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A collisional radiative model for Kr III in the ultraviolet regime is developed. For this purpose, atomic parameters for 4s24p4, 4s4p5, 4s24p3nl, and 4s24p35d configurations with n ranging from 5 to 7 and l=s,p, using the multiconfiguration Dirac–Hatree–Fock method are calculated. The effects of Breit and radiative quantum electrodynamic corrections are also included. Electron impact excitation cross-sections from the ground state, along with four metastable states arising from the 4s24p4 configuration to all fine structure levels of interest, are calculated using the relativistic distorted wave method. The reliability of the model is tested by comparing the predicted results with the previous measurements.

Collisional-radiative models are commonly used to analyse atomic and molecular processes in low temperature plasmas by determining the distribution functions of excited states as functions of various plasma parameters. This paper outlines the improvements to a zero-dimensional collisional-radiative model, developed at Keio University, for purposes relevant to the analysis of emission measurements in low temperature hydrogen plasmas. The extension of this 0D model centres on the inclusion of additional molecular species and reactions, a calculation of emission intensity in order to directly compare with experimental work, and the addition of a simple wall model to allow for a deeper understanding of recycling of atoms and molecules in low temperature plasmas close to plasma facing components in fusion machines. Results from the improved model are then compared with both an existing CR model for benchmarking and experimental emission spectroscopy data from an inductively-coupled plasma device at the University of Liverpool. These results show how the developments to the model have increased the relevance to experimental plasmas, such as those in the power exhaust regions of fusion machines, with the ratio of the Hβ/Hα line intensities outputted from the improved CR model mirroring more closely the emission measured experimentally in the ICP device.

The interplay of kinetic electron physics and atomic processes in ultrashort laser-plasma interactions provides a comprehensive understanding of the impact of the electron energy distribution on plasma properties. Notably, nonequilibrium electrons play a vital role in collisional ionization, influencing ionization degrees and spectra. This paper introduces a computational model that integrates the physics of kinetic electrons and atomic processes, utilizing a Boltzmann equation for nonequilibrium electrons and a collisional-radiative model for atomic state populations. The model is used to investigate the influence of nonequilibrium electrons on collisional ionization rates and its effect on the population distribution, as observed in a widely known experiment [Young et al., Nature (London) 466, 56 (2010)0028-083610.1038/nature09177]. The study reveals a significant nonequilibrium electron presence during XFEL-matter interactions, profoundly affecting collisional ionization rates in the gas plasma, thereby necessitating careful consideration of the Collisional-Radiative model applied to such systems.

We present a simplified version of an average-atom collisional-radiative model employing both local-thermodynamic-equilibrium average-atom and isolated-ion atomic data. The simplifications introduced do not lead to any substantial errors, and they significantly speed up calculations compared with the basic average-atom model involving direct solution of the self-consistent-field equations. Average ion charges, charge state distributions, and emission spectra of non-local-thermodynamic-equilibrium (NLTE) gold plasmas calculated using various modifications of the average-atom collisional-radiative model are compared with those obtained using the THERMOS model with the detailed configuration accounting approach. We also propose an efficient method to calculate thermodynamic functions of NLTE plasmas in the context of the simplified average-atom collisional-radiative model.

In this study, eight emission lines in the visible wavelength range of neutral helium were used to diagnose the electron density and temperature of the Large Helical Device (LHD) helium plasma instead of the conventional three-line method. The collisional-radiative (CR) model for low-pressure helium plasma was revised to include the optical escape factors for spontaneous transition from the n1P states to the ground state so that the influence of the absorption effect under optically thick conditions could be considered. The developed algorithm was based on fitting the number densities of eight excited states obtained using optical emission spectroscopy (OES). The electron density, electron temperature, ground-state density, and optical escape factors were selected as the fitting parameters. The objective function was set as the summation of the residual errors between the number densities measured in the experiment and those calculated using the revised model. A regularization term was introduced for the optical escape factor and optimized through bias and variance analyses. The results show that the agreement between the number density calculated by the algorithm and its counterpart measured in the experiment was generally improved compared to the method using three lines.

This paper describes the use of Optical Emission Spectroscopy (OES) to measure electron densities and temperatures in non-equilibrium plasmas. The ways to interpret relative line-intensities of neutral argon atoms are evaluated based upon a collisional-radiative model including atomic collisional processes. A conversion from an excitation temperature determined from relative line intensities assuming a Boltzmann population distribution to the thermal electron temperature in the electron temperature range 1–4 eV and electron density range 1010–1012 cm–3 is given. Procedures to obtain electron temperature Te and density Ne of non-equilibrium argon plasma by OES measurement with collisional radiative model.

Plasmas of a variety of types can be described by the collisional radiative (CR) model developed by Colombant and Tonan. From the CR model, the ion distribution of a plasma at a given electron temperature and density can be found. This information is useful for further simulations, and due to this, the employment of a suitable CR model is important. Specifically, ionization bottlenecks, where there are enhanced populations of certain charge states, can be seen in these ion distributions, which in some applications are important in maintaining large amounts of a specific ion. The present work was done by implementing an accepted CR model, proposed by Colombant and Tonon, in Python and investigating the effects of variations in the ionization energy and outermost electron subshell occupancy term on the positions of ionization bottlenecks. Laser Produced Plasmas created using a Nd:YAG laser with an electron density of ∼ne = 1021 cm−3 were the focus of this work. Plots of the collisional ionization, radiative recombination, and three-body recombination rate coefficients as well as the ion distribution and peak fractional ion population for various elements were examined. From these results, it is evident that using ionization energies from the NIST database and removing the orbital occupancy term in the CR model produced results with ionization bottlenecks in expected locations.

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It is crucial to measure the electron density (ne) and temperature (Te) for applications such as developing small helicon sources in plasma thrusters. Hence, this study developed a method based on an optical emission spectroscopic (OES) measurement without disturbance or contamination for helicon plasma produced using argon gas. The argon collisional-radiative (CR) model was used to describe the excitation number density in plasma as a function of ne and Te. Each number density ratio was surveyed as a function of ne and Te. From these results, contours of two number densities, i.e., two excitation energy levels, were drawn on an ne–Te plane. By applying various contour pairs, ne and Te were determined from the intersection point of two contours whose values were taken from the experimental intensities. Finally, we compared the new OES measurements with the CR model for various intensity ratios and found a way to select a valid intensity ratio that is in good agreement with the ne and Te derived by the probe method.

Energy levels, transition probabilities, collision sections, and collision excitation rate coefficients of NII ion have been calculated using Flexible Atomic Code, which is based on the multiconfiguration Dirac–Fock method. The ratios of line intensity, I567.96 nm/I500.52 nm, where the 567.96 and 500.52 nm are two strong spectral lines from the core current channel of lightning, have been calculated by using the collisional-radiative model, in which the line intensity is proportional to the collision excitation rate coefficients from the ground state to the excited state and the transition probability from the high excited state to the low excited state. The temperatures of six lightning plasma channels were then obtained, and they are consistent with temperatures obtained by diagnosing the actual spectrum with the multispectral line method. [ABSTRACT FROM AUTHOR]

A collisional radiative (CR) model has been developed for the diagnostics of Ne–Ar mixture plasma. The 40 fine‐structure resolved energy levels of neon corresponding 2p53s, 2p53p, 2p53d, 2p54s, and 2p54p along with ground state (2p6) and ion state (2p5) have been considered. All the essential population and de‐population channels viz. electron impact excitation‐de‐excitation, ionization, two/three‐body recombination, radiative decay, self‐absorption correction, diffusion, etc., have been considered in the model. The quenching of relatively higher lifetime states 2p53s due to interaction with Ar atoms through associative and Penning ionization is also included in the model. The applicability of the CR model is demonstrated by performing the optical diagnostic of rf induced inductively coupled Ne–Ar mixture plasma. The plasma parameters viz. electron temperature, electron density, and population distribution of levels at various mixture conditions are extracted by coupling the present CR model predictions with emission and absorption measurements by Boffard et al. [J. Phys. D: Appl. Phys., 45, 382001 (2012) and private communication]. The results are also compared with earlier optical models and Langmuir probe measurements. The self‐absorption correction (escape) factors and electron impact excitation rates at various Ne–Ar mixture concentrations are also presented. [ABSTRACT FROM AUTHOR]