Neutral helium spectral lines in dense plasmas.

Shift and broadening of isolated neutral helium lines 7281 angstroms (2(1)P-3(1)S), 7065 angstroms (2(3)P-3(3)S), 6678 angstroms (2(1)P-3(1)D), 5048 angstroms (2(1)P-4(1)S), 4922 angstroms (2(1)P-4(1)D), and 4713 angstroms (2(3)P-4(3)S) in a dense plasma are investigated. Based on a quantum statistical theory, the electronic contributions to the shift and width are considered, using the method of thermodynamic Green functions. Dynamic screening of the electron-atom interaction is included. Compared to the width, the electronic shift is more affected by dynamical screening. This effect increases at high density. A cut-off procedure for strong collisions is used. The contribution of the ions is taken into account in a quasi-static approximation, with both the quadratic Stark effect and the quadrupole interaction included. The results for shift and width agree well with the available experimental and theoretical data.