Berlin 2001 – scientific programme
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A: Atomphysik
A 1: Posters Monday (Cluster, Atoms in Fields)
A 1.35: Poster
Monday, April 2, 2001, 12:30–15:00, AT3
STATISTICAL PROPERTIES OF INTER-SERIES MIXING IN HELIUM: FROM INTEGRABILITY TO CHAOS — •R. Püttner1, B. Grémaud2, D. Delande2, M. Domke1, M. Martins1, A. S. Schlachter3, and G. Kaindl1 — 1Institut für Experimentalphysik, Freie Universität Berlin, Germany — 2Laboratoire Kastler-Brossel, Université Pierre et Marie Curie, Paris, France — 3Lawrence Berkeley National Laboratory, Berkeley, CA, USA
We present high-resolution photoabsorption spectra of 1Po doubly excited states in helium below the N=9 ionization threshold and the calculated photoionzation cross section in the same energy region. Based on the excellent agreement between experiment and theory, we performed a statistical analysis of the nearest neighbor spacing (NNS) using the theoretical results to study the transition from integrability to chaos. The NNS distribution was determined in two different ways: (i) by considering all spacings and (ii) by considering only the spacings between resonances that belong to the same Rydberg series N,Kn (with N (n) being the quantum number of the inner (outer) electron and K the angular correlation quantum number). In the first case the NNS distribution reveals a Poisson distribution that is typical for a regular system, while in the second case a development of the NNS distribution towards a Wigner distribution − which is typical for chaotic systems − can be found. In addition, 1 dimensional (1D) stretched helium is studied theoretically below the N=9, 13, and 17 ionization threshold revealing that the NNS distribution develops clearly towards a Wigner distribution with increasing N.