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Abstract

The nuclear motion and geometry in core-excited CO2 are probed using a multiple-ion-coincidence imaging technique. We demonstrate that CO2 has a linear stable geometry in the C/O 1s−1 core-ionized state and a bent geometry in the C/O 1s−1π* core-excited state. The molecules in the C/O 1s−1π* A1 and B1 Renner–Teller states are probed to be bent in the A1 state and linear in the B1 state. The Osingle bondO correlation angle distributions are well reproduced using a Coulomb explosion model which takes account of the zero point bending motion in the ground state, the classical bending motion along the potential energy curve of the core-excited state within the core-hole lifetime and the initial inhomogeneous charge distribution in the multiply charged molecular ion just before the dissociation. When the photon energy is tuned to be higher (lower) energy than the 1s−1π* resonance center, the events for the 1s−1π* A1 states that result in the low Osingle bondO correlation angle distribution are suppressed (enhanced).