Energy transfer and quenching rates of laser-pumped electronically excited alkalis in flames

A pulsed, tunable dye laser has been used to excite each of the 3p, 3d, 4p, 5s and 4d levels of sodium atoms seeded into an atmospheric pressure acetylene-air flame. Three of these transitions, 3d, 5s and 4d, involve two-photon absorption from the ground 3s state. Fluorescence measurements furnish the populations of each of the levels populated by collisional transfer, enabling the deduction of relative energy transfer and quench rates among the four higher states. Fluorescence and opto-acoustic measurements under conditions near optical saturation of the 3p transition yield energy transfer rates and quenching rates for the two doublet components. Total collision-broadened linewidths are obtained by scanning the laser in a narrow-line mode. A qualitative experiment seeding the flame with both sodium and lithium suggests the presence of electronic-to-vibrational-to-electronic energy transfer.