Ricerc@Sapienza

Mineral evolution is concerned with the timing of mineral occurrences, such as the earliest reported occurrences in the geologic record. Minerals containing essential Li have not been reported from rocks older than ca. 3000 Ma, thus the lithian tourmaline (fluor-elbaite) and mica (lepidolite) assemblage from a pegmatite near Zishineni associated with the ca. 3000 Ma Sinceni Pluton presents unusual interest. Fluor-elbaite (0.75-0.98 F per formula unit) forms green crystals up to 50 trim long. Spindle stage measurements give omega = 1.652(1), epsilon = 1.627(1) (589.3 nm).

Natural Mg-rich lucchesiite was thermally treated in air and hydrogen atmosphere up to 800 °C to study potential changes in Fe-, Mg- and Al ordering over the octahedrally coordinated Y- and Z-sites, and to explore possible applications to intracrystalline geothermometry based on tourmaline. Overall, the experimental data (structural refinement, Mössbauer, infrared and optical absorption spectroscopy) show that thermal treatment of lucchesiite results in an increase of Fetotcontents at Z balanced by an increase of Mg and Al at Y.

An Fe-rich fluor-elbaite was thermally treated in air and hydrogen atmosphere up to 800 °C to study potential changes in Fe- and Al-ordering over the octahedrally coordinated Y and Z sites. Overall, the experimental data (structural refinement, electron and ion microprobe, Mössbauer, infrared and optical absorption spectroscopy) show that thermal treatment of fluor-elbaite results in an increase of Fe contents at the Z site balanced by an increase of Al at the Y site.

Ettringite, reported with ideal formula Ca6Al2(SO4)3(OH)12·26H2O, is recognized as a secondary-alteration mineral and as an important crystalline constituent of Portland cements, playing different roles at different time scales. It contains more than 40 wt% of H2O. The crystal structure and crystal chemistry of ettringite were investigated by electron microprobe analysis in wavelength-dispersive mode, infrared spectroscopy, and single-crystal neutron diffraction at 20 K.

Diamonds and their inclusions are unique fragments of deep Earth, which provide rare samples from inaccessible portions of our planet. Inclusion-free diamonds cannot provide information on depth of formation, which could be crucial to understand how the carbon cycle operated in the past. Inclusions in diamonds, which remain uncorrupted over geological times, may instead provide direct records of deep Earth’s evolution.

Germanium-on-silicon waveguides were modeled, fabricated and characterized at wavelengths ranging from 7.5 to 11 µm. Measured waveguide losses are below 5 dB/cm for both TE and TM polarization and reach values of ∼ 1 dB/cm for ≥ 10 µm wavelengths for the TE polarization. This work demonstrates experimentally for the first time that Ge-on-Si is a viable waveguide platform for sensing in the molecular fingerprint spectral region.

We report on an orbital and temperature dependent study of the onset of coherent quasiparticles in V2O3 single crystal. By using polarized infrared spectroscopy we demonstrate that the electronic coherence temperature is strongly orbital dependent, being about 400 K for e?g orbitals and 500 K for the a1g. This suggests that V2O3 low energy electrodynamics can be described in terms of two electron liquids differently renormalized by electronic correlations.

La cristallizzazione da fuso del polipropilene isotattico è stata studiata in condizioni dinamiche mediante un’implementazione dell’FTIR a temperatura variabile. Per questo scopo, gli spettri sono acquisiti sequenzialmente durante un programma di temperatura che prevede una rampa di raffreddamento lineare con sovrimposta una funzione periodica (Temperature Modulated FTIR, TMFTIR).