Direct Measurement of Atomic Lifetimes of Cesium and Sodium*

An apparatus has been developed which is capable of measuring radiative lifetimes for energy levels that can be reached in absorption. At present, lifetimes in the range 15 nsec to 5 μsec can be measured, but the range can be extended in both directions. The lifetime of the 7p P232 state of cesium is measured to be 111±6 nsec, in moderately good agreement with one previous determination and with a Bates–Damgaard calculation. The lifetime of the 3p2P states of sodium is measured to be 16.1 ± 1 nsec, in excellent agreement with other measurements.