LASER SPECTROSCOPY ON THE STARK-EFFECT OF THE 1S3P P-3 LEVEL OF HE-I

In electric fields 0 less than or equal to F less than or equal to 160 kV cm(-1), shift and splitting of the lambda(1s2s S-3-1s3p P-3) = 389 nm line of He I were measured spectroscopically by crossing a beam of metastable He atoms with a frequency-doubled cw Ti:sapphire laser bea m. We deduced the difference Delta alpha(sc) = alpha(sc)(3 P-3) - alph a sc(2 S-3) = 4.20(3) MHz (kV cm(-1))(-2) of the scalar polarizabiliti es, the tensor polarizability alpha(ten)(3 P-3) = 84.0(7) kHz (kV cm(- 1))(-2) and the energy separation of closest approach h nu(min) = E(3 P-3(0), 0(-)) - E(3 P-3(2), 0(-)) = 8257(5) MHz . h of the Stark suble vels with m = 0 and negative reflection parity at F = 154(3) kV cm(-1) . The polarizabilities agree with calculated values. By comparing the measured energy separation with theory, we deduced that the scalar pol arizabilities of the P-3(2) and P-3(0) differ slightly by {alpha(sc)(P -3(2)) - alpha(sc)(P-3(0))}/alpha(sc)(P-3) = (1.8 +/- 1.2) X 10(-4).