Fluorescence polarization of helium negative-ion resonances excited by polarized electron impact

Authors

• J. W. Maseberg, University of Nebraska - Lincoln
• Timothy J. Gay, University of Nebraska - LincolnFollow

Document Type

Article

Date of this Version

November 2006

Comments

Published in Journal of Physics B: Atomic, Molecular and Optical Physics 39 (2006) 4861–4870. Copyright © 2006 IOP Publishing Ltd. Used by permission. Online at http://stacks.iop.org/JPhysB/39/4861

Abstract

We have investigated helium (1s3d) ³D → (1s2p) ³P (588 nm) fluorescence produced by electron impact excitation in the vicinity of the (2s²2p) ²P and (2s2p²) ²D negative-ion resonances at 57.2 and 58.3 eV, respectively. In contrast to previous work, we use spin-polarized incident electrons and report the relative Stokes parameters P₁, P₂, and P₃ in the 55–60 eV region. Our failure to see discernable resonance effects in P₂ indicates that even though the lifetime of these resonances is significant (~10 fs), magnetic forces acting on the temporarily captured electron are small. Resonant structures in the values of P₁ and P₃ are observed because the polarization contributions of resonant states are generally different than those from direct excitation of the 3 ³D state.