Measurement of atomic densities using radiation trapping

The apparent lifetimes of the 2P1/2 and 2P3/2 states of Na have been measured as functions of n, the atomic density, and the results compared to theory. It is shown that these measurements made under equilibrium, steady-state conditions may be used to determine n under nonequilibrium, nonsteady-state conditions. This technique of measuring n has advantages over the surface ionization technique, especially for values of n greater than about 1010 cm−3. Extension of the technique to other atoms and molecules is discussed.