Dynamics involving many electron systems
Multiple electron excitation and ionization of atoms and molecules by time-dependent external forces, such as ion impact and or an intense laser pulse, is of fundamental interest in understanding the strong electron-electron correlations in atoms and molecules. I investigated the processes involving He as the simplest many electron atom, such as auto ionization via double electron excitations (Auger processes) and double ionizations by energetic proton and antiproton impacts. There exist intrinsic difficulties in describing these processes beyond the first order perturbation theory (the first Born approximation) due to the high density of states and continuum-continuum coupling terms via the long range Coulomb interaction between electrons and incident ions. I developed a very efficient computer code by discretizing the single and double continuum states in the hyperspherical coordinates and carried out ab initio calculations for the first time. We showed that two electron transitions such as double electron excitations and double electron ionizations strongly depend on the charge sign of the incident ions. (There are no charge sign dependences in the first order perturbation, since the transition probabilities are proportional to the square of the charge state). We found this charge sign dependence in the cross sections is due to the quantum interference among the degenerate continuum states.
References
“Ab initio electron emission cross section of doubly excited He generated
by fast
proton and anti-proton impact”,
T. Morishita, K. Hino, S. Watanabe, and M. Matsuzawa,
J. Phys. B: At. Mol. Opt. Phys. 27, L287-L292 (1994)
“Double-electron
excitation of H－ by fast proton and antiproton impact”,
K. Hino, M. Nagase, H. Okamoto, T. Morishita, M.
Matsuzawa, and
M. Kimura,
Phys. Rev. A 49, 3753-3760 (1994)
“Proton-antiproton
impact-electron emission spectra of He: Comparison of theory with
experiment”,
T. Morishita, K. Hino, S. Watanabe, and M. Matsuzawa,
Phys. Rev. A53, 2345-2358 (1996)
“Hyperspherical
L2-integrable basis method for energetic proton and
anti-proton
impact autoionization”',
T. Morishita, K. Hino, T. Edamura, D. Kato, S. Watanabe
and M. Matsuzawa
J. Phys. B: At. Mol. Opt. Phys. 34, L475-L484 (2001)
“Double-ionization
of He by fast proton and antiproton impact”
T. Morishita, T. Sasajima, S. Watanabe, and M. Matsuzawa,
Nucl. Instrum. Methods B, 214, 144-148 (2004)