Radiative Transition Line Shape in Warm and Dense Argon Plasma: a Two-Centre Model Study

A two-centre model is employed to study the electronic structure of argon plasma at a density of 10²²cm^-3 and a temperature of 5eV. The model takes into account the influence of the nearest neighbour on the electronic structure of the radiator and gives a proper description of the transient molecular behaviour in dense plasmas where the mean interatomic distance can be the order of the orbital spatial extent. The orbital energies of quasi-molecular Ar₂ against the interatomic distance are calculated in the framework of density functional theory. It is shown that the orbital energies are not monotonic functions of the distance because of two competitive effects: the repulsive potential between electrons and the attractive potential between electrons and nuclei. The characteristics of this two-centre system can be categorized by three regimes depending on the ratio between the electron wavelength and the interatomic distance: atomic regime, screened atomic regime, and quasi-molecular regime. This classification agrees qualitatively with the conclusion of full quantum-mechanical approach Yonger S M et al 1988 Phys. Rev. Lett. 61 962.