COLLISIONAL ENERGY-TRANSFER IN NA(4P-3D)-HE,H-2 COLLISIONS

We have investigated the direct collisional energy transfer process Na*(4p) + M --> Na*(3d) + M, where M=He,H2 under gas cell conditions. We have measured the temporal profiles of the Na(3d-3p) sensitized fluorescence as a function of quenching gas pressure and fit the profiles to a two-state rate equation model to obtain the quenching rate coefficients from the Na*(4p) state. The total energy transfer rate coefficient out of the 4p state for He is small [(0.5 +/- 0.2) X 10(-10) cm3/S]. The total quenching rate coefficient out of the 4p state is much larger for H-2[(3.9 +/- 0.5) X 10(-10) cm3/s]. Evidence suggests that the energy transfer rate coefficient for the 4p-3d process is approximately 2.0 X 10(-10) cm3/S With the remainder of the 4p quenching being predominantly reactive. We also compare the far-red wing absorption line shapes for the NaHe and NaH2 systems.