EXCITATION AND IONIZATION-EXCITATION OF HELIUM FOLLOWING ELECTRON AND
PROTON IMPACT: A POLARIZATION STUDY


H. Merabet*, A. Siems#, M. Bailey&, R. Bruch*, A. G. Trigueiros#


*Department of Physics, University of Nevada Reno, Reno NV 89557 USA
#Quantum Electronic Department, Physics Institute- UNICAMP, Campinas,
Brazil
&Atmospheric Science Center, Desert Research Institute (DRI), Reno NV
89506 USA


New experimental results are presented on measurements of the degree of
linear polarization for excitation and ionization-excitation of He
following proton impact.  In particular, polarization measurements for He
(1snp) 1P0, He+ (2p) 2P0, and He+ (3p) 2P0 states with transition
wavelengths of 51.7 to 58.4 nm, 30.4 nm, and 25.6 nm, respectively, have
been obtained for proton impact energies ranging from 100 keV to 1 MeV.
Furthermore, these results are compared with recent polarization
measurements following electron impact on He for the same range of
velocities.