Diagnostics of lead plasmas produced by laser ablation

The Q-switched Nd:YAG laser operating at its fundamental wavelength (10640 Å), generating pulses of 290 mJ, 7 ns of duration and repeat frequency of 20 Hz, has been used for the ablation of lead targets in vacuum and in ( 6 Torr, 12 Torr and 24 Torr) argon atmosphere. The laser irradiance on the blank was 2x1010 Wcm-2, the diameter of the standard crater was 0.5 mm. In order to study the interaction for lead targets, the characteristics of the plasmas produced-laser were examined in detail with the use of time-resolved technique (200 to 6 000 ns, delay from the laser pulse). The spectrum is observed by using a monochromator with a time resolved optical multichannel analyzer (OMA III), that allowed the detection of each spectrum and its digital recording for later numerical analysis. Spectral lines of Pb I, Pb II, Pb III can be observed and the corresponding most intense transitions of the Ar II. Temperatures and electron number densities were determined from the different plasmas generated and in different conditions. Electron number densities are deduced from the Stark broadening of the line profiles for several lines of Pb I, Pb II and Pb III [1-3]. Electron temperatures of the plasmas were determined from the Boltzmann plot and the Saha-Boltzmann equation. For each spectrum the electron number density, excitation temperature and ionization temperature are calculated for each delay time; we found that the values of the electron density are decreasing from 1017 to 1015 cm-3. The corresponding temperatures were between 25000 to 6000K. A graphical representation of the evolution of temperature and electron number density versus 200 to 6 000 ns delay from the laser pulse is presented. The existence of the local thermodynamic equilibrium (LTE) for each the plasma has been discussed. Also, has been obtained quantitative information on the abundance of the species present in each the plasma

Probabilidades de transición para niveles 2S1/2, 2P1/2,3/2 y 2D3/2,5/2 del átomo de talio

Se han calculado las probabilidades de transición radiativas para 203 líneas que se originan en los niveles ns 2 Si /2, np 2 Pi /2 , 3 /2 y nd 2D3/2 , 5 /2 del átomo TII. Las partes radiales de las funciones de onda se han calculado utilizando un potencial efectivo que incluye los efectos de polarización del "core", efectos relativistas y el tamaño finito del núcleo, considerándose también el efecto de polarización del " core" en el elemento de la matriz de transición. Las vidas medias de los niveles estudiados se han determinado a partir de las probabilidad es de transición calculadas; los valores están en buen acuerdo con los valores experimentales más recientes. También se ha estudiado la variación de la vida media (T) en función del número cuántico principal efectivo (n* ), comprobándose que, para los niveles estudiados, la dependencia entre % y «* tiene la forma x = («* ) m, donde mes del orden de 3. Se muestran los resultados de los cálculos para las probabilidades de transición radiativas y las vidas medias de los estados excitados, y se comparan con los de otros autores, tanto calculados como medidos; el acuerdo es mayoritariamente aceptable, comprobándose la importancia de los efectos relativistas

Application of laser-induced plasma spectroscopy to the measurement of transition probabilities of Ca I

We present improved experimental transition probabilities for the optical Ca I 4s4p-4s4d and 4s4p-4p2multiplets. The values were determined with an absolute uncertainty of 10%. Transition probabilities have been determined by the branching ratios from the measurement of relative line intensities emitted by laser-induced plasma (LIP). The line intensities were obtained with the target (leadcalcium) placed in argon atmosphere at 6 Torr, recorded at a 2.5 µs delay from the laser pulse, which provides appropriate measurement conditions, and analysed between 350.0 and 550.0 nm. They are measured when the plasma reaches local thermodynamic equilibrium (LTE). The plasma is characterized by electron temperature (T) of 11400 K and an electron number density (Ne) of 1.1 x 1016 cm-3. The influence self-absorption has been estimated for every line, and plasma homogeneity has been checked. The values obtained were compared with previous experimental values in the literature. The method for measurement of transition probabilities using laser-induced plasma as spectroscopic source has been checked

Transition probabilities for several u.v. lines of Pb II

Relative transition probabilities for 30 lines arising from excited doublets levels of Pb II have been determined from emission lines intensities in a hollow-cathode discharge. These values were put on an absolute scale by using, where possible, the experimental lifetimes published by other authors. In addition, absolute transition probabilities were obtained by using line-strength sum rules and the results were found to be in agreement with data derived from lifetime measurements. Our experimental results are compared with experimental and theoretical data given by other authors

Calculation of the Stark widhs and Shifts for several lines of the thallium atom

Stark widths and shifts for eight lines of Tl I, arising from the np 2P01/2, 3/2 (n = 7−9) and 7s 2S1/2 levels have been calculated using semiempirical formulas, and compared with those obtained by other author

Experimental transition probabilities for several spectral lines arising from the 5d10 6s{8s, 7p, 5f, 5g} electronic configurations of Pb III

Transition probabilities for 30 spectral lines, arising from the 5d10 6s{8s, 7p, 5f, 5g} electronic configurations of Pb III (20 measured for the first time), have been experimentally determined from measurements of emission line intensities in a plasma lead induced by ablation with a Nd:YAG laser. The line intensities were obtained with the target placed in molecular argon at 6 Torr, recorded at a 400 ns delay from the laser pulse, which provides appropriate measurement conditions, and analysed between 200 and 700 nm. They are measured when the plasma reaches local thermodynamic equilibrium (LTE). The plasma under study had an electron temperature (T) of 21,400 K and an electron number density (Ne) of 7×1016 cm−3. The influence of self-absorption has been estimated for every line, and plasma homogeneity has been checked. The values obtained were compared with previous experimental values and theoretical estimates where possible

A theoretical study of transition probabilities and lifetimes for the Sn III: core polarization effects

Data on atomic properties are not only relevant to spectroscopy, but these values are of interest in a variety of other fields in physics and technology. In this work we present a completer study of Sn III transition probabilities and lifetimes of spectral lines arising from 4d105sns (n=6-9) and 4d105snp (n=5-6) configurations These values were obtained in intermediate coupling (IC) and using relativistic Hartree-Fock calculations including core-polarization effects following the suggestions of Migdalek et al. [1]. We use for the IC calculations the standard method of least square fitting from experimental energy levels by means of Cowan [2] computer code. For the calculations we used all the experimental levels present in the Moore table. Transition probabilities and lifetimes are generally in good agreement with the experimental data [3, 4, 5]. In the next Table we present some values as example

Theoretical Stark broadening parameters of Pb V spectral lines

In this paper, we report calculated values of the Stark widths and shifts for 72 spectral lines of Pb v. They were calculated using the Griem semi-empirical approach. A set of wavefunctions obtained from Hartree–Fock relativistic calculations including core polarization effects was used. Stark widths and shifts corresponding to lines arising from 5d9ns (n = 7, 8), 5d9 6p, 5d9 6d and 5d9 5f configurations of Pb v. Stark widths and shifts are presented for an electron density of 1017 cm−3 and temperatures T = 1.6–5.0 (104 K). The 2142.5, 2167.9 and 2278.6 Å lines of Pb v recently measured are included in our calculations. In this case, we have included for comparison calculations without core polarization effects. There is good agreement between our calculations and the above-cited experimental values

Stark Broadening of Sn III Spectral Lines of Astrophysical Interest: Predictions and Regularities

The determination of the Stark broadening parameters of Sn ions is useful for astrophysicists interested in the determination of the density of electrons in stellar atmospheres. In this paper, we report on the calculated values of the Stark broadening parameters for 171 lines of Sn iii arising from 4d105sns (n= 6–9), 4d105snp (n= 5, 6), 4d105p2, 4d105snd (n= 5–7), 4d105s4f and 4d105s5g. Stark linewidths and line shifts are presented for an electron density of 1023 m−3 and temperatures T= 11 000–75 000 K. These have been calculated using a semi-empirical approach, with a set of wavefunctions obtained from Hartree–Fock relativistic calculations, including core polarization effects. The results obtained have been compared with available experimental data. These can be used to consider the influence of Stark broadening effects in A-type stellar atmosphere

Core-polarization Effects for the Stark Broadening of Pb III Spectral Lines: Predictions and Regularities

Using a semi-classical approach, we have calculated values of the Stark broadening parameters for several lines of Pb III. Stark widths and shifts are presented for an electron density of 1017 cm¿ 3 and temperatures T = 11000-100000 K. In this work, we have carried out a study of the influence of the introduction of the terms that allow us to take into account the Core Polarization (CP) effects in the calculation of the Stark broadening parameters. Our results are compared with available experimental and theoretical data. Common trends for the several lines have been found and are discussed