Laser Spectroscopy of the Fine-Structure Splitting in the 2(3)P(J) Levels of He-4

摘要

The fine-structure splitting in the 2(3)P(J) (J = 0, 1, 2) levels of He-4 is of great interest for tests of quantum electrodynamics and for the determination of the fine-structure constant alpha. The 2(3)P(0)-2(3)P(2) and 2(3)P(1)-2(3)P(2) intervals are measured by laser spectroscopy of the P-3(J)-2(3)P(1) transitions at 1083 nm in an atomic beam, and are determined to be 31 908 130.98 +/- 0.13 kHz and 2 291 177.56 +/- 0.19 kHz, respectively. Compared with calculations, which include terms up to alpha(5)Ry, the deviation for the a-sensitive interval 2(3)P(0)-2(3)P(2) is only 0.22 kHz. It opens the window for further improvement of theoretical predictions and an independent determination of the fine-structure constant alpha with a precision of 2 x 10(-9).