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In electric fields 0 F 160 kV cm −1 , shift and splitting of the λ(1s2s 3 S-1s3p 3 P) = 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 beam. We deduced the difference α sc = α sc (3 3 P) − α sc (2 3 S) = 4.20(3) MHz (kV cm −1 ) −2 of the scalar polarizabilities, the tensor polarizability α ten (3 3 P) = 84.0(7) kHz (kV cm −1 ) −2 and the energy separation of closest approach hν min = E(3 3 P 0 , 0 − ) − E(3 3 P 2 , 0 − ) = 8257(5) MHz • h of the Stark sublevels 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 polarizabilities of the 3 P 2 and 3 P 0 differ slightly by {α sc ( 3 P 2 ) − α sc ( 3 P 0 )}/α sc ( 3 P) = (1.8 ± 1.2) × 10 −4 .

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