NaCd excimer emission bands

Abstract The analysis of the visible spectrum of a high pressure sodium lamp filled with sodium, cadium and xenon revealed the existence of NaCd excimer spectral features. These are four red satellite bands at 691, 697, 709 and 726.5 nm and diffuse bands peaking at 479.1 and 484.3 nm. Both spectral phenomena are related to those found earlier for the NaHg system. An interpretation of the red satellite bands origin is given in terms of a qualitative model for the four lowest potential curves of the NaCd excimer. In this model the essential feature is the avoided crossing between B 2 ∑ 1/2 and A 2 ∏ 1/2 electronic states, which causes a complex structure of the satellite bands in the very far red wing of the sodium D lines broadened by cadmium.