Electron impact excitation cross section calculations of the fine structure transitions of Mo and their applications in the diagnostics of the laser induced Mo plasma

Abstract

The current work reports a detailed calculation of electron impact excitation cross sections for the fine structure transitions of Mo from the manifolds 4d55s, 4d45s2, 4d6, and 4d55p to the manifolds 4d55s, 4d45s2, 4d6, 4d55p, 4d45s5p, 4d55d, 4d56s, 4d45s6s and 4d57s, using the Relativistic Distorted Wave (RDW) approximation for plasma modeling application. Multi-configuration Dirac Fock wave functions are used in the calculations. The oscillator strength and cross-section results are compared with the previous calculations and measurements. A comprehensive collisional radiative (CR) model is developed to characterize laser-induced Molybdenum plasma to ensure that the calculated cross-section can be used for various plasma modeling applications. The current CR model has taken into account the electron impact excitation and de-excitation processes using the calculated consistent cross-sections. The electron-induced processes are dominant kinetic processes in the laser-induced plasma. Furthermore, the diagnostics of the laser-induced Mo plasma is done by coupling the current CR model with the experimental laser-induced breakdown spectroscopic measurements of Mal et al. (Appl. Phys. B 127, 52 (2021)). The plasma parameter, i.e., electron temperature, has been calculated using nine measured intensities of the emission lines of Mo, with wavelengths 406.9, 423.2, 438.1, 453.6, 476.0, 550.6, 553.3, 557.0 and 592.8 nm. The results are also compared with the values reported from the Boltzmann plot at various delay times ranging from 0.5 to 5.0 µs.

Fine structure resolved excitation cross sections of singly ionized Ga for the modeling and diagnostics of Ga plasmas

“…While acknowledging that non-perturbative methods like Convergent Close Coupling (CCC) and B-spline R-Matrix (BSR) may offer enhanced accuracy in the low energy threshold regime, our extensive work in numerous atomic systems attests to the success of our RDW method employing a multi-configurational wavefunction approach. This method has consistently yielded reliable data for plasma modeling applications in the past [17][18][19]. Furthermore, it is acknowledged that cross sections from non-perturbative approaches are often limited and predominantly available in the low energy domain.…”

Relativistic calculation of electron impact excitation of tin: cross sections of importance in plasma modeling

“…However, even a minor deviation from the LTE condition can significantly affect the accuracy of the OES results and hence the plasma diagnostics. Thus, OES measurements will only give accurate results when coupled with appropriate population-kinetic models such as collisional radiative (CR) models [12]. These models solve a coupled rate balance equation for the excited state population of the plasma which requires vast atomic and molecular data such as transition energies, oscillator strengths, transition probabilities, and cross sections for various atomic and molecular processes inside the plasma.…”

“…Since electron collisions with tin are one of the most dominant processes in LIPs and fusion plasmas, the requirement of EIE cross section data is in high demand. Recently, our group reported the relativistic EIE cross sections for Mo and successfully implemented them in a collisional radiative model for the diagnostics of the LIP of Mo [12].…”