Inelastic collisions between excited alkali atoms and molecules. V. Sensitized fluorescence in mixtures of sodium with N₂, H₂, HD, and D₂

3 2 P 1/2 ↔ 3 2 P 3/2 excitation transfer in sodium, induced in inelastic collisions with ground-state N 2 , H 2 , HD, and D 2 molecules, has been investigated in a series of sensitized fluorescence experiments. Mixtures of sodium vapor at a pressure of 5 × 10 −7 Torr, and the gases, were irradiated with each Na D component in turn, and the fluorescence which contained both D components was monitored at right angles to the direction of the exciting beam. Measurements of the relative intensities of the Na D fluorescent components yielded the following collision cross sections for excitation transfer. For Na–N 2 collisions: Q 12 ( 2 P 1/2 → P 3/2 ) = 144 Å 2 , Q 21 ( 2 P 1,2 ← 2 P 3/2 ) = 76 Å 2 for Na–H 2 collisions: Q 12 = 80 Å 2 , Q 21 = 42 Å 2 . For Na–HD collisions: Q 12 = 84 Å 2 , Q 21 = 44 Å 2 . For Na–D 2 collisions: Q 12 = 98 Å 2 , Q 21 = 52 Å 2 . The cross sections Q 21 exhibit a slight resonance effect between the atomic and molecular rotational transitions.