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Free keywords:
carbon dimer anion
photon-ion merged-beams method
inner-shell photoabsorption
Franck-Condon analysis
molecular potential curves
Abstract:
Carbon 1s core-hole excitation of the molecular anion C2- has been experimentally studied at high resolution by employing the photon-ion merged-beams technique at a synchrotron light source. The experimental cross section for photo–double-detachment shows a pronounced vibrational structure associated with 1σu ->3σg and 1σg ->1πu core excitations of the C2- ground level and first excited level, respectively. A detailed Franck-Condon analysis reveals a strong contraction of the C2- molecular anion by 0.2 Å upon this core photoexcitation. The associated change of the molecule's moment of inertia leads to a noticeable rotational broadening of the observed vibrational spectral features. This broadening is accounted for in the present analysis which provides the spectroscopic parameters of the C2- 1σu-13σg2 2∑u+ and
1σg-13σg2 2∑g+ core-excited levels.
