Ricardo Torres

LIBS spectra of polychromes with a low cost CCD camera based detector

Abstract Two real samples of polychromes, from the Spanish Baroque period and from the XV century, were analysed by time-integrated laser-induced breakdown spectroscopy (LIBS). The time-integrated spectra showed negligible contribution of continuum background emission. The spectra of the Baroque sample indicated the presence of vermilion; this was confirmed by near-infrared Fourier transform spectroscopy. LIBS spectra of the XV century sample showed Ca, Al, Mg, Na and Pb lines and the molecular emissions CN(B-X) and C 2 (d-a). Relative spectral intensities were measured as a function of the number of laser pulses delivered at the same position of the sample.

ANALYTICAL STUDIES OF POLYCHROMES BY TIME-INTEGRATED LASER-INDUCED BREAKDOWN SPECTROSCOPY

Time integrated Laser Induced Breakdown Spectroscopy was applied to the study of real samples of polychromes. Two samples respectively from the Spanish Baroque and from the XV century were analysed. The time integrated spectra showed negligible contribution of continuum background emission. The spectra of the Baroque sample indicated the presence of vermilion; this was confirmed by Near Infrared Fourier Transform Spectroscopy. LIBS spectra of the XV century sample showed Ca, Al, Mg, Na and Pb lines and the molecular emissions CN(B-X) and C2(d-a). Relative spectral intensities were measured as a function of the number of laser pulses delivered on the same position of the sample. The LIBS analysis was compared to an exhaustive analytical study.

Coordination chemistry of titanium and zinc in Ti(1−x)Zn2xO2 (0 ≤ x ≤ 1) ultrathin films grown by DC reactive magnetron sputtering

XANES and RBS were used to explore the structural phase and composition transitions of ultrathin films with Ti(1−x)Zn2xO2 stoichiometries, from very low (∼0.5 at.%) to high (∼25 at.%) titanium content. In this way, the coordination chemistry of Ti4+ and Zn2+ cations was examined for a wide range of oxide compositions.

Rotational energy transfer in CD(A, v=0) in collisions with Ar

Abstract The rotational relaxation in the A 2 Δ state of the deuterated methylidyne radical, CD, by Ar is studied. Emission from CD(A 2 Δ ) formed in the ArF laser dissociation of deuterated ketene in the presence of several pressures of Ar was recorded with spectral and time resolution. Analysis of the temporal evolution of the emission led to a set of rotational relaxation rate constants that could be well represented by an exponential gap energy law with two adjustable parameters. The errors associated to the rate constant determination were found to be more important for the low rotational levels. Rate constants for CD(A 2 Δ ) were found to be smaller than the values reported in the literature for the undeuterated methylidyne.

Effects of Laser Irradiation on Artwork Pigments Studied by Laser Ablation and Time-of-Flight Mass Spectrometry

Laser ablation and time-of-flight mass spectrometric analysis of the ablation plume is used to study the different response of several inorganic pigments to laser irradiation. Lead white and lead chromate in pellets and in a binding media are studied. Lead white is compared to azurite, of similar stoichiometry. For lead white the plume composition is rather independent on laser ablation wavelength and does not show important changes after repeated laser beam exposure opposite to that observed for azurite. Ablation of lead white pellets leads to ionized and neutral Pb and PbnOmHx clusters. Much less extent of aggregation in the plume is observed for lead chromate pellets and for the lead pigments in tempera. Similarities can be found between plume composition of ablated lead white and PbO, suggesting that laser/pigment interaction involves formation of PbO, therefore providing indications of the participation of a thermal decomposition mechanism.

X-ray emission by electron impact as a surface characterization tool for the light elements B, C, N and O: sensitivity factors and effective attenuation length

X-ray emission induced by electron impact is a common characterization technique associated to electron microscopy. The possibility of employing this technique for surface and thin film analysis arises from the low energy electrons required to excite the inner shell transitions of the light elements, and is a field not sufficiently explored. In this work, we have studied experimentally the X-ray emission intensities from h-BN, B4C and B2O3 bulk samples to determine the sensitivity factors (also known as k-factors) of the light elements C, N and O relative to B as a function of the incident electron beam energy. Furthermore, evaporated carbon thin films grown on Si(100) with thicknesses in the 20–200 nm range were used to derive the effective attenuation length λ(E) of the technique. In this way, and following a classical surface analysis approach, a fast and simple quantification procedure is presented to determine the composition of any compound of the B–C–N–O family in thin film form. These results have been compared with Monte Carlo simulations.