Knowledge Bank

Laser excitation of $Cs2$ vapor in the 4600-5200 {\AA} region gives a complex fluorescence spectrum which is partly discrete and partly diffuse. The fluorescence terminates in a series of characteristic diffuse bands near 6100 {\AA} which display structure reminiscent of that observed in previously analyzed bound-free systems In $I2$. The overall intensity of these features in fluorescence tracks approximately the absorption cross section in the 4600-5200 {\AA} region. By assuming that the absorption and fluorescence involve only one upper and one lower (X) state, we are able to deduce an approximate potential curve for the excited state which can account for both processes. This curve is very ``open” with $\omega e\approx 15cm-1$ and $Re\approx 6.6Aˇ$ -- which helps explain the incredible complexity of the 4800 {\AA} absorption system.