COHERENT OPTICAL TRANSIENT MEASUREMENTS OF ABSOLUTE AND DIFFERENTIAL STARK SHIFTS IN ATOMIC SODIUM

A coherent optical transient technique has been used for the first time to study the Stark effect in atoms. This technique involves the recording of transients in the intensity of single-mode laser radiation transmitted by an atomic vapour following the sudden application of an electric-field pulse. It allows both absolute and differential Stark shifts to be measured to a precision which is limited only by the power-broadened natural linewidth of the transition. The feasibility of this technique is demonstrated by measuring the scalar ( alpha 0) and tensor ( alpha 2) polarisabilities associated with the sodium 32P1/2 and 32P 3/2 levels of sodium. The resolution is such that the effect of the hyperfine structure on the Stark shifts has to be included in the analysis. Our values for the polarisabilities are alpha 0=0+or-3.3 kHz (kV cm -1)-2 and alpha 2=28.1+or-3.9 KHz (kV cm -1)-2. These results are compared with experimental and theoretical values obtained by other authors.