Berlin 2005 – wissenschaftliches Programm
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A: Atomphysik
A 1: Photoionisation
A 1.1: Hauptvortrag
Freitag, 4. März 2005, 10:15–10:45, HU 3075
Partial cross sections and β-parameters of doubly excited helium — •R Püttner1, Y. H. Jiang1,2, M. Braune3, R. Hentges3, J. Viefhaus3, M. Poiguine1, U. Becker3, J.-M. Rost2, and G Kaindl1 — 1Freie Universität Berlin, D-14195 Berlin — 2Max-Planck-Institut für Physik Komplexer Systeme, D-01187 Dresden — 3Fritz-Haber Institut Berlin, D-14195 Berlin
Partial photoionization cross sections (PCSs), σn, leading to final ionic states of helium, He+(n), were measured at BESSY II in the region of doubly excited helium up to the ionization threshold I9 of He+. The experiments were performed with a time-of-flight (TOF) electron spectrometer and high photon resolution, Δ E≅ 6 meV. The results of these measurements are a most critical assessment of the decay dynamics of double-excitation resonances and agree well with those of recent eigenchannel R-matrix calculations. They also confirm the propensity rules [1] set up for the autoionization of double-excitation states. The mirroring behavior in the PCSs predicted recently by Liu and Starace [2] can be understood in a more general context. Preliminary results on angle-resolved measurements below the I5 and I6 will also be displayed.
[1] J. M. Rost et al., J. Phys. B 30, 4663 (1997). [2] Ch.-N. Liu and A. Starace, Phys. Rev. A 59, R1731 (1999).