Theoretical investigation of iodine plasma through detailed electron impact excitation cross-section calculations and collisional-radiative model analysis

In the present study, we consider the electron impact excitation of neutral iodine and its application in developing a collisional-radiative model for plasma diagnostics of iodine plasma. Electron impact excitation cross-sections are calculated using fully relativistic distorted wave theory. The required atomic structure calculations for iodine are carried out using the relativistic multi-configuration Dirac-Fock method. The excitation energies obtained are reported and compared with values from the NIST database. The electron impact excitation cross-sections are calculated from the ground (5p(5) P-2(3/2)degrees) and first-excited state (5p(5) P-2(1/2)degrees) to the several upper fine structure levels. Our cross-section results align well with previous studies, reported by Ambalampitiya et al (2021 Atoms 9 103) using the Breit-Pauli B-spline R-matrix method. Further, calculated cross-section results are incorporated into the collisional-radiative model. Our model also includes electron impact ionization, de-excitation, three-body recombination, and radiative decay. We validate our model using emission spectra from inductively coupled iodine plasma. For this purpose, we used the recorded intensities for the emission lines, 486.23 nm, 511.92 nm, 523.45 nm, 589.40 nm, and 608.24 nm are compared with those obtained from our model to calculate electron temperature and electron density of the iodine plasma.