Fine Structure and Diamagnetic Zeeman Effect in He (4P3)

Abstract

The $4^{3}P$ state of helium has been excited and aligned by electron impact in a strong magnetic field. Transitions between Zeeman levels of the fine-structure states are induced by microwave frequency radiation and are detected through the resulting change in polarization of 3188-\AA{} fluorescence. The derived values of the fine-structure intervals are $4^{3}P_{0}\ensuremath{-}4^{3}P_{1}=3306.6\ifmmode\pm\else\textpm\fi{}1.0$ MHz and $4^{3}P_{1}\ensuremath{-}4^{3}P_{2}=270.7\ifmmode\pm\else\textpm\fi{}0.8$ MHz. The diamagnetic Zeeman interaction produces an observable effect, and the magnitude of its anisotropic part has been measured. The atomic radius and quadrupole moment are derived from this measurement and agree within experimental error with the values for a hydrogenic $4p$ orbital.