Spectral line broadening is calculated based on a microscopic quantum statistical approach. By using thermodynamic Green's function, plasma correlation effect, electrostatic and dynamic screening, and perturber-radiator interaction are taken into account. Ions are treated in quasistatic approximation due to Stark effect. The line broadening for 6678？？ (21P-31D) and 5016？？ (21S-31P) transitions of neutral helium is calculated in the electron density range and temperature range , and the density and temperature dependence of the line width are investigated. A good agreement is shown by comparing the calculated values with the existing experimental and theoretical data. 1. Introduction Optical spectroscopy is one of the most important diagnostic tools to characterize warm and dense plasmas. The emitted radiation from a plasma is perturbed by interaction between a radiating atom and surrounding particles, which leads to spectral line broadening; the most effective mechanism is Stark broadening (pressure broadening). Line profile calculation is an interesting technique to determine the internal plasma parameters, such as density, temperature, and composition, to study the microscopic processes within plasma, and to check the quality of the predicted parameters [1, 2]. Several semiclassical and quantum-mechanical approaches have been investigated to calculate spectral line shapes in plasmas [1, 3–16]. Helium lines were calculated by Griem et al. [1, 3] in a semiclassical approach, the so-called standard theory (ST), using an impact approximation for electrons with a cut-off procedure, while ions were treated in a quasistatic approximation due to the static microfield of perturbers. The electron broadening impact parameters are calculated for neutral helium lines by using semiclassical perturbation formalisms based on the approach developed by Sahal-Bréchot [4, 5]. Furthermore, the convergent theory was improved by Bassalo et al. [6] in a many-level approximation to calculate the Stark broadening parameters of neutral helium lines. Recently, molecular dynamics (MD) simulations have been performed by Calisti et al. [17] and Gigosos et al. [18, 19] by including the time sequence of the microfield distribution as a random process. The quantum-mechanical Green's function method is considered in this paper to calculate the He I spectral lines in dense plasmas, assuming local thermal equilibrium (LTE) [20–26]. Spectral line profiles of helium are important in plasma diagnostic. Some of the lines are measured in a pulsed arc plasma by Pérez et al. [27–29], studied in
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