Vibrational

By the analytical results it has been possible to understand the different nature and composition of the materials employed in preparation of ancient cosmetic powders. Dark black powders were essentially composed of amorphous carbon probably due to the carbonisation of vegetal ...

... Spectroscopy, 6 (1993) 55-69 Elsevier Science Publishers BV, Amsterdam Investigation of melamine-formaldehyde cure by Fourier transform Raman spectroscopy ML Scheepers, JM Gelan, RA Carleer, PJ Adriaensens and DJ Vanderzande Limburg University, Department ...

... e librario, Laboratory of Chemistry, Via Milano 76, 00184 Roma, Italy; +39 0648291217, marina.bicchieri@beniculturali.it; michela.monti@beniculturali.it ... Manuscript 3 description of skins preparation for writing hasn t been found, an idea of the applied materials and methods can ...

Ni–Al hydrotalcite-like compounds with the general formula [Ni 1−x Al x (OH) 2 ](CO 3 ) x/2 mH 2 O, where 0.25≤x≤0.66, were synthesised using coprecipitation at a constant pH, and were treated hydrothermally. The structures of the oxidic forms obtained by calcination of the ...

Syngenite (K2Ca(SO4)2.H2O), formed during treatment of manure with sulphuric acid, was studied by infrared, near-infrared and Raman spectroscopy. Cs site symmetry was determined for the 2 sulphate groups in syngenite (P21/m), so all bands are both infrared and Raman active. The split ￮1 (2 Raman + 2 infrared bands) was observed at 981 and 1000 cm-1. The split ￮2 (4 Raman + 4 infrared bands) was observed in the Raman spectrum at 424, 441, 471 and 491 cm-1. In the infrared spectrum only 1 band was observed at 439 cm-1. From the split ￮3 (6 Raman + 6 infrared) bands 3 298 K Raman bands were observed at 1117, 1138 and 1166 cm-1. Cooling to 77 K resulted in 4 bands at 1119, 1136, 1144 and 1167 cm-1. In the infrared spectrum 5 bands were observed at 1110, 1125, 1136, 1148 and 1193 cm-1. From the split ￮4 (6 infrared + 6 Raman bands) 4 bands were observed in the infrared spectrum at 604, 617, 644 and 657 cm-1. The 298 K Raman spectrum showed 1 band at 641 cm-1, while at 77 K 4 bands were observed at 607, 621, 634 and 643 cm-1. Crystal water is observed in the infrared spectrum by the OH-libration mode at 754 cm-1, OH-bending mode at 1631 cm-1, OH-stretching modes at 3248 (symmetric) and 3377 cm-1 (antisymmetric) plus a combination band at 3510 cm-1 of the H-bonded OH-mode plus the OH-stretching mode. The near-infrared spectrum gave information about the crystal water resulting in overtone and combination bands of OH-libration, OH-bending and OH–stretching modes

The application of infrared spectroscopic imaging to non-destructive examination of works of art is described. Its advantages over infrared photography and reflectography are discussed, in particular its ability to provide spectroscopic information, which potentially allows identification of pigments, binders, and other materials. Near-infrared spectra of a selection of brown and black pigments are presented. Results are given of the application of infrared spectroscopic imaging to two works of art in different media: an ink drawing and an oil painting.

Near-IR spectroscopic imaging was used to analyze the remnants of a work of art, a 16th century drawing, attributed to the School of Pieter Bruegel the Elder, which had been significantly altered during a cleaning attempt. Using a combination of a CCD camera and a liquid crystal tunable filter (LCTF), near-IR spectroscopic images (650–1050 nm) were collected from the drawing and from a test sample composed of four substances with differing near-IR spectra deposited on a whiteboard surface. Both supervised and unsupervised classification methodologies (linear discriminant analysis (LDA) and fuzzy C-means (FCM) clustering, respectively) were used to analyze the data. FCM clustering, in combination with several spectral normalization routines, proved an excellent data exploration method for the test sample. LDA gave consistently clearer results than the FCM methods, but required a priori knowledge of the spectral properties of the sample, provided, in this case, by the FCM analysis. LDA of the spectroscopic image of the work of art revealed clearly and for the first time the location of regions of the drawing where faint traces of ink residue remained.

Electronic and vibrational spectra of two different tourmalines: green and pink coloured minerals from Minas Gerais, Brazil, have been investigated by UV–vis, NIR, IR and Raman spectroscopies. The behaviour of transition metal ions in their electronic spectra is presented. Both minerals show a strong broad band at 300 nm (33,300 cm-1) due to Mn(II) ion. In pink tourmaline three sharp bands at 365, 345, and 295 nm
(27,400, 28,990 and 33,900 cm-1) are assigned to 6A1g (S)1 4T2g (D), 6A1g (S) 4Eg (D) and 6A1g (S) 4T1g (F) transitions of Mn(II) ion. The pink colour arises from the Mn(II) ion while the band at 520 nm comes from Mn(III) ion which acts as an aid to the transmission window from 700 to 900 nm in pink tourmaline. NIR spectroscopy provides evidence for Fe(II) through the observation of two bands at 10,240 and 8000 cm-1. The observation of four OH stretching bands in the hydroxyl stretching region 3800–3200 cm-1 near 3650, 3600 and 3555 and 3460 cm-1 shows mixed occupancy of octahedral sites in the minerals studied. The band positions in the spectra of green and pink tourmalines differ slightly due to compositional variations. Experimentally, a number of cation–oxygen vibrational modes in the Raman spectra could be observed in the low wavenumber region 1200–200 cm-1.