Research Papers in Physics and Astronomy


Date of this Version

December 1987


Published by American Physical Society. Phys. Rev. A 36, 5280 (1987). Copyright © 1987 American Physical Society. Permission to use.


Helium atoms excited to an aligned (1s3d) 3D state are produced by electron impact parallel to a magnetic field. The initial alignment of the atomic state evolves into an orientation with finite angular momentum along the magnetic field direction and thus gives rise to a circularly polarized component in the (1s3d) 3D→(1s2p) 3P radiation propagating parallel to the magnetic field. Circular-polarization fractions of a few percent are observed, in general agreement with theory. The measured polarization fraction is found to be pressure dependent, indicating that secondary excitation and cascade processes must be included for a complete description.

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