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We report resonance Raman scattering (RRS) spectra and Raman excitation profiles (REP) of a system containing π dimers of identical molecular radical ions measured with laser excitation in resonance with the charge transfer (CT) transition. A Peierls–Hubbard (PH) Hamiltonian has been used to model the investigated system and to calculate its optical and RRS properties. Results are reported for two polyoxometallate salts of tetrathiafulvalene (TTF), namely (TTF)2(W6O19) and (TTF)2(Mo6O19) whose structures contain almost isolated (TTF+)2 dimers. The RRS spectra of (TTF)2(W6O19), measured in resonance with the CT absorption band centered at 832 nm, show three phonon modes located at 55, 90, and 116 cm-1 which are strongly resonance enhanced. These modes have been associated to the out-of-phase combinations of the translational motions of the two molecules composing the dimer. Such modes are effective in modulating the intradimer transfer integral, thus providing an efficient mechanism for coupling with the electronic system and for enhancement of the scattering intensity at resonance with the CT transition. The REP for the three strongly coupled modes of (TTF)2(W6O19) have been measured with laser excitation wavelengths ranging from 740 to 930 nm. Quantitative analysis of the REP data has been performed based on a perturbative solution of the PH model to second order in the electron-molecular-vibration (EMV) and electron-intermolecular-phonon (EIP) interactions. The CT absorption profile and the REP’s have been calculated using a time correlator technique and the model parameters have been optimized in order to fit the experimental REP data. Infrared vibronic absorptions of (TTF)2(W6O19), originated by the EMV coupling, have been measured and independent information on the electronic parameters of the PH model have been derived. This has made the choice of the fitting parameters used for the REP calculations rather unambiguous and has allowed us... [ABSTRACT FROM AUTHOR]

The aim of this archaeometric study is to recover information regarding technological processes and raw materials used for the production of ceramic sherds coming from five central and Eastern German sites, between Lower Saxony and Saxony states. The ceramic fragments have been investigated by a multi-spectroscopic approach: Fourier transform infrared spectroscopy (FT-IR), micro-Raman spectroscopy and X-ray Fluorescence (XRF) were employed to characterize both ceramic bodies and glazes. Moreover the innovative application of Laser Induced Fluorescence (LIF) on ceramic findings has been proposed and evaluated. Chemical and mineralogical composition, as well as microstructure, of ceramic mixture and glaze are correlated to native material composition and firing temperature, which have become a fundamental features in archaeometric research and play a key role in understanding the provenance of the pottery and its production techniques. The multi-spectroscopic approach applied in this work has enabled the ability to characterize the ceramic sherds and to investigate through non-destructive techniques both ceramic glaze and matrix giving information regarding the raw materials and pigments/colourants used, and regarding firing temperature and technology. The present study carried on using complementary methods suggests different raw material sources and temperature kilns. These data are in agreement with the location of ceramic sites and with data in literature. Furthermore, the interesting results suggest that non-destructive techniques, such as LIF and Raman spectroscopy, are promising methods for ceramic and glaze characterization. [ABSTRACT FROM AUTHOR]

Two new minerals - manganoblödite (IMA2012-029), ideally Na2Mn(SO4)2·4H2O, and cobaltoblödite (IMA2012-059), ideally Na2Co(SO4)2·4H2O, the Mn-dominant and Co-dominant analogues of blödite, respectively, were found at the Blue Lizard mine, San Juan County, Utah, USA. They are closely associated with blödite (Mn-Co-Ni-bearing), chalcanthite, gypsum, sideronatrite, johannite, quartz and feldspar. Both new minerals occur as aggregates of anhedral grains up to 60 μm (manganoblödite) and 200 μm (cobaltoblödite) forming thin crusts covering areas up to 2 × 2 cm on the surface of other sulfates. Both new species often occur as intimate intergrowths with each other and also with Mn-Co-Ni-bearing blödite. Manganoblödite and cobaltoblödite are transparent, colourless in single grains and reddish-pink in aggregates and crusts, with a white streak and vitreous lustre. Their Mohs' hardness is ~2½. They are brittle, have uneven fracture and no obvious parting or cleavage. The measured and calculated densities are Dmeas = 2.25(2) g cm−3 and Dcalc = 2.338 g cm−3 for manganoblödite and Dmeas = 2.29(2) g cm−3 and Dcalc = 2.347 g cm−3 for cobaltoblödite. Optically both species are biaxial negative. The mean refractive indices are α = 1.493(2), β = 1.498(2) and γ = 1.501(2) for manganoblödite and α = 1.498(2), β = 1.503(2) and γ = 1.505(2) for cobaltoblödite. The chemical composition of manganoblödite (wt.%, electron-microprobe data) is: Na2O 16.94, MgO 3.29, MnO 8.80, CoO 2.96, NiO 1.34, SO3 45.39, H2O (calc.) 20.14, total 98.86. The empirical formula, calculated on the basis of 12 O a.p.f.u., is: Na1.96(Mn0.44Mg0.29Co0.14Ni0.06)Σ0.93S2.03O8·4H2O. The chemical composition of cobaltoblödite (wt.%, electron-microprobe data) is: Na2O 17.00, MgO 3.42, MnO 3.38, CoO 7.52, NiO 2.53, SO3 45.41, H2O (calc.) 20.20, total 99.46. The empirical formula, calculated on the basis of 12 O a.p.f.u., is: Na1.96(Co0.36Mg0.30Mn0.17Ni0.12)Σ 0.95S2.02O8·4H2O. Both minerals are monoclinic, space group P21/a, with a = 11.137(2), b = 8.279(1), c = 5.5381(9) Å, β = 100.42(1)°, V = 502.20(14) Å3 and Z = 2 (manganoblödite); and a = 11.147(1), b = 8.268(1), C = 5.5396(7) Å, β = 100.517(11)°, V = 501.97(10) Å3 and Z = 2 (cobaltoblödite). The strongest diffractions from X-ray powder pattern [listed as (d,Å(I)(hkl)] are for manganoblödite: 4.556(70)(210, 011); 4.266(45)(2̅01); 3.791(26)(2̅11); 3.338(21)(310); 3.291(100)(220, 021), 3.256(67)(211,1̅21), 2.968(22)(2̅21), 2.647(24)(4̅01); for cobaltoblödite: 4.551(80)(210, 011); 4.269(50)(2̅01); 3.795(18)(2̅11); 3.339(43)(310); 3.29(100)(220, 021), 3.258(58)(211, 1̅21), 2.644(21)( 4̅01), 2.296(22)( 1̅22). The crystal structures of both minerals were refined by single-crystal X-ray diffraction to R1 = 0.0459 (manganoblödite) and R1 = 0.0339 (cobaltoblödite). [ABSTRACT FROM AUTHOR]

Tazzoliite, ideally Ba2CaSr0.5Na0.5Ti2Nb3SiO17[PO2(OH)2]0.5, is a new mineral (IMA 2011-018) from Monte delle Basse, Euganei Hills, Galzignano Terme, Padova, Italy. It occurs as lamellar pale orange crystals, which are typically a few m m thick and up to 0.4 mm long, closely associated with a diopsidic pyroxene and titanite. Tazzoliite is transparent. It has a white streak, a pearly lustre, is not fluorescent and has a hardness of 6 (Mohs'' scale). The tenacity is brittle and the crystals have a perfect cleavage along {010}. The calculated density is 4.517 g cm–3. Tazzoliite is biaxial (–) with 2Vmeasof ~50º, it is not pleochroic and the average refractive index is 2.04. No twinning was observed. Electronmicroprobe analyses gave the following chemical formula: (Ba1.93Ca1.20Sr0.52Na0.25Fe2+0.10)Σ4 (Nb2.88Ti2.05Ta0.07Zr0.01V5+0.01)Σ5.02SiO17[(P0.13Si0.12S0.07)Σ0.32O0.66(OH)0.66][F0.09(OH)0.23]Σ0.32.Tazzoliite is orthorhombic, space group Fmmm, with unit-cell parameters a= 7.4116(3), b= 20.0632(8), c= 21.4402(8) Å, V= 3188.2(2) Å3and Z= 8. The crystal structure, obtained from single-crystal X-ray diffraction data, was refined to R1(F2) = 0.063. It consists of a framework of Nb(Ti) octahedra and BaO7polyhedra sharing apexes or edges, and Si tetrahedra sharing apexes with Nb(Ti) octahedra and BaO7polyhedra. The structure, which is related to the pyrochlore structure, contains three Nb(Ti) octahedra: two are Nb dominant and one is Ti dominant. Chains of A2O8polyhedra [A2 being occupied by Sr(Ca, Fe)] extend along [100] and are surrounded by Nb octahedra. Channels formed by six Nb(Ti) octahedra and two tetrahedra, or four A1O8(OH) polyhedra (A1 being occupied by Ba), alternate along [100]. The channels are partially occupied by [PO2(OH)2] in two possible mutually exclusive positions, alternating with fully occupied A3O7polyhedral pairs [A3 being occupied by Ca(Na)]. The seven strongest X-ray powder diffraction lines [din Å (I/I0) (hkl)] are: 3.66 (60) (044), 3.16 (30) (153), 3.05 (100) (204), 2.98 (25) (240), 2.84 (50) (064), 1.85 (25) (400) and 1.82 (25) (268). Raman spectra of tazzoliite were collected in the range 150–3700 cm–1and confirm the presence of OH groups. Tazzoliite is named in honour of Vittorio Tazzoli in recognition of his contributions to the fields of mineralogy and crystallography. [ABSTRACT FROM AUTHOR]

Abstract: In the restitic crustal enclaves in the Neogene volcanics of El Hoyazo and Mazarrón (SE Spain), associations of fluid and silicate melt inclusions indicative of immiscibility are frequently observed in the Bt-poor, Crd-rich graphitic metapelites. These occurrences, extremely rare for anatectic crustal rocks, have been studied by microthermometry, micro-Raman spectroscopy and EMP analysis. Both at El Hoyazo and Mazarrón the immiscible FI and MI are hosted in plagioclase and cordierite, with microstructures that suggest primary trapping. The FI hosted in cordierite are monophase, whereas they may contain crystals of calcite when hosted in plagioclase, indicating fluid–host reaction during cooling. Decrepitation microstructures have not been observed. The MI contain fresh glass of peraluminous, felsic rhyolitic composition, typical of anatectic S-type melts. In all samples the fluids are CO2-dominated (>85 mol%), with minor amounts of N2 and CH4, and traces of CO and H2. The nucleation of graphite, induced by the laser beam in some inclusions, demonstrates that the fluids are graphite-saturated. Large scatter in microthermometric behaviour of FI indicates significant density variations. Only in one sample from El Hoyazo are fluid densities compatible with the estimated P–T conditions of trapping (5–7 kbar, 850±50 °C), whereas in the remaining samples the extremely low densities, suggesting trapping pressures <1 kbar, are in contrast with the microstructural indications of primary entrapment and little evidence of decrepitation. In addition, although some measured compositions are compatible with C–O–H–N fluid speciation at the estimated P–T conditions of anatexis, the lack of H2O in all FI is inconsistent with the slightly hydrated character of coexisting glasses. The possible mechanisms accounting for departure of densities and compositions of FI from expected values are discussed, and leakage of H2O suggested as the most plausible. [Copyright &y& Elsevier]

The photoinduced chiroptical properties of an optically active methacrylic polymer bearing in the side-chain a conjugated trans-azoaromatic chromophore linked to the main chain through a chiral cyclic pyrrolidine moiety of one prevailing absolute configuration have been investigated. The polymeric film is characterized by a strong optical activity that can be amplified and reversibly modulated by irradiation with circularly polarized (CP) light at 488 nm. A remarkable modification of the shape of the circular dichroism (CD) spectrum after the initial irradiation steps is observed, with an amplification of the CD signal upon increasing the total irradiation fluence. The most important results are connected with the handedness of the CP radiation: left circularly polarized (CP-L) light is able to reverse the relative sign of the CD spectra, whereas by pumping with right circularly polarized (CP-R) radiation, it is possible to recover the original shape of the signal. This well reproducible and reversible effect suggests the possibility to use the investigated material for chiroptical switching. [Copyright &y& Elsevier]

Methacrylic polymers bearing in the side-chain the electron donor–acceptor conjugated trans-azoaromatic chromophore linked to the main chain through a chiral moiety of one prevailing absolute configuration, have been prepared and investigated as materials suitable to reversible optical storage. In addition to the induction of a significant birefringence, upon irradiation of the polymeric film with linearly polarized (LP) light, combined with a relevant stability and reproducibility after repeated writing–erasing cycles with linearly and circularly polarized (CP) light, respectively, the material exhibits inversion of chirality when the erasing step is performed with one-handed CP light of the opposite sense with respect to the original chirality handedness assumed by the material as a consequence of its intrinsically chiral structure. The process appears to be reversible, and the material may re-assume the original screw sense by irradiating with circularly polarized light of the appropriate sense, regardless previous ordering by irradiation with LP light has been performed. The sense of chirality assumed by the material upon irradiation with one-handed CP light is unaffected by heating; and annealing of the film at higher temperature, above the glass transition, produces an enhancement of the dichroic bands related to the electronic transitions of the azoaromatic chromophore. [Copyright &y& Elsevier]

We report the first example of a heterocycle-based multi-branched two-photon absorption (TPA) dye. We show that the new chromophore presents a very large TPA cross-section in the femtoseconds (fs) regime. Comparison of the TPA cross-sections between the branched system and the corresponding “monomeric unit” shows a strong cooperative enhancement. A value of 22.6:1, corresponding to a 750% enhancement, was observed. [Copyright &y& Elsevier]