Search results for "RAMAN"
showing 10 items of 1328 documents
INDAGINI DIAGNOSTICHE PROPEDEUTICHE AL RESTAURO DELLA SALA DEI VENTI DI PALAZZO DEI NORMANNI A PALERMO
2019
La Sala dei Venti è uno dei più suggestivi luoghi del Palazzo dei Normanni a Palermo, si tratta di una struttura sita all’interno della Gioaria, una torre medievale dell’originale nucleo arabo-normanno, antistante la Sala di Ruggero, coperta da un soffitto ligneo dipinto, risalente al XVIII secolo, al centro del quale campeggia una rosa dei Venti che dà il nome all’ambiente. Le porzioni superiori delle pareti e la copertura, soggette nel tempo a numerosi restauri e rifacimenti, presentano una ricca decorazione dipinta suddivisa in tre livelli: quello superiore costituito dal soffitto dipinto (parzialmente incamottato); quello intermedio costituito dai dipinti murali con decorazioni a finto …
Raman spectroscopy of the high- and low-spin states of the spin crossover complex Fe(phen)2(NCS)2: an initial approach to estimation of vibrational c…
2000
Abstract Raman spectra of the spin-crossover complex Fe(phen)2(NCS)2 in the solid state have been recorded at 785 nm as a function of temperature to investigate the contribution of intramolecular vibrations to the entropy change, ΔS, associated with spin crossover. The modes of major interest for estimating the contribution lie in the range 100–500 cm−1, where the largest qualitative changes with temperature in the Raman spectra were observed. Analysis of these data, with the working assumption of an average frequency in this range as representative of the 15 distortion modes of an idealised FeN6 octahedron, leads to the conclusion that the intramolecular vibrations represent a primary cont…
Light induced excited spin state trapping in the binuclear spin crossover compound [Fe(bpym)(NCS)2]2(bpym) exhibiting a high-spin ground state
2008
Abstract A photo-magnetic effect is evidenced using near-infrared light in the binuclear complex [Fe(bpym)(NCS) 2 ] 2 (bpym). This compound has a 5 T 2g – 5 T 2g ground state and exhibits no thermal spin crossover – in contrast to the analogous [Fe(bpym)(NCSe) 2 ] 2 (bpym). The estimated photo-conversion ratio is ca. 30%. By means of magnetic susceptibility measurements as well as Raman and infrared absorption spectroscopies, the nature of the photo-induced phase was established as the 5 T 2g – 1 A 1g state, which means that only one iron center is converted to low-spin. The photo-induced state was completely converted back to the ground state either by visible light excitation or by heatin…
Thermal and pressure-induced spin crossover in a novel three-dimensional Hoffman-like clathrate complex
2011
The synthesis and crystal structure of the interpenetrated metal–organic framework material Fe(bpac)2[Ag(CN)2]2 (bpac = 4,4′-bis(pyridyl)acetylene) are reported along with the characterization of its spin crossover properties by variable temperature magnetometry and Mossbauer spectroscopy. The complex presents an incomplete stepped spin transition as a function of temperature that is modified upon successive thermal cycling. The pressure-induced transition has also been investigated by means of high pressure Raman spectroscopy using a diamond anvil cell. The results show that it is possible to reach the thermally-inaccessible fully low spin state at room temperature by applying hydrostatic …
Defects induced by He+ irradiation in γ-Si3N4
2021
International audience; Formation and evolution of defect levels in the electronic structure of silicon nitride with cubic spinel structure, -Si 3 N 4 , after the irradiation with He + ions was investigated using spectroscopic techniques. Strong changes of cathodoluminescence (CL), photoluminescence (PL), photoluminescence excitation (PLE) and Raman spectra were detected. In particular, excitonic PL was significantly inhibited and a new near-IR band appeared with the band gap excitation h≥E g =5.05 eV. This was explained by an effective trapping of photoinduced electrons and holes by charged defects. The spectral shift of PL with the excitation photon energy indicated heterogeneous nature…
Time-dependent perturbation treatment of independent Raman schemes
2007
The problem of a trapped ion subjected to the action of two or more independent Raman schemes is analysed through a suitable time-dependent perturbative approach based on the factorization of the evolution operator in terms of other unitary operators. We show that the dynamics of the system may be traced back to an effective Hamiltonian up to a suitable dressing. Moreover, we give the method to write the master equation corresponding to the case wherein spontaneous decays occur.
On heterocyclic systems containing bismuth(III) 2. Eight-membered heterocycles Cl/Br/I-M(CH2CH2CH2)2X with lewis acidic group 15 atoms M As, Sb, Bi…
1994
Abstract Paths to the ligands (Cl/Br-CH2CH2CH2)2NR/O/S/Se, R Me, Bz, iPr, iBu, to the diGrignard reagents (Cl/BrMg-CH2CH2CH2)2NR/O/S, R Me, Bz, iPr, iBu and to the eight-membered group 15 heterocycles (Cl/Br/I-As/Sb/Bi(CH2CH2CH2)2NR/S, R Me, Bz, iBu are given. 13C-NMR, IR and Raman spectra are discussed; for the compound ClSb(CH2CH2CH2)2NMe the crystal structure analysis is given : the antimony atom is clearly Lewis acidic with ψ-trigonal-bipyramidal coordination and a transannular Sb⋯N interaction of 2.385(2) A. For such a configuration the values of the 13C-NMR chemical shifts of the α-CH2-groups (e.g. Cl-As/Sb/Bi(αCH2CH2CH2)2NMe 34.6, 25.9, 46.6 ppm) display clearly a sequence N > …
Molecular materials with conducting and magnetic properties based on ET and [ M(tdas)2]x-dithiolenes
2004
Two hybrid molecular materials showing a combination of magnetic and conducting properties, the charge-transfer (ET) 2 [Fe(tdas) 2 ] (1) and (ET)Ni(tdas) 2 (2), (ET=bis(ethylenedithio) tetrathiafulvalene; M=Fe, Ni; tdas=l,2,5-thiadiazole-3,4-dithiolate) salts, are characterized by vibrational (IR and Raman) and UV-VIS-NIR spectroscopies. These studies have proved to be effective and diagnostic tools in identifying the oxidation state (partial or integer) and the packing pattern (dimers or segregated stacks) of the ET donor only, since no v(C=C) group vibration sensitive to the charge of M(tdas) 2 complexes has been observed. This is ascribed to the extensive electron-delocalization inside t…
Über polyplumbane
1985
Abstract Diplumbanes Pb 2 R 3 R′ 3 (R,R′ = Ph, o -Tol, p -Tol) have been synthesized from R 3 PbLi and R′ 3 PbCl at −60°C in THF. Mass, 13 C and 207 Pb NMR spectra of the products exhibit migrations of R, R′ in the transition state (R 3 PbLi + ClPbR′ 3 ) leading to a complex distribution of the substituents (δ( 207 Pb) with respect to PbMe 4 −70 to −95 ppm). The PbPb stretching vibration (100 to 115 cm −1 ) couples with a lattice vibration giving rise to a single intensive Raman line. The crystal structure of Pb 2 Ph 3 ( p -Tol) 3 has been determined and refined to R = 0.155. Two independent molecules are disordered and have identical distribution of the substituents Ph( p -Tol) 2 PbPbPh …
A new tetranuclear copper(I) complex based on allyl(5-phenyl-1,3,4-thiadiazol-2-yl)azanide ligand: Synthesis and structural characterization
2015
Abstract By means of alternating current electrochemical technique a new tetranuclear crystalline copper(I) complex [Cu I 4 ( L − ) 4 ] ( L − – allyl(5-phenyl-1,3,4-thiadiazol-2-yl)azanide ion) has been obtained and characterized by X-ray single crystal diffraction ( Sp. gr. I 4 1 / a ) and Raman spectroscopy. The metal center adopts linear arrangement, composed of one thiadiazole N atom from the one L − anion and one azanide N atom of the other L − ligand. A bridged Cu atoms stitch four L − ligands into the firstly observed tetranuclear copper(I) azanide complex with intramolecular Cu(I)⋯Cu(I) interactions at the distance of 2.7451(6) A. Molecular structure and Raman spectrum of the compo…