4 pages, 3 figure
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