Electron impact cross-sections and rate coefficients of Si⁺² ions relevant to collisional radiative modeling of silicon plasma

Abstract

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.

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

“…In contrast, for the J = 0 → 1 transition, the final level has an even parity with an odd angular momentum, causing the direct T-matrix term to be zero. A similar trend is also observed in the recent studies by Umer et al [29] and Baghel et al [30]. Umer et al [29] reported the relativistic convergent close coupling (RCCC) calculations for the cross sections of the excitation from 5s 2 → 5s6s for Sn 2+ .…”

“…Consequently, the direct T-matrix element for this transition vanishes, in contrast to the other transitions (with even J f and even parity), resulting in a more rapid decrease in the cross section as the incident electron energy increases. A similar behavior is also observed in the RCCC calculations of the excitation cross sections for 5s 2 → 5p 2 for Sn 2+ of Umer et al [29], and the RDW calculations of excitation cross sections for 3s 2 → 3p 2 for Si 2+ of Baghel et al [30].…”

“…It is worth highlighting that the cross section corresponding to the excitation to the 1 D 2 state is the largest and decreases slowly as the projectile energy increases, unlike the cross sections for the other J f = 2 state, which decreases faster. A consistent pattern is evident in both the RCCC calculations of Umer et al [29] for the excitation cross sections for Sn 2+ , specifically for the 5s 2 → 5s5d transitions, as well as the RDW calculations of Baghel et al [30] for the excitation cross sections for Si 2+ in various transitions, including 3s 2 → 3s3d, 3s 2 → 3s4d, and 3s 2 → 3s5d.…”

“…Umer et al [29] reported the relativistic convergent close coupling (RCCC) calculations for the cross sections of the excitation from 5s 2 → 5s6s for Sn 2+ . Whereas, Baghel et al [30] reported the excitation cross sections using the RDW method for 3s 2 → 3s4s and 3s 2 → 3s5s for Si 2+ . The ground states in both these cases correspond to a closed shell configuration with both even parity and even angular momentum, i.e.…”