THE 3D[-3P ENDOTHERMIC COLLISIONAL POPULATION TRANSFER OF LI IN HE AND AR AT 298 K

The 3p state of Li was excited in He and Ar buffer gases at room tempe rature (298 K) and the time profiles of sensitized fluorescence from t he 3s and 3d states were measured. The 3d <-- 3p endothermic populatio n transfer rates determined from the pressure dependence of the time p rofiles were 6.5 x 10(-11) cm(3) s(-1) for He and less than 10(-3) cm( 3) s(-1) for Ar. The origin of this large difference between He and Ar is discussed in terms of non-adiabatic transitions between the 3p and 3d molecular states of the Li-He and Li-Ar molecules. (C) 1997 Elsevi er Science B.V.