This review covers developments in ‘Atomic Spectrometry’. It covers atomic emission, absorption, fluorescence and mass spectrometry, but excludes material on speciation and coupled techniques which is included in a separate review. It should be read in conjunction with the other related reviews in the series.1–6 A critical approach to the selection of material has been adopted, with only novel developments in instrumentation, techniques and methodology being included. Developments worthy of note include photochemical and electrochemical methods of vapour generation, single particle analysis using ICP-MS and the development of new methods for direct plasma generation in liquid samples. The use of MC-ICP-MS continues to grow in importance for isotope ratio measurements in fields as diverse as geochronology, nuclear forensics and biomedical research. Laser-based methods are also important in many fields, particularly for direct and stand-off analysis of solid samples.

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Atomic spectrometry update: review of advances in atomic spectrometry and related techniques

We present a nearly complete rapid neutron-capture process (r-process) chemical inventory of the metal-poor ([Fe/H] = −1.46 ± 0.10) r-process-enhanced ([Eu/Fe] = +1.32 ± 0.08) halo star HD 222925. This abundance set is the most complete for any object beyond the solar system, with a total of 63 metals detected and seven with upper limits. It comprises 42 elements from 31 ≤ Z ≤ 90, including elements rarely detected in r-process-enhanced stars, such as Ga, Ge, As, Se, Cd, In, Sn, Sb, Te, W, Re, Os, Ir, Pt, and Au. We derive these abundances from an analysis of 404 absorption lines in ultraviolet spectra collected using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope and previously analyzed optical spectra. A series of appendices discusses the atomic data and quality of fits for these lines. The r-process elements from Ba to Pb, including all elements at the third r-process peak, exhibit remarkable agreement with the solar r-process residuals, with a standard deviation of the differences of only 0.08 dex (17%). In contrast, deviations among the lighter elements from Ga to Te span nearly 1.4 dex, and they show distinct trends from Ga to Se, Nb through Cd, and In through Te. The r-process contribution to Ga, Ge, and As is small, and Se is the lightest element whose production is dominated by the r-process. The lanthanide fraction, log X La = −1.39 ± 0.09, is typical for r-process-enhanced stars and higher than that of the kilonova from the GW170817 neutron-star merger event. We advocate adopting this pattern as an alternative to the solar r-process-element residuals when confronting future theoretical models of heavy-element nucleosynthesis with observations.

https://iopscience.iop.org/article/10.3847/1538-4365/ac5cbc/pdf

The R-process Alliance: A Nearly Complete R-process Abundance Template Derived from Ultraviolet Spectroscopy of the R-process-enhanced Metal-poor Star HD 222925

In this article, we compare two analytical methods that have been recently proposed: the columnar density Saha–Boltzmann plot method of Cristoforetti and Tognoni (Cristoforetti, G.; Tognoni, E. Spe...

Exploiting Self-Absorption for Plasma Characterization in Laser-Induced Breakdown Spectroscopy Experiments: A Comparison of Two Recent Approaches.

In this review, we report and critically discuss the application of LIBS for the determination of plasma-emission fundamental parameters, such as transition probabilities, oscillator strengths, Stark broadening and shifts, of the emission lines in the spectrum. The knowledge of these parameters is of paramount importance for plasma diagnostics or for quantitative analysis using calibration-free LIBS methods. In the first part, the theoretical basis of the analysis is laid down; in the second part, the main experimental and analytical approaches for the determination by LIBS of the spectral line spectroscopic parameters are presented. In the conclusion, the future perspectives of this kind of analysis are discussed.

https://www.mdpi.com/2076-3417/10/14/4973/pdf

Laser-Induced Breakdown Spectroscopy for Determination of Spectral Fundamental Parameters

Measurement of neutral gadolinium oscillator strengths using dual-comb absorption spectroscopy in laser-produced plasmas

In this article, 112 oscillator strengths from Mo II have been measured, 79 of which for the first time. The radiative parameters have been obtained by laser-induced breakdown spectroscopy (LIBS). The plasma is produced from a fused glass sample prepared from molybdenum oxide with a Mo atomic concentration of 0.1%. The plasma evolved in air at atmospheric pressure, and measurements were carried out with the following plasma parameters: an electron density of cm−3 and an electron temperature of K. In these conditions, a local thermodynamic equilibrium environment and an optically thin plasma were confirmed for the measurements. The relative intensities were placed on an absolute scale by combining branching fractions with the measured lifetimes and by comparing well-known lines using the plasma temperature. Comparisons were made to previously obtained experimental and theoretical values wherever possible.

Measured oscillator strengths in singly ionized molybdenum

Experimental transition probabilities for 37 spectral lines of Re II (15 measured for the first time) have been obtained from a plasma produced by ablation of a Zn?Re alloy with a Nd:YAG laser. The plasma evolved in air at atmospheric pressure, and measurements were performed for the following plasma parameters: an electron density of (1.27 ? 0.19) ? 1017 cm?3 and an electron temperature of 11?200 ? 400 K. The relative intensities were placed on an absolute scale by the combining branching fractions with the measured lifetimes and by comparing well-known lines using the plasma temperature. Some plasma parameters, such as the temperature and the electron density, were also obtained to provide a local thermodynamic equilibrium environment and an optically thin plasma. Comparisons were made to previously obtained experimental and theoretical values wherever possible.

Experimental transition probabilities for spectral lines of Re II

Measurements of 161 oscillator strengths arising from highly excited levels of Mo II are presented, 148 of which are obtained for the first time. These results extend the previous ones already published on lower excited levels of Mo II. A laser-induced plasma generated from a fused glass sample prepared from molybdenum oxide with a Mo atomic concentration of 0.1% was used to obtain the presented radiative parameters via laser-induced breakdown spectroscopy. Measurements were carried out with an electron density of (2.5 ± 0.1) 1017 cm−3 and an electron temperature of 14 400 ± 200 K as the plasma evolved in air at atmospheric pressure. As a consequence, an optically thin plasma and a local thermodynamic equilibrium environment were then present in the measurements. In order to put on an absolute scale the relative intensities, both the combination of branching fractions with measured lifetimes and the comparison of well-known lines using the plasma temperature were carried out. Also, the new results are compared with previously theoretical and obtained experimental values wherever possible.

R Mayo-García

Papers

Measured oscillator strengths in singly ionized molybdenum

Experimental transition probabilities for spectral lines of Re II

Experimental oscillator strengths of highly excited levels of Mo II