Berlin 2001 – wissenschaftliches Programm
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MO: Molekülphysik
MO 4: Posters Tuesday: Photoionisation
MO 4.2: Poster
Dienstag, 3. April 2001, 12:30–15:00, AT3
Non Franck-Condon effects in the photoionization of molecular oxygen to the O2+ X 2Πg state and of molecular nitrogen to the N2+ A 2Πu state in the 19 - 34 eV photon energy range. — •Jaume Rius i Riu1, Marek Stankiewicz2, Piotr Winiarczyk2, Andrzej Karawajczyk1, Leif Veseth3, and Peter Erman1 — 1Section of Atomic and Molecular Physics, Department of Physics, Royal Institute of Technology, SE 10044 Stockholm, Sweden — 2Instytut Fizyki im. Mariana Smoluchowskiego, Uniwersytet Jagiellonski, ul. Reymonta 4, 30-059 Krakow, Poland — 3Department of Physics, University of Oslo, N-0316 Oslo, Norway
Photoionization to the O2+ X 2Πg state and to the N2+ A 2Πu state is studied using photoelectron spectroscopy.
In the case of molecular oxygen, the experimental vibrational branching ratios for the v = 0 - 3 levels are obtained in the 19 - 31 eV region which show strong non Franck-Condon effects. Using ab initio many body perturbation theory branching ratios, vibrationally resolved partial cross sections and total cross section for the ionization to the X 2Πg state are calculated. Molecular states which autoionize to the O2+ X 2Πg state continuum are discussed. Photoionization of the O2 πg electron is not fully explained by channel coupling effects and autoionization from known Rydberg series and valence states.
In the case of molecular nitrogen, the experimental branching ratios for the v = 0 - 3 levels obtained for the first time in the 20 - 34 eV region, show strong non Franck-Condon effects around 22 eV. Using ab initio many body perturbation theory branching ratios for ionization to the A 2Πu state are calculated. This study indicates that the Franck-Condon breakdown in the photoionization of the N2 1πu electron is due to autoionization from Rydberg and valence states of N2.