https://doi.org/10.1140/epjd/e2002-00219-7
A novel electron scattering apparatus combining a laser photoelectron source and a triply differentially pumped supersonic beam target: characterization and results for the He-(1s 2s2) resonance
1
Fachbereich Physik, Universität Kaiserslautern, D-67653 Kaiserslautern, Germany
2
ITAMP, Harvard Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
Corresponding author: a hotop@physik.uni-kl.de
Received:
23
July
2002
Published online:
29
October
2002
A novel electron scattering apparatus for high resolution studies of angle-differential elastic
and inelastic electron scattering from atoms and molecules in the gas phase is described and
its performance characterized. It combines a laser photoelectron source, a triply differentially
pumped collimated supersonic beam target (half angle 0.015 rad, background to beam density
ratio <0.01), and several electron multipliers for simultaneous detection of elastically
scattered electrons and metastable atoms (or molecules) due to inelastic scattering. In detailed
test measurements of the yield for the production of metastable He*(23S1) atoms around its
threshold, the dependence of the overall energy width on various experimental parameters has
been investigated. So far a resolution down to 7 meV (FWHM) has been obtained. Under
such conditions we have investigated the profile of the He-
resonance at the scattering angles 22°, 45°, and 90°. From a consistent fit of the measured profiles by resonant
scattering theory we determine a new value for the resonance energy (
eV) and
an accurate resonance width (
meV). These results are consistent with the
previously recommended values.
PACS: 39.10.+j – Atomic and molecular beam sources and techniques / 41.75.Fr – Electron and positron beams / 34.80.Bm – Elastic scattering of electrons by atoms and molecules / 34.80.Dp – Atomic excitation and ionization by electron impact
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2003