Persona: Gavira Vallejo, José María
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Gavira Vallejo
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José María
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Publicación Rock Art(The Royal Society of Chemistry, 2021-06-04) Hernanz, Antonio; Gavira Vallejo, José MaríaAn overview of representative studies on rock art paintings applying physicochemical techniques to investigate their composition is presented. Advantages and limitations of the different techniques, protocols and recommendations for sampling and proposals to deal with difficulties are discussed. Portable instrumentation and non-destructive multi-technique methodology are highly advisable. Contamination and the presence of non-pictorial materials must always be taken into account because rock art is an open-air scenario. Accretions, alterations, deterioration and possible remedies are considered. The results obtained are very useful for archaeologists and conservators. The use of new techniques and instrumentation augurs a promising future in this field.Publicación Micro-Raman spectroscopy of rock paintings from the Galb Budarga and Tuama Budarga rock shelters, Western Sahara(Elsevier, 2018-03) Iriarte, Mercedes; Hernanz, Antonio; Sáenz de Buruaga, Andoni; Gavira Vallejo, José María; Martín Fernández, SantiagoRock paintings of two recent discovered rock shelters, Galb Budarga and Tuama Budarga, from the southeastern area of the Western Sahara, Sahrawi Arab Democratic Republic, have been studied by micro-Raman spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray spectrometry in order to characterize the composition of the materials present in the painting panels. An unusual white pigment has been used in the zoomorphic pictographs of the Galb Budarga shelter which main components are the anhydrite (CaSO4) polymorphs I and II. Red and orange zoomorphic figures and ancient Berber scripts have been painted in the Tuama Budarga rock shelter. Haematite (α-Fe2O3) is the main component of the paints used; amorphous carbon and different manganese oxides have also been detected. Accretions of gypsum (CaSO4·2H2O) and anhydrite have been observed on the shelter wall used to paint. α-Quartz (α-SiO2), albite (NaAlSi3O8), dolomite, CaMg(CO3)2, calcite (CaCO3) and traces of hydroxylapatite (Ca10(PO4)6(OH)2) have been identified in the rocks supporting the paintings of both sites. Layers of calcium oxalates, whewellite (CaC2O4·H2O) and weddellite (CaC2O4·(2 + x)H2O, x ≤ 0.5) cover the pictorial panels of these rock shelters. A microestratrigraphic study of the paint used in the Tuama Budarga shelter revealed that the pigment layer is bracketed between oxalate layers.Publicación Micro Raman Spectroscopy of Epipalaeolithic Decorated Pebbles from Arroyo Moreras 2 (Parque Darwin, Madrid)(The Royal Society of Chemistry, 2019-11) Hernanz, Antonio; Bueno Ramírez, Primitiva; Balbín Behrmann, Rodrigo de; Morín de Pablos, Jorge; Juana Ortín, Cristina de; Gavira Vallejo, José MaríaPigment vestiges on the three decorated pebbles from the excavation of Parque Darwin (Madrid), level 8470 ± 70 BP have been identified by Micro Raman Spectroscopy. Haematite and amorphous carbon were used as pigments. Microscopic contamination spots with ε-copper-phthalocyanine blue, have been detected. The analysis of the pigments used, together with their previously unknown chronology and open-air location, constitute a new point of reference for the technical and cultural uses of symbology among hunter-gatherers in southern Europe.Publicación A comprehensive study of the molecular vibrations in solid-state benzylic amide [2]catenane(Royal Society of Chemistry, 2019) Romero Muñiz, Carlos; Paredes Roibás, Denís; Hernanz, Antonio; Gavira Vallejo, José MaríaThe interpretation of vibrational spectra is often complex but a detailed knowledge of the normal modes responsible for the experimental bands provides valuable information about the molecular structure of the sample. In this work we record and assign in detail the infrared (IR) spectrum of the benzylic amide [2]catenane, a complex molecular solid displaying crimped mechanical bonds like the links of a chain. In spite of the large size of the unit cell, we calculate all the vibrational modes of the catenane crystal using quantum first-principles calculations. The activity of each mode is also evaluated using the Born effective charges approach and a theoretical spectrum is constructed for comparison purposes. We find a remarkable agreement between the calculations and the experimental results without the need to apply any further empirical correction or fitting to the eigenfrequencies. A detailed description in terms of the usual internal coordinates is provided for over 1000 normal modes. This thorough analysis allows us to perform the complete assignment of the spectrum, revealing the nature of the most active modes responsible for the IR features. Finally, we compare the obtained results with those of Raman spectroscopy, studying the effects of the rule of mutual exclusion in vibrational spectroscopy according to the different levels of molecular symmetry embedded in this mechanically interlocked molecular compound.Publicación Assignment of the Raman Spectrum of Benzylic Amide [2]Catenane: Raman Microscopy Experiments and First-Principles Calculations(American Chemical Society, 2018) Romero Muñiz, Carlos; Paredes Roibás, Denís; Hernanz, Antonio; López García, Concepción; Gavira Vallejo, José MaríaIn this work, we use Raman spectroscopy and quantum first-principles calculations to unveil the experimental spectrum of a complex molecular solid-like benzylic amide [2]catenane, a representative example of a mechanically interlocked molecular architecture. We use large-scale density functional theory calculations to obtain the complete set of vibrational normal modes of the catenane crystal, whose unit cell contains 544 atoms. Subsequently, we demonstrate that these calculations are able to accurately reproduce the experimental Raman spectrum of this molecular compound, without introducing any empirical corrections or fittings in the calculated eigenfrequencies. Thanks to the good agreement between the experimental and theoretical spectra, it is possible to carry out the complete assignment of the main vibrational modes responsible for the whole spectrum. A detailed description in terms of the usual internal coordinates is given for all of these representative modes. This description, rather difficult from the experimental point of view, provides valuable information about the molecular structure of this compound, compatible with experimental evidences reported in the literature.