A study of collisional broadening of the Na D lines by neon and xenon perturbers. I. The line core

Using a well known semiclassical theory the authors calculated the width and shift of the Na D lines as well as the cross sections for fine-structure mixing and depolarisation on the basis of the Na-Xe potentials from Czuchaj and Sienkiewicz (1979). The results of this model were found to be in good agreement with the fully quantal values obtained by de Vries for this system. The authors discuss possible sources of error in the cross sections due to this physical model, the adopted interaction potentials and the numerical calculations. The broadening, shift and asymmetry of the Na D lines due to collisions with Ne and Xe atoms at 720 and 990 K were measured in a fluorescence cell. From the authors experimental data and results available in the literature on broadening, shift, fine structure and depolarisation, the authors evaluated several Na-Ne, Xe interaction potentials with this semiclassical model. They conclude that the best Na-Ne potentials in the internuclear region between about 5 and 13 AA are given by the X Sigma potential of Masnou-Seeuws et al and the A Sigma and B Sigma of Peach (1982). For Na-Xe the situation in the internuclear region between about 6 and 18AA is less satisfactory. Although the X Sigma potential is well known (Van Deventer and van der Valk), the A Sigma and B Sigma potentials that are currently available in the literature could not fully reproduce the experimental cross sections. However, a best set of potentials is given.