Berlin 2001 – scientific programme
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A: Atomphysik
A 5: Posters Tuesday (Photoionisation, Multi Photon Processes)
A 5.11: Poster
Tuesday, April 3, 2001, 12:30–15:00, AT3
Single photoionization of helium close to the double-ionization threshold — •Tobias Schneider1, Chien-Nan Liu2, and Jan-Michael Rost1 — 1Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany — 2Kansas State University, Manhattan, Kansas, USA
We investigate the 1P o double-excitation resonances of the helium atom close to the double-ionization threshold. Eigenchannel R-matrix calculations for total and partial photoionization cross sections are presented.
The low-lying Rydberg series of resonance states can be classified by means of approximate quantum numbers [1]. However, in the higher energy region, Rydberg series associated with different thresholds overlap, leading to the breakdown of this classification scheme. Therefore, a spectroscopic analysis of the cross section on the basis of individual resonances is no longer valid. It was estimated [2] that already above the He+(N=15) threshold the cross section is dominated by irregular, random-like fluctuations, so-called Ericson fluctuations. Our calculations up to the eleventh threshold enable us to analyze the transitional regime from regular to irregular behavior.
[1] G. Tanner, K. Richter, and J.-M. Rost, Rev. Mod. Phys. 72, 497 (2000)
[2] J. Burgdörfer, Y. Qiu, and J. Müller, in Classical, Semiclassical and Quantum Dynamics in Atoms, edited by H. Friedrich and B. Eckhardt (Springer-Verlag, Berlin) 1997, p. 304