Cross sections for the Na.4D/! Na.4F/ excitation energy transfer induced by collisions with He, Ar and Na atoms

The cross sections for the Na.4D/! Na.4F/ excitation energy transfer induced by collisions with He, Ar and Na ground-state atoms have been measured. The sodium atoms in the 4D state have been produced by two-photon excitation using cw laser radiation at 578.89 nm. Within a model which takes into account collisional population and depopulation of the 4F level as well as radiative relaxation (direct or cascade) of the 3D, 4P, 4D and 4F states ending in the 3P level, the rate for the Na.4D/ ! Na.4F/ collisional transfer turns out to be related to the ratio of the steady-state populations created in 3D and 4D states. They have been determined by measuring the fluorescence intensities of the 3D ! 3P and 4D! 3P transitions. The measurements yield the following cross section values for those processes investigated: Na He 4D!4F D.60 10/ 10