Bonn 2000 – scientific programme
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A: Atomphysik
A 3: Elektronenstöße
A 3.7: Talk
Monday, April 3, 2000, 18:00–18:15, HS I
Negative ion resonances in slow electron-heavy alkali atom scattering — •Uwe Thumm1,2 and Cristian Bahrim1 — 1Dept. of Physics, Kansas State University, Manhattan, KS 66506, USA — 2Fak. f. Physik, Univ. Freiburg, Hermann-Herder Str. 3, 79104 Freiburg
Our Dirac R–matrix calculations suggest that none of the heavy alkali
negative ions, Rb [1], Cs [1,2], and Fr [1], has an excited bound state.
Their lowest excited state appears to be a multiplet of triplett P (odd parity)
shape resonances, the J=1 fine – structure component of which was recently
observed in photodetachment experiments on negative Cs ions. We carefully
analyzed these and other low–lying excited heavy alkali negative
ion states in partial and converged total scattering cross sections for
electrons with incident kinetic energies below 2.8 eV. Our results
agree well with available experimental data. We propose a new
value for the electron affinity of Fr, provide the scattering length for
electronic collisions with Rb, Cs, and Fr, and discuss the nuclear
charge–dependence of relativistic effects in the resonance profiles.
[1] C. Bahrim and U. Thumm, Phys. Rev. A. (February 2000)
[2] U. Thumm, Book of Invited Papers, XVIII ICPEAC, Aarhus, Dk, 263 (1993).