A collisional-radiative (CR) model for low-temperature Ne plasma is developed. Various radiative and collisional processes involving the ground 2p 6 and the excited 2p 5 3s, 2p 5 3p, 2p 5 3d, 2p 5 4s and 2p 5 4p states are considered in the plasma. First, we calculate a complete set of required electron-impact excitation cross-sections of Ne, which is an important process in such low-temperature plasma. We used the relativistic distorted wave (RDW) theory and calculated electron excitation cross-sections for the transitions from the ground 2p 6 state to the excited 2p 5 3s, 2p 5 3p, 2p 5 3d, 2p 5 4s and 2p 5 4p states, as well as from the excited state 2p 5 3s to the 2p 5 3p and 2p 5 4p excited states of the Ne atom in a wide range of incident electron energies from the threshold to 500 eV. The ground and different excited states of the Ne are represented through the multiconfiguration Dirac-Fock wave functions, which are obtained using the GRASP2K code. To ascertain the reliability of the obtained wave functions, we calculated the oscillator strengths for different dipole allowed transitions, and compared them with the available experimental and theoretical results. Further, the calculated detailed RDW cross-sections are presented and compared with the available experimental and other theoretically calculated values. The cross-sections for 2p 5 3s to 2p 5 4p and 2p 5 3s (J=1 only) to 2p 5 3p are reported for the first time. The complete set of calculated electron excitation cross-sections of different transitions of Ne along with other processes are used to develop the CR model. The model has been applied to the diagnostics of low-temperature Ne plasma by coupling it to the optical emission and absorption measurements of Boffard et al (2012 J. Phys. D: Appl. Phys. 45 382001, and 2009 Plasma Sources Sci. Technol. 18 035017). The extracted values of electron density, electron temperature and the calculated 1s i level populations have been compared with the corresponding measurements available in the pressure range of 5-25 mTorr and are found to be in excellent agreement.

A detailed fine-structure resolved collisional radiative model is developed to investigate the laser-produced Mg plasma. The dominant processes linked with the electron impact excitation and de-excitation have been considered explicitly in a very reliable and consistent manner in the present model. The required electron impact excitation cross-sections of Mg for the large number of transitions from the ground state 3s2 (J = 0) to the 3s3p, 3s4s, 3s3d, 3s4p, 3s5s, 3s4d, 3s5p, 3s6s, 3s5d, and 3s6p excited states and from 3s3p manifolds to the other fine-structure levels of 3s4s, 3s3d, 3s5s, 3s4d, 3s6s, and 3s5d configurations are obtained using the fully relativistic distorted wave approach. To ensure the accuracy of our calculations, where available, the oscillator strengths and cross-sections are compared with previous measurements and other calculations. Further, plasma diagnostics are carried out by coupling the present collisional radiative model with the laser-induced breakdown spectroscopy measurements reported by Delserieys et al (2009 J. Appl. Phys., 106, 083304). Five measured intense emission lines of Mg viz 383.3, 470.3, 517.8, 552.8, and 571.1 nm are used and corrected through the self-absorption to extract the plasma parameters i.e. electron temperature and electron density. The obtained plasma parameters at different delay times ranging from 100–700 ns are compared with the results of Delserieys et al (2009 J. Appl. Phys., 106, 083304) that were estimated using the Thomson scattering and Boltzmann plot approaches.

We report the fine structure resolved electron impact excitation cross-sections of Si+2 from its ground state 3s2 (J = 0) to the 41 excited fine structure levels of the configurations 3s3p, 3p2, 3s3d, 3s4s, 3s4p, 3s5s, 3s4d, 3s4f, 3s5p, 3s5d and 3s5f using relativistic distorted wave theory. The excitation cross-sections from excited metastable levels (3P0,3P2) of the configuration 3s3p to higher excited levels as well as for some other dominant transitions relevant to plasma modeling are also obtained. In addition, the ionization cross-sections are evaluated from the ground and metastable levels to higher ionized state Si+3 (2S1/2). The calculated cross-sections are utilized to obtain the rate coefficients corresponding to electron impact excitation and ionization processes affecting the intensity of prominent Si+2 emission lines 379.61, 380.65, 456.78, and 457.48 nm recorded through optical emission spectroscopic measurements by Wang et al. (Phys. Plasmas 27, 063513 (2020)) on laser produced silicon plasma. Further, the rate coefficients corresponding to radiative, and three body recombination are also presented. The reported cross-sections and rate coefficients will be useful to develop rigorous collisional radiative model for the diagnostics of silicon plasma.

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We have performed the non-invasive diagnostic study of capacitively coupled Ne-O2/H2 mixture plasma through the Optical emission spectroscopy (OES) coupled with a suitable Collisional Radiative (CR) model. Capacitively coupled neon radio-frequency (rf) discharge (flowing downstream) with small admixture of O2/H2 have been generated in a vacuum chamber using 13.56 MHz rf signal and 120 W power supply. Keeping O2 and H2 flow rates fixed at 0.01 and 0.015 LPM respectively, the neon flow rate has been varied as 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 LPM to obtain different mixture concentration of Ne-O2 and Ne-H2 discharge. The pressure in the chamber has been observed in intermediate range (~500-25000 Pa) for different mixture concentrations. Optical emission spectroscopy (OES) measurements are recorded at various operating conditions in the wavelength range from 200 nm to 1200 nm. To extract the information of plasma parameters from the OES measurements, a comprehensive fine-structure resolved collisional radiative (CR) model has been developed. In the diagnostic process, five intense Ne-I emission lines at 594.48, 607.43, 633.44, 638.30, 703.24 nm are used. The CR model considers all the important processes i.e. electron impact excitation, electron impact de-excitation, radiative decay, ionization, two-three body recombination, and diffusion. The quenching process of 1s (1s5,1s4,1s3) levels of neon by the O2/H2 molecule has been included in the model. Radiative transitions from the upper levels to the ground state (1S0) and to the 1s levels of neon are corrected for self-absorption. The electron temperature (Te) and electron density (ne) of the plasma have been extracted for all the mixture concentrations of Ne-O2 and Ne-H2. With the different mixture concentrations of O2/H2 in neon discharge, the variation of population of metastable levels (1s5, 1s3) of neon and intensities of 656.28 nm of hydrogen and 777.4 nm of oxygen lines have been reported and discussed.