Electronic Excitation in Fast Collisions of Na with SO2 and NO2

Abstract

A sputtered Na beam has been used to investigate collisionally induced electronic excitation in scattering with SO2 and NO2. Light from the radiative decay of excited electronic states was observed at several wavelengths, and measurements were made of the excitation cross sections as a function of the center-of-mass collision energy in the range 1–30 eV. In both scattering systems, the most intense light measured originated from the Na (32P→32S) D line. Light from the (42D→32P) Na transition was observed, but its intensity was more than an order of magnitude smaller than that of the D line. Emission also occurred from transitions with long radiative lifetimes (∼40 μsec). This emission is probably due to the B1→A1 molecular transitions of SO2 and NO2. The results have been discussed in terms of a potential curve-crossing mechanism which seems to satisfactorily explain collisionally induced alkali atom excitation. For the molecular emission, an alternate mechanism has also been considered which involves vibrational coupling of the A1 and B1 states.