G. H. Cavalcanti

Determination of plasma temperature by a semi-empirical method

Doppler or Stark line broadening effects are generally used to determinate plasma temperature. These methods are difficult to apply to spectra of highly ionized atoms due to the short wavelengths involved. It is not at all easy to achieve sufficient wavelength resolution in this spectral range. In this case, a spectroscopic technique based on the relative intensities of lines must be used to measure the electron temperature in a plasma. However the relation of the measure of relative line intensity and the plasma electron temperature is complex and a number of issues must be examined for the diagnostic. In simple cases, only a two levels system need be considered. Here we introduce a semi-empirical method to determine the plasma temperature that takes into account multiple levels structure. In the theoretical model we consider a local thermodynamic equilibrium(LTE). The greatest difficult in the determination of plasma temperature using a multiple levels approach is overcome by calculating the transition probabilities in terms of the oscillator strength parameters. To check the method we calculated the oscillator strengths for the Cu I using a multi-configurational Hartree-Fock relativistic (HFR) approach. The electrostatic parameters were optimized by a least-squares procedure, in order to obtain the best fitting to the experimental energy levels. This method produces gf- values that are in better agreement with their experimental values than the produced by the ab initio calculation. The temperature obtained was 5739.3 K, what is compatible with direct measurements made for cupper DC discharge.

Recovery of archaeological wall paintings using novel multispectral imaging approaches

New approaches in the application of multispectral imaging to the recovery of archeological wall paintings are presented, based on statistical techniques and on a novel method of image treatment (Chromatic Derivative Imaging – ChromaDI) which offers a way of embedding information coming from four spectral bands into a standard RGB image. The methods are applied to some wall paintings from the Tomb of the Monkey, an Etruscan tomb in the necropolis of Poggio Renzo, near the city of Chiusi (Siena), Italy, dated around 480-470 BC. It is shown that the techniques described are able to highlight and enhance a number of details that cannot be perceived in either any of the original channel images or any single processed output channel.

A theta-pinch as a spectroscopic light source

The aim of this work is to describe a theta-pinch for spectroscopic studies. This machine is different in some aspects from its equivalent for fusion studies. Here, in a single experiment, 1000 shots are used normally. The capacitor bank stores 14 kJ of electrical energy at 60 kV, but only 1 kJ is necessary to obtain an electron peak temperature of 150 eV, which is enough to produce a good emission spectrum in the VUV range of 300 to 2000 ?. With this device it is possible to obtain intermediate ionization states of many elements (ionized six or seven times). Similarly to tokamaks, the theta-pinch spectrum contains spectral lines due to forbidden transitions, where the rule for dipole electric transition is violated.

X-Ray Fluorescence Analysis of XII–XIV Century Italian Gold Coins

An extensive analytical study has been performed on a large number of gold coins (Norman-Swabian Augustale and Tari, Grosso of Lucca, Florin of Florence) minted in Italy from the end of XII century to XIV century. The X-ray fluorescence (XRF) technique was used for verifying the composition of the coins. XRF is a nondestructive technique particularly suited for in situ quantitative analysis of gold and minor elements in the precious alloy. The Florins turned out to have a gold content very close to 24 carats (pure gold) although in a couple of cases we observed relatively high concentrations of iron (around 2%) or lead (around 1%). The Grosso of Lucca has a similar composition, with a measured gold content around 97% due to a higher silver percentage (about 2%), with respect to the average Florin. The Augustali analyzed showed, on average, a gold content around 89%. The average gold content of the Tari analysed is around 72%, with a relatively large variability. The analysis revealed the use of native gold for the coinage of the Florins, excluding the possibility of recycling gold coming from other sources. On the other hand, the variability observed in the compositions of the Tari and Augustali could suggest the reuse of Islamic and North African gold. The study could shed some light on the sudden diffusion of gold coins in Italy around the first half of XIII century, allowing hypotheses on the provenience of the gold used for a coinage that dominated the economic trades from then on.

Weighted oscillator strengths and lifetimes for the Ar III spectrum

Abstract The weighted oscillator strengths (gf ) and the lifetimes for Ar III presented in this work were carried out in a multiconfiguration Hartree–Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetimes values that are closer to the experimental ones. In this work we presented all the experimentally known electric dipole Ar III spectral lines.

Applications of LIBS to the Analysis of Metals

In this chapter we will discuss the basic theoretical principles of the laser ablation process on metal alloys, and will present successful applications of the LIBS technique to the analysis of such materials (aluminium alloys, iron based alloys, copper based alloy, precious alloys, and others). A special emphasis will be given to analytical applications of LIBS performed in line and/or in situ.

Weighted oscillator strengths and lifetimes for the SVII spectrum

The weighted oscillator strengths (gf) and the lifetimes presented in this work were carried out in a multiconfiguration Hartree-Fock relativistic approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work, we presented all the experimentally known electric dipole S VII spectral lines.

Double and Multiple Pulse LIBS Techniques

This chapter will introduce the physical principles underlying double and multiple pulse LIBS analysis and the main applications of this technique for stand-off analysis of hazardous materials, for environmental analysis, for the analysis of biological materials and for cultural heritage and archaeological studies. The available commercial instrumentation for double pulse LIBS analysis will also be presented and discussed.

Weighted oscillator strengths and lifetimes for the S IX and S X spectra

Abstract The weighted oscillator strengths ( gf ) and the lifetimes presented in this work were carried out in a multi configuration Hartree–Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf -values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work, we presented all the experimentally known electric dipole S IX and S X spectral lines.

Weighted oscillator strengths and lifetimes for the neutral oxygen spectrum, O I

The weighted oscillator strengths (gf) and the lifetimes for O I presented in this work were obtained in a multiconfiguration Hartree-Fock relativistic (HFR) approach. In this calculation, the electro-static parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work we present all the experimentally known electric dipole atomic transitions and energy levels for the O I spectrum.