Study of the optical emission in collisions between sodium and noble-gas atoms in the energy range between 10 and 500 eV

A complete set of data obtained from the collision-induced emission of the Na resonance lines is presented for Na-noble-gas collisions. The data include the emission cross sections and the polarisation fractions of the Na 3 2 P 3/2 to 3 2 S 1/2 resonance line, and the ratio of the cross sections for emission of the two resonance lines as a function of the collision energy, measured between the apparent thresholds and about 500 eV collision energy. Cross sections for ultraviolet emission by the noble-gas atoms have been measured in the same energy range. Except for Na-Ne, excitation of the noble-gas atom is relatively unimportant compared to the Na excitation. A qualitative interpretation of the results is attempted on the basis of molecular-orbital energy diagrams.